diff --git a/dev/bots/analyze-sample-code.dart b/dev/bots/analyze-sample-code.dart
index 5974d4b019..ecc1491c4a 100644
--- a/dev/bots/analyze-sample-code.dart
+++ b/dev/bots/analyze-sample-code.dart
@@ -100,13 +100,13 @@ const String kDartDocPrefix = '///';
 const String kDartDocPrefixWithSpace = '$kDartDocPrefix ';
 
 Future<Null> main() async {
-  final Directory temp = Directory.systemTemp.createTempSync('analyze_sample_code_');
+  final Directory tempDir = Directory.systemTemp.createTempSync('flutter_analyze_sample_code.');
   int exitCode = 1;
   bool keepMain = false;
   final List<String> buffer = <String>[];
   try {
-    final File mainDart = new File(path.join(temp.path, 'main.dart'));
-    final File pubSpec = new File(path.join(temp.path, 'pubspec.yaml'));
+    final File mainDart = new File(path.join(tempDir.path, 'main.dart'));
+    final File pubSpec = new File(path.join(tempDir.path, 'pubspec.yaml'));
     final Directory flutterPackage = new Directory(path.join(_flutterRoot, 'packages', 'flutter', 'lib'));
     final List<Section> sections = <Section>[];
     int sampleCodeSections = 0;
@@ -210,7 +210,7 @@ dependencies:
     final Process process = await Process.start(
       _flutter,
       <String>['analyze', '--no-preamble', '--no-congratulate', mainDart.parent.path],
-      workingDirectory: temp.path,
+      workingDirectory: tempDir.path,
     );
     stderr.addStream(process.stderr);
     final List<String> errors = await process.stdout.transform<String>(utf8.decoder).transform<String>(const LineSplitter()).toList();
@@ -285,7 +285,7 @@ dependencies:
       print('No errors!');
   } finally {
     if (keepMain) {
-      print('Kept ${temp.path} because it had errors (see above).');
+      print('Kept ${tempDir.path} because it had errors (see above).');
       print('-------8<-------');
       int number = 1;
       for (String line in buffer) {
@@ -295,10 +295,9 @@ dependencies:
       print('-------8<-------');
     } else {
       try {
-        temp.deleteSync(recursive: true);
+        tempDir.deleteSync(recursive: true);
       } on FileSystemException catch (e) {
-        // ignore errors deleting the temporary directory
-        print('Ignored exception during tearDown: $e');
+        print('Failed to delete ${tempDir.path}: $e');
       }
     }
   }
diff --git a/dev/bots/prepare_package.dart b/dev/bots/prepare_package.dart
index d323f877f2..cbaf1e2584 100644
--- a/dev/bots/prepare_package.dart
+++ b/dev/bots/prepare_package.dart
@@ -640,7 +640,7 @@ Future<Null> main(List<String> argList) async {
   Directory tempDir;
   bool removeTempDir = false;
   if (args['temp_dir'] == null || args['temp_dir'].isEmpty) {
-    tempDir = Directory.systemTemp.createTempSync('flutter_');
+    tempDir = Directory.systemTemp.createTempSync('flutter_package.');
     removeTempDir = true;
   } else {
     tempDir = new Directory(args['temp_dir']);
diff --git a/dev/bots/test.dart b/dev/bots/test.dart
index 09e66f5f79..61e3c049c3 100644
--- a/dev/bots/test.dart
+++ b/dev/bots/test.dart
@@ -191,7 +191,7 @@ Future<Null> _analyzeRepo() async {
   await _checkForTrailingSpaces();
 
   // Try analysis against a big version of the gallery; generate into a temporary directory.
-  final String outDir = Directory.systemTemp.createTempSync('mega_gallery').path;
+  final Directory outDir = Directory.systemTemp.createTempSync('flutter_mega_gallery.');
 
   try {
     await _runCommand(dart,
@@ -199,17 +199,13 @@ Future<Null> _analyzeRepo() async {
         '--preview-dart-2',
         path.join(flutterRoot, 'dev', 'tools', 'mega_gallery.dart'),
         '--out',
-        outDir,
+        outDir.path,
       ],
       workingDirectory: flutterRoot,
     );
-    await _runFlutterAnalyze(outDir, options: <String>['--watch', '--benchmark']);
+    await _runFlutterAnalyze(outDir.path, options: <String>['--watch', '--benchmark']);
   } finally {
-    try {
-      new Directory(outDir).deleteSync(recursive: true);
-    } catch (e) {
-      // ignore
-    }
+    outDir.deleteSync(recursive: true);
   }
 
   print('${bold}DONE: Analysis successful.$reset');
diff --git a/dev/bots/test/common.dart b/dev/bots/test/common.dart
index b36d043b0a..7638adba37 100644
--- a/dev/bots/test/common.dart
+++ b/dev/bots/test/common.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:io';
+
 import 'package:test/test.dart' hide TypeMatcher, isInstanceOf;
 import 'package:test/test.dart' as test_package show TypeMatcher;
 
@@ -12,3 +14,14 @@ export 'package:test/test.dart' hide TypeMatcher, isInstanceOf;
 
 /// A matcher that compares the type of the actual value to the type argument T.
 Matcher isInstanceOf<T>() => new test_package.TypeMatcher<T>(); // ignore: prefer_const_constructors, https://github.com/dart-lang/sdk/issues/32544
+
+void tryToDelete(Directory directory) {
+  // This should not be necessary, but it turns out that
+  // on Windows it's common for deletions to fail due to
+  // bogus (we think) "access denied" errors.
+  try {
+    directory.deleteSync(recursive: true);
+  } on FileSystemException catch (error) {
+    print('Failed to delete ${directory.path}: $error');
+  }
+}
diff --git a/dev/bots/test/prepare_package_test.dart b/dev/bots/test/prepare_package_test.dart
index bfeb9e4e9c..1da66ea592 100644
--- a/dev/bots/test/prepare_package_test.dart
+++ b/dev/bots/test/prepare_package_test.dart
@@ -67,7 +67,7 @@ void main() {
     });
     group('ArchiveCreator for $platformName', () {
       ArchiveCreator creator;
-      Directory tmpDir;
+      Directory tempDir;
       Directory flutterDir;
       FakeProcessManager processManager;
       final List<List<String>> args = <List<String>>[];
@@ -82,12 +82,12 @@ void main() {
         processManager = new FakeProcessManager();
         args.clear();
         namedArgs.clear();
-        tmpDir = await Directory.systemTemp.createTemp('flutter_');
-        flutterDir = new Directory(path.join(tmpDir.path, 'flutter'));
+        tempDir = Directory.systemTemp.createTempSync('flutter_prepage_package_test.');
+        flutterDir = new Directory(path.join(tempDir.path, 'flutter'));
         flutterDir.createSync(recursive: true);
         creator = new ArchiveCreator(
-          tmpDir,
-          tmpDir,
+          tempDir,
+          tempDir,
           testRef,
           Branch.dev,
           processManager: processManager,
@@ -99,16 +99,11 @@ void main() {
       });
 
       tearDown(() async {
-        // On Windows, the directory is locked and not able to be deleted yet. So
-        // we just leave some (very small, because we're not actually building
-        // archives here) trash around to be deleted at the next reboot.
-        if (!platform.isWindows) {
-          await tmpDir.delete(recursive: true);
-        }
+        tryToDelete(tempDir);
       });
 
       test('sets PUB_CACHE properly', () async {
-        final String createBase = path.join(tmpDir.absolute.path, 'create_');
+        final String createBase = path.join(tempDir.absolute.path, 'create_');
         final Map<String, List<ProcessResult>> calls = <String, List<ProcessResult>>{
           'git clone -b dev https://chromium.googlesource.com/external/github.com/flutter/flutter': null,
           'git reset --hard $testRef': null,
@@ -116,7 +111,7 @@ void main() {
           'git describe --tags --abbrev=0': <ProcessResult>[new ProcessResult(0, 0, 'v1.2.3', '')],
         };
         if (platform.isWindows) {
-          calls['7za x ${path.join(tmpDir.path, 'mingit.zip')}'] = null;
+          calls['7za x ${path.join(tempDir.path, 'mingit.zip')}'] = null;
         }
         calls.addAll(<String, List<ProcessResult>>{
           '$flutter doctor': null,
@@ -128,7 +123,7 @@ void main() {
           '$flutter create --template=plugin ${createBase}plugin': null,
           'git clean -f -X **/.packages': null,
         });
-        final String archiveName = path.join(tmpDir.absolute.path,
+        final String archiveName = path.join(tempDir.absolute.path,
             'flutter_${platformName}_v1.2.3-dev${platform.isLinux ? '.tar.xz' : '.zip'}');
         if (platform.isWindows) {
           calls['7za a -tzip -mx=9 $archiveName flutter'] = null;
@@ -151,7 +146,7 @@ void main() {
       });
 
       test('calls the right commands for archive output', () async {
-        final String createBase = path.join(tmpDir.absolute.path, 'create_');
+        final String createBase = path.join(tempDir.absolute.path, 'create_');
         final Map<String, List<ProcessResult>> calls = <String, List<ProcessResult>>{
           'git clone -b dev https://chromium.googlesource.com/external/github.com/flutter/flutter': null,
           'git reset --hard $testRef': null,
@@ -159,7 +154,7 @@ void main() {
           'git describe --tags --abbrev=0': <ProcessResult>[new ProcessResult(0, 0, 'v1.2.3', '')],
         };
         if (platform.isWindows) {
-          calls['7za x ${path.join(tmpDir.path, 'mingit.zip')}'] = null;
+          calls['7za x ${path.join(tempDir.path, 'mingit.zip')}'] = null;
         }
         calls.addAll(<String, List<ProcessResult>>{
           '$flutter doctor': null,
@@ -171,7 +166,7 @@ void main() {
           '$flutter create --template=plugin ${createBase}plugin': null,
           'git clean -f -X **/.packages': null,
         });
-        final String archiveName = path.join(tmpDir.absolute.path,
+        final String archiveName = path.join(tempDir.absolute.path,
             'flutter_${platformName}_v1.2.3-dev${platform.isLinux ? '.tar.xz' : '.zip'}');
         if (platform.isWindows) {
           calls['7za a -tzip -mx=9 $archiveName flutter'] = null;
@@ -182,8 +177,8 @@ void main() {
         }
         processManager.fakeResults = calls;
         creator = new ArchiveCreator(
-          tmpDir,
-          tmpDir,
+          tempDir,
+          tempDir,
           testRef,
           Branch.dev,
           processManager: processManager,
@@ -214,17 +209,11 @@ void main() {
 
       setUp(() async {
         processManager = new FakeProcessManager();
-        tempDir = await Directory.systemTemp.createTemp('flutter_');
-        tempDir.createSync();
+        tempDir = Directory.systemTemp.createTempSync('flutter_prepage_package_test.');
       });
 
       tearDown(() async {
-        // On Windows, the directory is locked and not able to be deleted yet. So
-        // we just leave some (very small, because we're not actually building
-        // archives here) trash around to be deleted at the next reboot.
-        if (!platform.isWindows) {
-          await tempDir.delete(recursive: true);
-        }
+        tryToDelete(tempDir);
       });
 
       test('calls the right processes', () async {
diff --git a/dev/devicelab/bin/tasks/gradle_plugin_test.dart b/dev/devicelab/bin/tasks/gradle_plugin_test.dart
index 70eacefdb6..7e218189f8 100644
--- a/dev/devicelab/bin/tasks/gradle_plugin_test.dart
+++ b/dev/devicelab/bin/tasks/gradle_plugin_test.dart
@@ -14,25 +14,25 @@ String errorMessage;
 
 /// Runs the given [testFunction] on a freshly generated Flutter project.
 Future<void> runProjectTest(Future<void> testFunction(FlutterProject project)) async {
-  final Directory tmp = await Directory.systemTemp.createTemp('gradle');
-  final FlutterProject project = await FlutterProject.create(tmp, 'hello');
+  final Directory tempDir = Directory.systemTemp.createTempSync('flutter_devicelab_gradle_plugin_test.');
+  final FlutterProject project = await FlutterProject.create(tempDir, 'hello');
 
   try {
     await testFunction(project);
   } finally {
-    project.parent.deleteSync(recursive: true);
+    rmTree(tempDir);
   }
 }
 
 /// Runs the given [testFunction] on a freshly generated Flutter plugin project.
 Future<void> runPluginProjectTest(Future<void> testFunction(FlutterPluginProject pluginProject)) async {
-  final Directory tmp = await Directory.systemTemp.createTemp('gradle');
-  final FlutterPluginProject pluginProject = await FlutterPluginProject.create(tmp, 'aaa');
+  final Directory tempDir = Directory.systemTemp.createTempSync('flutter_devicelab_gradle_plugin_test.');
+  final FlutterPluginProject pluginProject = await FlutterPluginProject.create(tempDir, 'aaa');
 
   try {
     await testFunction(pluginProject);
   } finally {
-    pluginProject.parent.deleteSync(recursive: true);
+    rmTree(tempDir);
   }
 }
 
diff --git a/dev/devicelab/bin/tasks/module_test.dart b/dev/devicelab/bin/tasks/module_test.dart
index 75ee57a293..88a35fe8cd 100644
--- a/dev/devicelab/bin/tasks/module_test.dart
+++ b/dev/devicelab/bin/tasks/module_test.dart
@@ -4,6 +4,7 @@
 
 import 'dart:async';
 import 'dart:io';
+
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/framework/utils.dart';
 import 'package:path/path.dart' as path;
@@ -22,9 +23,9 @@ Future<Null> main() async {
 
     section('Create Flutter module project');
 
-    final Directory directory = await Directory.systemTemp.createTemp('module');
+    final Directory tempDir = Directory.systemTemp.createTempSync('flutter_module_test.');
     try {
-      await inDirectory(directory, () async {
+      await inDirectory(tempDir, () async {
         await flutter(
           'create',
           options: <String>['--org', 'io.flutter.devicelab', '-t', 'module', 'hello'],
@@ -33,14 +34,14 @@ Future<Null> main() async {
 
       section('Add plugins');
 
-      final File pubspec = new File(path.join(directory.path, 'hello', 'pubspec.yaml'));
+      final File pubspec = new File(path.join(tempDir.path, 'hello', 'pubspec.yaml'));
       String content = await pubspec.readAsString();
       content = content.replaceFirst(
         '\ndependencies:\n',
         '\ndependencies:\n  battery:\n  package_info:\n',
       );
       await pubspec.writeAsString(content, flush: true);
-      await inDirectory(new Directory(path.join(directory.path, 'hello')), () async {
+      await inDirectory(new Directory(path.join(tempDir.path, 'hello')), () async {
         await flutter(
           'packages',
           options: <String>['get'],
@@ -49,7 +50,7 @@ Future<Null> main() async {
 
       section('Build Flutter module library archive');
 
-      await inDirectory(new Directory(path.join(directory.path, 'hello', '.android')), () async {
+      await inDirectory(new Directory(path.join(tempDir.path, 'hello', '.android')), () async {
         await exec(
           './gradlew',
           <String>['flutter:assembleDebug'],
@@ -58,7 +59,7 @@ Future<Null> main() async {
       });
 
       final bool aarBuilt = exists(new File(path.join(
-        directory.path,
+        tempDir.path,
         'hello',
         '.android',
         'Flutter',
@@ -74,7 +75,7 @@ Future<Null> main() async {
 
       section('Build ephemeral host app');
 
-      await inDirectory(new Directory(path.join(directory.path, 'hello')), () async {
+      await inDirectory(new Directory(path.join(tempDir.path, 'hello')), () async {
         await flutter(
           'build',
           options: <String>['apk'],
@@ -82,7 +83,7 @@ Future<Null> main() async {
       });
 
       final bool ephemeralHostApkBuilt = exists(new File(path.join(
-        directory.path,
+        tempDir.path,
         'hello',
         'build',
         'host',
@@ -98,13 +99,13 @@ Future<Null> main() async {
 
       section('Clean build');
 
-      await inDirectory(new Directory(path.join(directory.path, 'hello')), () async {
+      await inDirectory(new Directory(path.join(tempDir.path, 'hello')), () async {
         await flutter('clean');
       });
 
       section('Materialize host app');
 
-      await inDirectory(new Directory(path.join(directory.path, 'hello')), () async {
+      await inDirectory(new Directory(path.join(tempDir.path, 'hello')), () async {
         await flutter(
           'materialize',
           options: <String>['android'],
@@ -113,7 +114,7 @@ Future<Null> main() async {
 
       section('Build materialized host app');
 
-      await inDirectory(new Directory(path.join(directory.path, 'hello')), () async {
+      await inDirectory(new Directory(path.join(tempDir.path, 'hello')), () async {
         await flutter(
           'build',
           options: <String>['apk'],
@@ -121,7 +122,7 @@ Future<Null> main() async {
       });
 
       final bool materializedHostApkBuilt = exists(new File(path.join(
-        directory.path,
+        tempDir.path,
         'hello',
         'build',
         'host',
@@ -137,18 +138,18 @@ Future<Null> main() async {
 
       section('Add to Android app');
 
-      final Directory hostApp = new Directory(path.join(directory.path, 'hello_host_app'));
+      final Directory hostApp = new Directory(path.join(tempDir.path, 'hello_host_app'));
       mkdir(hostApp);
       recursiveCopy(
         new Directory(path.join(flutterDirectory.path, 'dev', 'integration_tests', 'android_host_app')),
         hostApp,
       );
       copy(
-        new File(path.join(directory.path, 'hello', '.android', 'gradlew')),
+        new File(path.join(tempDir.path, 'hello', '.android', 'gradlew')),
         hostApp,
       );
       copy(
-        new File(path.join(directory.path, 'hello', '.android', 'gradle', 'wrapper', 'gradle-wrapper.jar')),
+        new File(path.join(tempDir.path, 'hello', '.android', 'gradle', 'wrapper', 'gradle-wrapper.jar')),
         new Directory(path.join(hostApp.path, 'gradle', 'wrapper')),
       );
 
@@ -177,7 +178,7 @@ Future<Null> main() async {
     } catch (e) {
       return new TaskResult.failure(e.toString());
     } finally {
-      rmTree(directory);
+      rmTree(tempDir);
     }
   });
 }
diff --git a/dev/devicelab/lib/framework/utils.dart b/dev/devicelab/lib/framework/utils.dart
index 3263000b70..65b0923504 100644
--- a/dev/devicelab/lib/framework/utils.dart
+++ b/dev/devicelab/lib/framework/utils.dart
@@ -77,15 +77,23 @@ void fail(String message) {
   throw new BuildFailedError(message);
 }
 
-void rm(FileSystemEntity entity) {
-  if (entity.existsSync())
-    entity.deleteSync();
+// Remove the given file or directory.
+void rm(FileSystemEntity entity, { bool recursive = false}) {
+  if (entity.existsSync()) {
+    // This should not be necessary, but it turns out that
+    // on Windows it's common for deletions to fail due to
+    // bogus (we think) "access denied" errors.
+    try {
+      entity.deleteSync(recursive: recursive);
+    } on FileSystemException catch (error) {
+      print('Failed to delete ${entity.path}: $error');
+    }
+  }
 }
 
 /// Remove recursively.
 void rmTree(FileSystemEntity entity) {
-  if (entity.existsSync())
-    entity.deleteSync(recursive: true);
+  rm(entity, recursive: true);
 }
 
 List<FileSystemEntity> ls(Directory directory) => directory.listSync();
@@ -414,7 +422,7 @@ Future<Null> getFlutter(String revision) async {
   section('Get Flutter!');
 
   if (exists(flutterDirectory)) {
-    rmTree(flutterDirectory);
+    flutterDirectory.deleteSync(recursive: true);
   }
 
   await inDirectory(flutterDirectory.parent, () async {
diff --git a/dev/devicelab/lib/tasks/perf_tests.dart b/dev/devicelab/lib/tasks/perf_tests.dart
index 0d31ef63ff..cea0ca330f 100644
--- a/dev/devicelab/lib/tasks/perf_tests.dart
+++ b/dev/devicelab/lib/tasks/perf_tests.dart
@@ -73,8 +73,7 @@ TaskFunction createBasicMaterialCompileTest() {
     const String sampleAppName = 'sample_flutter_app';
     final Directory sampleDir = dir('${Directory.systemTemp.path}/$sampleAppName');
 
-    if (await sampleDir.exists())
-      rmTree(sampleDir);
+    rmTree(sampleDir);
 
     await inDirectory(Directory.systemTemp, () async {
       await flutter('create', options: <String>[sampleAppName]);
diff --git a/dev/devicelab/lib/tasks/plugin_tests.dart b/dev/devicelab/lib/tasks/plugin_tests.dart
index 3f032fa31e..556d99c756 100644
--- a/dev/devicelab/lib/tasks/plugin_tests.dart
+++ b/dev/devicelab/lib/tasks/plugin_tests.dart
@@ -33,23 +33,24 @@ class PluginTest {
 
   Future<TaskResult> call() async {
     section('Create Flutter project');
-    final Directory tmp = await Directory.systemTemp.createTemp('plugin');
-    final FlutterProject project = await FlutterProject.create(tmp, options);
-    if (buildTarget == 'ios') {
-      await prepareProvisioningCertificates(project.rootPath);
-    }
+    final Directory tempDir = Directory.systemTemp.createTempSync('flutter_devicelab_plugin_test.');
     try {
-      section('Add plugin');
-      await project.addPlugin('path_provider');
-
-      section('Build');
-      await project.build(buildTarget);
-
+      final FlutterProject project = await FlutterProject.create(tempDir, options);
+      try {
+        if (buildTarget == 'ios')
+          await prepareProvisioningCertificates(project.rootPath);
+        section('Add plugin');
+        await project.addPlugin('path_provider');
+        section('Build');
+        await project.build(buildTarget);
+      } finally {
+        await project.delete();
+      }
       return new TaskResult.success(null);
     } catch (e) {
       return new TaskResult.failure(e.toString());
     } finally {
-      await project.delete();
+      rmTree(tempDir);
     }
   }
 }
@@ -97,9 +98,9 @@ class FlutterProject {
         <String>['--stop'],
         canFail: true,
       );
-      // TODO(mravn): Investigating if flakiness is timing dependent.
+      // TODO(ianh): Investigating if flakiness is timing dependent.
       await new Future<Null>.delayed(const Duration(seconds: 10));
     }
-    await parent.delete(recursive: true);
+    rmTree(parent);
   }
 }
diff --git a/dev/tools/dartdoc.dart b/dev/tools/dartdoc.dart
index f672ef44aa..4ee08177aa 100644
--- a/dev/tools/dartdoc.dart
+++ b/dev/tools/dartdoc.dart
@@ -244,7 +244,7 @@ void createIndexAndCleanup() {
 void removeOldFlutterDocsDir() {
   try {
     new Directory('$kDocRoot/flutter').deleteSync(recursive: true);
-  } catch (e) {
+  } on FileSystemException {
     // If the directory does not exist, that's OK.
   }
 }
diff --git a/packages/flutter_driver/test/common.dart b/packages/flutter_driver/test/common.dart
index b36d043b0a..dbc658f949 100644
--- a/packages/flutter_driver/test/common.dart
+++ b/packages/flutter_driver/test/common.dart
@@ -2,13 +2,26 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:io';
+
 import 'package:test/test.dart' hide TypeMatcher, isInstanceOf;
 import 'package:test/test.dart' as test_package show TypeMatcher;
 
 export 'package:test/test.dart' hide TypeMatcher, isInstanceOf;
 
 // Defines a 'package:test' shim.
-// TODO(ianh): Remove this file once https://github.com/dart-lang/matcher/issues/98 is fixed
+// TODO(ianh): Clean this up once https://github.com/dart-lang/matcher/issues/98 is fixed
 
 /// A matcher that compares the type of the actual value to the type argument T.
 Matcher isInstanceOf<T>() => new test_package.TypeMatcher<T>(); // ignore: prefer_const_constructors, https://github.com/dart-lang/sdk/issues/32544
+
+void tryToDelete(Directory directory) {
+  // This should not be necessary, but it turns out that
+  // on Windows it's common for deletions to fail due to
+  // bogus (we think) "access denied" errors.
+  try {
+    directory.deleteSync(recursive: true);
+  } on FileSystemException catch (error) {
+    print('Failed to delete ${directory.path}: $error');
+  }
+}
\ No newline at end of file
diff --git a/packages/flutter_driver/test/src/timeline_summary_test.dart b/packages/flutter_driver/test/src/timeline_summary_test.dart
index 166fdbd425..96b38b184a 100644
--- a/packages/flutter_driver/test/src/timeline_summary_test.dart
+++ b/packages/flutter_driver/test/src/timeline_summary_test.dart
@@ -287,11 +287,11 @@ void main() {
 
       setUp(() {
         useMemoryFileSystemForTesting();
-        tempDir = fs.systemTempDirectory.createTempSync('flutter_driver_test');
+        tempDir = fs.systemTempDirectory.createTempSync('flutter_driver_test.');
       });
 
       tearDown(() {
-        tempDir.deleteSync(recursive: true);
+        tryToDelete(tempDir);
         restoreFileSystem();
       });
 
diff --git a/packages/flutter_tools/bin/fuchsia_tester.dart b/packages/flutter_tools/bin/fuchsia_tester.dart
index b77017d5e5..2182f6be3c 100644
--- a/packages/flutter_tools/bin/fuchsia_tester.dart
+++ b/packages/flutter_tools/bin/fuchsia_tester.dart
@@ -21,7 +21,7 @@ import 'package:flutter_tools/src/test/coverage_collector.dart';
 import 'package:flutter_tools/src/test/runner.dart';
 import 'package:flutter_tools/src/usage.dart';
 
-// Note: this was largely inspired by lib/src/commands/test.dart.
+// This was largely inspired by lib/src/commands/test.dart.
 
 const String _kOptionPackages = 'packages';
 const String _kOptionShell = 'shell';
@@ -71,10 +71,10 @@ Future<Null> run(List<String> args) async {
       .any((String option) => !argResults.options.contains(option))) {
     throwToolExit('Missing option! All options must be specified.');
   }
-  final Directory tempDirectory =
-      fs.systemTempDirectory.createTempSync('fuchsia_tester');
+  final Directory tempDir =
+      fs.systemTempDirectory.createTempSync('flutter_fuchsia_tester.');
   try {
-    Cache.flutterRoot = tempDirectory.path;
+    Cache.flutterRoot = tempDir.path;
     final Directory testDirectory =
         fs.directory(argResults[_kOptionTestDirectory]);
     final File testFile = fs.file(argResults[_kOptionTestFile]);
@@ -130,13 +130,13 @@ Future<Null> run(List<String> args) async {
       // collector expects currentDirectory to be the root of the dart
       // package (i.e. contains lib/ and test/ sub-dirs).
       fs.currentDirectory = testDirectory.parent;
-      if (!await
-          collector.collectCoverageData(argResults[_kOptionCoveragePath]))
+      if (!await collector.collectCoverageData(argResults[_kOptionCoveragePath]))
         throwToolExit('Failed to collect coverage data');
     }
   } finally {
-    tempDirectory.deleteSync(recursive: true);
+    tempDir.deleteSync(recursive: true);
   }
-  // Not sure why this is needed, but main() doesn't seem to exit on its own.
+  // TODO(ianh): There's apparently some sort of lost async task keeping the
+  // process open. Remove the next line once that's been resolved.
   exit(exitCode);
 }
diff --git a/packages/flutter_tools/lib/src/application_package.dart b/packages/flutter_tools/lib/src/application_package.dart
index ac7faf5d60..cbe569bb9b 100644
--- a/packages/flutter_tools/lib/src/application_package.dart
+++ b/packages/flutter_tools/lib/src/application_package.dart
@@ -175,8 +175,7 @@ abstract class IOSApp extends ApplicationPackage {
       bundleDir = fs.directory(applicationBinary);
     } else {
       // Try to unpack as an ipa.
-      final Directory tempDir = fs.systemTempDirectory.createTempSync(
-          'flutter_app_');
+      final Directory tempDir = fs.systemTempDirectory.createTempSync('flutter_app.');
       addShutdownHook(() async {
         await tempDir.delete(recursive: true);
       }, ShutdownStage.STILL_RECORDING);
diff --git a/packages/flutter_tools/lib/src/commands/update_packages.dart b/packages/flutter_tools/lib/src/commands/update_packages.dart
index 49f202e6a9..78e6a8c6b9 100644
--- a/packages/flutter_tools/lib/src/commands/update_packages.dart
+++ b/packages/flutter_tools/lib/src/commands/update_packages.dart
@@ -215,13 +215,13 @@ class UpdatePackagesCommand extends FlutterCommand {
       // pub tool will attempt to bring these dependencies up to the most recent
       // possible versions while honoring all their constraints.
       final PubDependencyTree tree = new PubDependencyTree(); // object to collect results
-      final Directory temporaryDirectory = fs.systemTempDirectory.createTempSync('flutter_update_packages_');
+      final Directory tempDir = fs.systemTempDirectory.createTempSync('flutter_update_packages.');
       try {
-        final File fakePackage = _pubspecFor(temporaryDirectory);
+        final File fakePackage = _pubspecFor(tempDir);
         fakePackage.createSync();
         fakePackage.writeAsStringSync(_generateFakePubspec(dependencies.values));
         // First we run "pub upgrade" on this generated package:
-        await pubGet(context: PubContext.updatePackages, directory: temporaryDirectory.path, upgrade: true, checkLastModified: false);
+        await pubGet(context: PubContext.updatePackages, directory: tempDir.path, upgrade: true, checkLastModified: false);
         // Then we run "pub deps --style=compact" on the result. We pipe all the
         // output to tree.fill(), which parses it so that it can create a graph
         // of all the dependencies so that we can figure out the transitive
@@ -230,12 +230,12 @@ class UpdatePackagesCommand extends FlutterCommand {
         await pub(
           <String>['deps', '--style=compact'],
           context: PubContext.updatePackages,
-          directory: temporaryDirectory.path,
+          directory: tempDir.path,
           filter: tree.fill,
           retry: false, // errors here are usually fatal since we're not hitting the network
         );
       } finally {
-        temporaryDirectory.deleteSync(recursive: true);
+        tempDir.deleteSync(recursive: true);
       }
 
       // The transitive dependency tree for the fake package does not contain
diff --git a/packages/flutter_tools/lib/src/ios/mac.dart b/packages/flutter_tools/lib/src/ios/mac.dart
index e8890f1495..f9a1e7aba2 100644
--- a/packages/flutter_tools/lib/src/ios/mac.dart
+++ b/packages/flutter_tools/lib/src/ios/mac.dart
@@ -318,13 +318,11 @@ Future<XcodeBuildResult> buildXcodeProject({
 
   Status buildSubStatus;
   Status initialBuildStatus;
-  Directory scriptOutputPipeTempDirectory;
+  Directory tempDir;
 
   if (logger.supportsColor) {
-    scriptOutputPipeTempDirectory = fs.systemTempDirectory
-        .createTempSync('flutter_build_log_pipe');
-    final File scriptOutputPipeFile =
-        scriptOutputPipeTempDirectory.childFile('pipe_to_stdout');
+    tempDir = fs.systemTempDirectory.createTempSync('flutter_build_log_pipe.');
+    final File scriptOutputPipeFile = tempDir.childFile('pipe_to_stdout');
     os.makePipe(scriptOutputPipeFile.path);
 
     Future<void> listenToScriptOutputLine() async {
@@ -362,7 +360,7 @@ Future<XcodeBuildResult> buildXcodeProject({
   initialBuildStatus?.cancel();
   buildStopwatch.stop();
   // Free pipe file.
-  scriptOutputPipeTempDirectory?.deleteSync(recursive: true);
+  tempDir?.deleteSync(recursive: true);
   printStatus(
     'Xcode build done.',
     ansiAlternative: 'Xcode build done.'.padRight(kDefaultStatusPadding + 1)
diff --git a/packages/flutter_tools/lib/src/runner/flutter_command_runner.dart b/packages/flutter_tools/lib/src/runner/flutter_command_runner.dart
index 5c665dfffd..454fac9843 100644
--- a/packages/flutter_tools/lib/src/runner/flutter_command_runner.dart
+++ b/packages/flutter_tools/lib/src/runner/flutter_command_runner.dart
@@ -233,13 +233,13 @@ class FlutterCommandRunner extends CommandRunner<Null> {
 
     if (topLevelResults['bug-report']) {
       // --bug-report implies --record-to=<tmp_path>
-      final Directory tmp = await const LocalFileSystem()
+      final Directory tempDir = const LocalFileSystem()
           .systemTempDirectory
-          .createTemp('flutter_tools_');
-      recordTo = tmp.path;
+          .createTempSync('flutter_tools_bug_report.');
+      recordTo = tempDir.path;
 
       // Record the arguments that were used to invoke this runner.
-      final File manifest = tmp.childFile('MANIFEST.txt');
+      final File manifest = tempDir.childFile('MANIFEST.txt');
       final StringBuffer buffer = new StringBuffer()
         ..writeln('# arguments')
         ..writeln(topLevelResults.arguments)
@@ -251,13 +251,14 @@ class FlutterCommandRunner extends CommandRunner<Null> {
       // ZIP the recording up once the recording has been serialized.
       addShutdownHook(() async {
         final File zipFile = getUniqueFile(fs.currentDirectory, 'bugreport', 'zip');
-        os.zip(tmp, zipFile);
+        os.zip(tempDir, zipFile);
         printStatus(
-            'Bug report written to ${zipFile.basename}.\n'
-            'Note that this bug report contains local paths, device '
-            'identifiers, and log snippets.');
+          'Bug report written to ${zipFile.basename}.\n'
+          'Note that this bug report contains local paths, device '
+          'identifiers, and log snippets.'
+        );
       }, ShutdownStage.POST_PROCESS_RECORDING);
-      addShutdownHook(() => tmp.delete(recursive: true), ShutdownStage.CLEANUP);
+      addShutdownHook(() => tempDir.delete(recursive: true), ShutdownStage.CLEANUP);
     }
 
     assert(recordTo == null || replayFrom == null);
diff --git a/packages/flutter_tools/lib/src/test/coverage_collector.dart b/packages/flutter_tools/lib/src/test/coverage_collector.dart
index 461038ca49..3ed1c9dcdd 100644
--- a/packages/flutter_tools/lib/src/test/coverage_collector.dart
+++ b/packages/flutter_tools/lib/src/test/coverage_collector.dart
@@ -136,7 +136,7 @@ class CoverageCollector extends TestWatcher {
         return false;
       }
 
-      final Directory tempDir = fs.systemTempDirectory.createTempSync('flutter_tools');
+      final Directory tempDir = fs.systemTempDirectory.createTempSync('flutter_tools_test_coverage.');
       try {
         final File sourceFile = coverageFile.copySync(fs.path.join(tempDir.path, 'lcov.source.info'));
         final ProcessResult result = processManager.runSync(<String>[
diff --git a/packages/flutter_tools/lib/src/test/flutter_platform.dart b/packages/flutter_tools/lib/src/test/flutter_platform.dart
index f219c08ea3..f5b56bb75f 100644
--- a/packages/flutter_tools/lib/src/test/flutter_platform.dart
+++ b/packages/flutter_tools/lib/src/test/flutter_platform.dart
@@ -203,7 +203,7 @@ class _Compiler {
     // Incremental compilation requests done for each test copy that file away
     // for independent execution.
     final Directory outputDillDirectory = fs.systemTempDirectory
-        .createTempSync('output_dill');
+        .createTempSync('flutter_test_compiler.');
     final File outputDill = outputDillDirectory.childFile('output.dill');
 
     bool suppressOutput = false;
@@ -656,15 +656,15 @@ class _FlutterPlatform extends PlatformPlugin {
   String _createListenerDart(List<_Finalizer> finalizers, int ourTestCount,
       String testPath, HttpServer server) {
     // Prepare a temporary directory to store the Dart file that will talk to us.
-    final Directory temporaryDirectory = fs.systemTempDirectory
-        .createTempSync('dart_test_listener');
+    final Directory tempDir = fs.systemTempDirectory
+        .createTempSync('flutter_test_listener.');
     finalizers.add(() async {
       printTrace('test $ourTestCount: deleting temporary directory');
-      temporaryDirectory.deleteSync(recursive: true);
+      tempDir.deleteSync(recursive: true);
     });
 
     // Prepare the Dart file that will talk to us and start the test.
-    final File listenerFile = fs.file('${temporaryDirectory.path}/listener.dart');
+    final File listenerFile = fs.file('${tempDir.path}/listener.dart');
     listenerFile.createSync();
     listenerFile.writeAsStringSync(_generateTestMain(
       testUrl: fs.path.toUri(fs.path.absolute(testPath)),
@@ -683,7 +683,7 @@ class _FlutterPlatform extends PlatformPlugin {
 
     // bundlePath needs to point to a folder with `platform.dill` file.
     final Directory tempBundleDirectory = fs.systemTempDirectory
-        .createTempSync('flutter_bundle_directory');
+        .createTempSync('flutter_test_bundle.');
     finalizers.add(() async {
       printTrace(
           'test $ourTestCount: deleting temporary bundle directory');
@@ -757,7 +757,7 @@ class _FlutterPlatform extends PlatformPlugin {
     sb.writeln('  <cachedir>/var/cache/fontconfig</cachedir>');
     sb.writeln('</fontconfig>');
 
-    final Directory fontsDir = fs.systemTempDirectory.createTempSync('flutter_fonts');
+    final Directory fontsDir = fs.systemTempDirectory.createTempSync('flutter_test_fonts.');
     _cachedFontConfig = fs.file('${fontsDir.path}/fonts.conf');
     _cachedFontConfig.createSync();
     _cachedFontConfig.writeAsStringSync(sb.toString());
diff --git a/packages/flutter_tools/test/analytics_test.dart b/packages/flutter_tools/test/analytics_test.dart
index b61cd35b02..f6f2b75945 100644
--- a/packages/flutter_tools/test/analytics_test.dart
+++ b/packages/flutter_tools/test/analytics_test.dart
@@ -21,7 +21,7 @@ import 'src/context.dart';
 
 void main() {
   group('analytics', () {
-    Directory temp;
+    Directory tempDir;
 
     setUpAll(() {
       Cache.disableLocking();
@@ -29,11 +29,11 @@ void main() {
 
     setUp(() {
       Cache.flutterRoot = '../..';
-      temp = fs.systemTempDirectory.createTempSync('flutter_tools');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_tools_analytics_test.');
     });
 
     tearDown(() {
-      temp.deleteSync(recursive: true);
+      tryToDelete(tempDir);
     });
 
     // Ensure we don't send anything when analytics is disabled.
@@ -42,11 +42,11 @@ void main() {
       flutterUsage.onSend.listen((Map<String, dynamic> data) => count++);
 
       flutterUsage.enabled = false;
-      await createProject(temp);
+      await createProject(tempDir);
       expect(count, 0);
 
       flutterUsage.enabled = true;
-      await createProject(temp);
+      await createProject(tempDir);
       expect(count, flutterUsage.isFirstRun ? 0 : 2);
 
       count = 0;
@@ -57,7 +57,7 @@ void main() {
       expect(count, 0);
     }, overrides: <Type, Generator>{
       FlutterVersion: () => new FlutterVersion(const Clock()),
-      Usage: () => new Usage(configDirOverride: temp.path),
+      Usage: () => new Usage(configDirOverride: tempDir.path),
     });
 
     // Ensure we don't send for the 'flutter config' command.
@@ -76,7 +76,7 @@ void main() {
       expect(count, 0);
     }, overrides: <Type, Generator>{
       FlutterVersion: () => new FlutterVersion(const Clock()),
-      Usage: () => new Usage(configDirOverride: temp.path),
+      Usage: () => new Usage(configDirOverride: tempDir.path),
     });
   });
 
@@ -151,9 +151,14 @@ void main() {
   });
 
   group('analytics bots', () {
-    Directory temp;
+    Directory tempDir;
+
     setUp(() {
-        temp = fs.systemTempDirectory.createTempSync('flutter_tools');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_tools_analytics_bots_test.');
+    });
+
+    tearDown(() {
+      tryToDelete(tempDir);
     });
 
     testUsingContext('don\'t send on bots', () async {
@@ -166,7 +171,7 @@ void main() {
       Usage: () => new Usage(
         settingsName: 'flutter_bot_test',
         versionOverride: 'dev/unknown',
-        configDirOverride: temp.path,
+        configDirOverride: tempDir.path,
       ),
     });
 
@@ -181,7 +186,7 @@ void main() {
       Usage: () => new Usage(
         settingsName: 'flutter_bot_test',
         versionOverride: 'dev/unknown',
-        configDirOverride: temp.path,
+        configDirOverride: tempDir.path,
       ),
     });
   });
diff --git a/packages/flutter_tools/test/android/android_sdk_test.dart b/packages/flutter_tools/test/android/android_sdk_test.dart
index 179db33277..870a0bf81b 100644
--- a/packages/flutter_tools/test/android/android_sdk_test.dart
+++ b/packages/flutter_tools/test/android/android_sdk_test.dart
@@ -30,8 +30,10 @@ void main() {
     Directory sdkDir;
 
     tearDown(() {
-      sdkDir?.deleteSync(recursive: true);
-      sdkDir = null;
+      if (sdkDir != null) {
+        tryToDelete(sdkDir);
+        sdkDir = null;
+      }
     });
 
     testUsingContext('parse sdk', () {
diff --git a/packages/flutter_tools/test/android/android_workflow_test.dart b/packages/flutter_tools/test/android/android_workflow_test.dart
index 48831650f3..70bc842e15 100644
--- a/packages/flutter_tools/test/android/android_workflow_test.dart
+++ b/packages/flutter_tools/test/android/android_workflow_test.dart
@@ -39,7 +39,6 @@ void main() {
 
   testUsingContext('licensesAccepted throws if cannot run sdkmanager', () async {
     processManager.succeed = false;
-    MockAndroidSdk.createSdkDirectory();
     when(sdk.sdkManagerPath).thenReturn('/foo/bar/sdkmanager');
     final AndroidWorkflow androidWorkflow = new AndroidWorkflow();
     expect(androidWorkflow.licensesAccepted, throwsToolExit());
@@ -52,7 +51,6 @@ void main() {
   });
 
   testUsingContext('licensesAccepted handles garbage/no output', () async {
-    MockAndroidSdk.createSdkDirectory();
     when(sdk.sdkManagerPath).thenReturn('/foo/bar/sdkmanager');
     final AndroidWorkflow androidWorkflow = new AndroidWorkflow();
     final LicensesAccepted result = await androidWorkflow.licensesAccepted;
@@ -68,7 +66,6 @@ void main() {
   });
 
   testUsingContext('licensesAccepted works for all licenses accepted', () async {
-    MockAndroidSdk.createSdkDirectory();
     when(sdk.sdkManagerPath).thenReturn('/foo/bar/sdkmanager');
     processManager.processFactory = processMetaFactory(<String>[
        '[=======================================] 100% Computing updates...             ',
@@ -87,7 +84,6 @@ void main() {
   });
 
   testUsingContext('licensesAccepted works for some licenses accepted', () async {
-    MockAndroidSdk.createSdkDirectory();
     when(sdk.sdkManagerPath).thenReturn('/foo/bar/sdkmanager');
     processManager.processFactory = processMetaFactory(<String>[
       '[=======================================] 100% Computing updates...             ',
@@ -107,7 +103,6 @@ void main() {
   });
 
   testUsingContext('licensesAccepted works for no licenses accepted', () async {
-    MockAndroidSdk.createSdkDirectory();
     when(sdk.sdkManagerPath).thenReturn('/foo/bar/sdkmanager');
     processManager.processFactory = processMetaFactory(<String>[
       '[=======================================] 100% Computing updates...             ',
@@ -127,7 +122,6 @@ void main() {
   });
 
   testUsingContext('runLicenseManager succeeds for version >= 26', () async {
-    MockAndroidSdk.createSdkDirectory();
     when(sdk.sdkManagerPath).thenReturn('/foo/bar/sdkmanager');
     when(sdk.sdkManagerVersion).thenReturn('26.0.0');
 
@@ -141,7 +135,6 @@ void main() {
   });
 
   testUsingContext('runLicenseManager errors for version < 26', () async {
-    MockAndroidSdk.createSdkDirectory();
     when(sdk.sdkManagerPath).thenReturn('/foo/bar/sdkmanager');
     when(sdk.sdkManagerVersion).thenReturn('25.0.0');
 
@@ -155,7 +148,6 @@ void main() {
   });
 
   testUsingContext('runLicenseManager errors correctly for null version', () async {
-    MockAndroidSdk.createSdkDirectory();
     when(sdk.sdkManagerPath).thenReturn('/foo/bar/sdkmanager');
     when(sdk.sdkManagerVersion).thenReturn(null);
 
@@ -169,7 +161,6 @@ void main() {
   });
 
   testUsingContext('runLicenseManager errors when sdkmanager is not found', () async {
-    MockAndroidSdk.createSdkDirectory();
     when(sdk.sdkManagerPath).thenReturn('/foo/bar/sdkmanager');
     processManager.succeed = false;
 
diff --git a/packages/flutter_tools/test/artifacts_test.dart b/packages/flutter_tools/test/artifacts_test.dart
index 7767736132..ac1c8fe776 100644
--- a/packages/flutter_tools/test/artifacts_test.dart
+++ b/packages/flutter_tools/test/artifacts_test.dart
@@ -18,12 +18,12 @@ void main() {
     CachedArtifacts artifacts;
 
     setUp(() {
-      tempDir = fs.systemTempDirectory.createTempSync('flutter_temp');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_tools_artifacts_test_cached.');
       artifacts = new CachedArtifacts();
     });
 
     tearDown(() {
-      tempDir.deleteSync(recursive: true);
+      tryToDelete(tempDir);
     });
 
     testUsingContext('getArtifactPath', () {
@@ -69,7 +69,7 @@ void main() {
     LocalEngineArtifacts artifacts;
 
     setUp(() {
-      tempDir = fs.systemTempDirectory.createTempSync('flutter_temp');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_tools_artifacts_test_local.');
       artifacts = new LocalEngineArtifacts(tempDir.path,
         fs.path.join(tempDir.path, 'out', 'android_debug_unopt'),
         fs.path.join(tempDir.path, 'out', 'host_debug_unopt'),
@@ -77,7 +77,7 @@ void main() {
     });
 
     tearDown(() {
-      tempDir.deleteSync(recursive: true);
+      tryToDelete(tempDir);
     });
 
     testUsingContext('getArtifactPath', () {
diff --git a/packages/flutter_tools/test/asset_bundle_package_fonts_test.dart b/packages/flutter_tools/test/asset_bundle_package_fonts_test.dart
index dc7c135eb1..4804dba56e 100644
--- a/packages/flutter_tools/test/asset_bundle_package_fonts_test.dart
+++ b/packages/flutter_tools/test/asset_bundle_package_fonts_test.dart
@@ -95,20 +95,14 @@ $fontsSection
   Directory oldCurrentDir;
 
   setUp(() async {
-    tempDir = await fs.systemTempDirectory.createTemp('asset_bundle_tests');
+    tempDir = fs.systemTempDirectory.createTempSync('flutter_asset_bundle_test.');
     oldCurrentDir = fs.currentDirectory;
     fs.currentDirectory = tempDir;
   });
 
   tearDown(() {
     fs.currentDirectory = oldCurrentDir;
-    try {
-      tempDir?.deleteSync(recursive: true);
-      tempDir = null;
-    } on FileSystemException catch (e) {
-      // Do nothing, windows sometimes has trouble deleting.
-      print('Ignored exception during tearDown: $e');
-    }
+    tryToDelete(tempDir);
   });
 
   group('AssetBundle fonts from packages', () {
diff --git a/packages/flutter_tools/test/asset_bundle_package_test.dart b/packages/flutter_tools/test/asset_bundle_package_test.dart
index 624607698a..4361bba3ba 100644
--- a/packages/flutter_tools/test/asset_bundle_package_test.dart
+++ b/packages/flutter_tools/test/asset_bundle_package_test.dart
@@ -106,20 +106,14 @@ $assetsSection
   Directory oldCurrentDir;
 
   setUp(() async {
-    tempDir = await fs.systemTempDirectory.createTemp('asset_bundle_tests');
+    tempDir = fs.systemTempDirectory.createTempSync('flutter_asset_bundle_test.');
     oldCurrentDir = fs.currentDirectory;
     fs.currentDirectory = tempDir;
   });
 
   tearDown(() {
     fs.currentDirectory = oldCurrentDir;
-    try {
-      tempDir?.deleteSync(recursive: true);
-      tempDir = null;
-    } on FileSystemException catch (e) {
-      // Do nothing, windows sometimes has trouble deleting.
-      print('Ignored exception during tearDown: $e');
-    }
+    tryToDelete(tempDir);
   });
 
   group('AssetBundle assets from packages', () {
diff --git a/packages/flutter_tools/test/asset_bundle_test.dart b/packages/flutter_tools/test/asset_bundle_test.dart
index e4fdf8ee18..afafc7171c 100644
--- a/packages/flutter_tools/test/asset_bundle_test.dart
+++ b/packages/flutter_tools/test/asset_bundle_test.dart
@@ -25,20 +25,14 @@ void main() {
     Directory oldCurrentDir;
 
     setUp(() async {
-      tempDir = await fs.systemTempDirectory.createTemp('asset_bundle_tests');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_asset_bundle_test.');
       oldCurrentDir = fs.currentDirectory;
       fs.currentDirectory = tempDir;
     });
 
     tearDown(() {
       fs.currentDirectory = oldCurrentDir;
-      try {
-        tempDir?.deleteSync(recursive: true);
-        tempDir = null;
-      } on FileSystemException catch (e) {
-        // Do nothing, windows sometimes has trouble deleting.
-        print('Ignored exception during tearDown: $e');
-      }
+      tryToDelete(tempDir);
     });
 
     testUsingContext('nonempty', () async {
diff --git a/packages/flutter_tools/test/asset_bundle_variant_test.dart b/packages/flutter_tools/test/asset_bundle_variant_test.dart
index e58f0e7f0d..afdbcc6a90 100644
--- a/packages/flutter_tools/test/asset_bundle_variant_test.dart
+++ b/packages/flutter_tools/test/asset_bundle_variant_test.dart
@@ -20,20 +20,14 @@ void main() {
   Directory oldCurrentDir;
 
   setUp(() async {
-    tempDir = await fs.systemTempDirectory.createTemp('asset_bundle_tests');
+    tempDir = fs.systemTempDirectory.createTempSync('flutter_asset_bundle_variant_test.');
     oldCurrentDir = fs.currentDirectory;
     fs.currentDirectory = tempDir;
   });
 
   tearDown(() {
     fs.currentDirectory = oldCurrentDir;
-    try {
-      tempDir?.deleteSync(recursive: true);
-      tempDir = null;
-    } on FileSystemException catch (e) {
-      // Do nothing, windows sometimes has trouble deleting.
-      print('Ignored exception during tearDown: $e');
-    }
+    tryToDelete(tempDir);
   });
 
   group('AssetBundle asset variants', () {
diff --git a/packages/flutter_tools/test/base/os_utils_test.dart b/packages/flutter_tools/test/base/os_utils_test.dart
index 5f6987c26b..27c9849707 100644
--- a/packages/flutter_tools/test/base/os_utils_test.dart
+++ b/packages/flutter_tools/test/base/os_utils_test.dart
@@ -11,18 +11,18 @@ import '../src/context.dart';
 
 void main() {
   group('OperatingSystemUtils', () {
-    Directory temp;
+    Directory tempDir;
 
     setUp(() {
-      temp = fs.systemTempDirectory.createTempSync('flutter_tools');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_tools_os_utils_test.');
     });
 
     tearDown(() {
-      temp.deleteSync(recursive: true);
+      tryToDelete(tempDir);
     });
 
     testUsingContext('makeExecutable', () async {
-      final File file = fs.file(fs.path.join(temp.path, 'foo.script'));
+      final File file = fs.file(fs.path.join(tempDir.path, 'foo.script'));
       file.writeAsStringSync('hello world');
       os.makeExecutable(file);
 
diff --git a/packages/flutter_tools/test/commands/analyze_continuously_test.dart b/packages/flutter_tools/test/commands/analyze_continuously_test.dart
index dfb1972edf..018dc85595 100644
--- a/packages/flutter_tools/test/commands/analyze_continuously_test.dart
+++ b/packages/flutter_tools/test/commands/analyze_continuously_test.dart
@@ -20,11 +20,11 @@ void main() {
 
   setUp(() {
     FlutterCommandRunner.initFlutterRoot();
-    tempDir = fs.systemTempDirectory.createTempSync('analysis_test');
+    tempDir = fs.systemTempDirectory.createTempSync('flutter_analysis_test.');
   });
 
   tearDown(() {
-    tempDir?.deleteSync(recursive: true);
+    tryToDelete(tempDir);
     return server?.dispose();
   });
 
diff --git a/packages/flutter_tools/test/commands/analyze_once_test.dart b/packages/flutter_tools/test/commands/analyze_once_test.dart
index 37360820ba..3b0ee80b4a 100644
--- a/packages/flutter_tools/test/commands/analyze_once_test.dart
+++ b/packages/flutter_tools/test/commands/analyze_once_test.dart
@@ -28,18 +28,13 @@ void main() {
 
     setUpAll(() {
       Cache.disableLocking();
-      tempDir = fs.systemTempDirectory.createTempSync('analyze_once_test_').absolute;
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_analyze_once_test_1.').absolute;
       projectPath = fs.path.join(tempDir.path, 'flutter_project');
       libMain = fs.file(fs.path.join(projectPath, 'lib', 'main.dart'));
     });
 
     tearDownAll(() {
-      try {
-        tempDir?.deleteSync(recursive: true);
-      } on FileSystemException catch (e) {
-        // ignore errors deleting the temporary directory
-        print('Ignored exception during tearDown: $e');
-      }
+      tryToDelete(tempDir);
     });
 
     // Create a project to be analyzed
@@ -134,7 +129,7 @@ void main() {
     }, timeout: allowForSlowAnalyzeTests);
 
     testUsingContext('no duplicate issues', () async {
-      final Directory tempDir = fs.systemTempDirectory.createTempSync('analyze_once_test_').absolute;
+      final Directory tempDir = fs.systemTempDirectory.createTempSync('flutter_analyze_once_test_2.').absolute;
 
       try {
         final File foo = fs.file(fs.path.join(tempDir.path, 'foo.dart'));
@@ -163,7 +158,7 @@ void bar() {
           toolExit: true,
         );
       } finally {
-        tempDir.deleteSync(recursive: true);
+        tryToDelete(tempDir);
       }
     });
 
@@ -171,7 +166,7 @@ void bar() {
       const String contents = '''
 StringBuffer bar = StringBuffer('baz');
 ''';
-      final Directory tempDir = fs.systemTempDirectory.createTempSync();
+      final Directory tempDir = fs.systemTempDirectory.createTempSync('flutter_analyze_once_test_3.');
       tempDir.childFile('main.dart').writeAsStringSync(contents);
       try {
         await runCommand(
@@ -180,7 +175,7 @@ StringBuffer bar = StringBuffer('baz');
           statusTextContains: <String>['No issues found!'],
         );
       } finally {
-        tempDir.deleteSync(recursive: true);
+        tryToDelete(tempDir);
       }
     });
   });
diff --git a/packages/flutter_tools/test/commands/analyze_test.dart b/packages/flutter_tools/test/commands/analyze_test.dart
index bae562c6ea..d86b5745c6 100644
--- a/packages/flutter_tools/test/commands/analyze_test.dart
+++ b/packages/flutter_tools/test/commands/analyze_test.dart
@@ -20,7 +20,11 @@ void main() {
     fs = new MemoryFileSystem();
     fs.directory(_kFlutterRoot).createSync(recursive: true);
     Cache.flutterRoot = _kFlutterRoot;
-    tempDir = fs.systemTempDirectory.createTempSync('analysis_test');
+    tempDir = fs.systemTempDirectory.createTempSync('flutter_analysis_test.');
+  });
+
+  tearDown(() {
+    tryToDelete(tempDir);
   });
 
   group('analyze', () {
diff --git a/packages/flutter_tools/test/commands/create_test.dart b/packages/flutter_tools/test/commands/create_test.dart
index d71d4fbd75..18edccef06 100644
--- a/packages/flutter_tools/test/commands/create_test.dart
+++ b/packages/flutter_tools/test/commands/create_test.dart
@@ -24,7 +24,7 @@ const String frameworkChannel = 'omega';
 
 void main() {
   group('create', () {
-    Directory temp;
+    Directory tempDir;
     Directory projectDir;
     FlutterVersion mockFlutterVersion;
     LoggingProcessManager loggingProcessManager;
@@ -35,18 +35,13 @@ void main() {
 
     setUp(() {
       loggingProcessManager = new LoggingProcessManager();
-      temp = fs.systemTempDirectory.createTempSync('flutter_tools');
-      projectDir = temp.childDirectory('flutter_project');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_tools_create_test.');
+      projectDir = tempDir.childDirectory('flutter_project');
       mockFlutterVersion = new MockFlutterVersion();
     });
 
     tearDown(() {
-      try {
-        temp.deleteSync(recursive: true);
-      } on FileSystemException catch (e) {
-        // ignore errors deleting the temporary directory
-        print('Ignored exception during tearDown: $e');
-      }
+      tryToDelete(tempDir);
     });
 
     // Verify that we create a project that is well-formed.
diff --git a/packages/flutter_tools/test/commands/drive_test.dart b/packages/flutter_tools/test/commands/drive_test.dart
index 9507805d2a..c15bbc9591 100644
--- a/packages/flutter_tools/test/commands/drive_test.dart
+++ b/packages/flutter_tools/test/commands/drive_test.dart
@@ -24,7 +24,7 @@ void main() {
     DriveCommand command;
     Device mockDevice;
     MemoryFileSystem fs;
-    Directory cwd;
+    Directory tempDir;
 
     void withMockDevice([Device mock]) {
       mockDevice = mock ?? new MockDevice();
@@ -40,8 +40,8 @@ void main() {
       command = new DriveCommand();
       applyMocksToCommand(command);
       fs = new MemoryFileSystem();
-      cwd = fs.systemTempDirectory.createTempSync('some_app_');
-      fs.currentDirectory = cwd;
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_drive_test.');
+      fs.currentDirectory = tempDir;
       fs.directory('test').createSync();
       fs.directory('test_driver').createSync();
       fs.file('pubspec.yaml')..createSync();
@@ -68,13 +68,14 @@ void main() {
       restoreAppStopper();
       restoreTestRunner();
       restoreTargetDeviceFinder();
+      tryToDelete(tempDir);
     });
 
     testUsingContext('returns 1 when test file is not found', () async {
       withMockDevice();
 
-      final String testApp = fs.path.join(cwd.path, 'test', 'e2e.dart');
-      final String testFile = fs.path.join(cwd.path, 'test_driver', 'e2e_test.dart');
+      final String testApp = fs.path.join(tempDir.path, 'test', 'e2e.dart');
+      final String testFile = fs.path.join(tempDir.path, 'test_driver', 'e2e_test.dart');
       fs.file(testApp).createSync(recursive: true);
 
       final List<String> args = <String>[
@@ -96,8 +97,8 @@ void main() {
       withMockDevice();
       appStarter = expectAsync1((DriveCommand command) async => null);
 
-      final String testApp = fs.path.join(cwd.path, 'test_driver', 'e2e.dart');
-      final String testFile = fs.path.join(cwd.path, 'test_driver', 'e2e_test.dart');
+      final String testApp = fs.path.join(tempDir.path, 'test_driver', 'e2e.dart');
+      final String testFile = fs.path.join(tempDir.path, 'test_driver', 'e2e_test.dart');
 
       final MemoryFileSystem memFs = fs;
       await memFs.file(testApp).writeAsString('main() { }');
@@ -119,7 +120,7 @@ void main() {
     });
 
     testUsingContext('returns 1 when app file is outside package', () async {
-      final String appFile = fs.path.join(cwd.dirname, 'other_app', 'app.dart');
+      final String appFile = fs.path.join(tempDir.dirname, 'other_app', 'app.dart');
       fs.file(appFile).createSync(recursive: true);
       final List<String> args = <String>[
         'drive',
@@ -131,7 +132,7 @@ void main() {
       } on ToolExit catch (e) {
         expect(e.exitCode ?? 1, 1);
         expect(testLogger.errorText, contains(
-            'Application file $appFile is outside the package directory ${cwd.path}',
+            'Application file $appFile is outside the package directory ${tempDir.path}',
         ));
       }
     }, overrides: <Type, Generator>{
@@ -139,7 +140,7 @@ void main() {
     });
 
     testUsingContext('returns 1 when app file is in the root dir', () async {
-      final String appFile = fs.path.join(cwd.path, 'main.dart');
+      final String appFile = fs.path.join(tempDir.path, 'main.dart');
       fs.file(appFile).createSync(recursive: true);
       final List<String> args = <String>[
         'drive',
@@ -162,8 +163,8 @@ void main() {
     testUsingContext('returns 0 when test ends successfully', () async {
       withMockDevice();
 
-      final String testApp = fs.path.join(cwd.path, 'test', 'e2e.dart');
-      final String testFile = fs.path.join(cwd.path, 'test_driver', 'e2e_test.dart');
+      final String testApp = fs.path.join(tempDir.path, 'test', 'e2e.dart');
+      final String testFile = fs.path.join(tempDir.path, 'test_driver', 'e2e_test.dart');
 
       appStarter = expectAsync1((DriveCommand command) async {
         return new LaunchResult.succeeded();
@@ -193,8 +194,8 @@ void main() {
     testUsingContext('returns exitCode set by test runner', () async {
       withMockDevice();
 
-      final String testApp = fs.path.join(cwd.path, 'test', 'e2e.dart');
-      final String testFile = fs.path.join(cwd.path, 'test_driver', 'e2e_test.dart');
+      final String testApp = fs.path.join(tempDir.path, 'test', 'e2e.dart');
+      final String testFile = fs.path.join(tempDir.path, 'test_driver', 'e2e_test.dart');
 
       appStarter = expectAsync1((DriveCommand command) async {
         return new LaunchResult.succeeded();
diff --git a/packages/flutter_tools/test/commands/format_test.dart b/packages/flutter_tools/test/commands/format_test.dart
index 43e7b5cecb..752e720da1 100644
--- a/packages/flutter_tools/test/commands/format_test.dart
+++ b/packages/flutter_tools/test/commands/format_test.dart
@@ -12,19 +12,19 @@ import '../src/context.dart';
 
 void main() {
   group('format', () {
-    Directory temp;
+    Directory tempDir;
 
     setUp(() {
       Cache.disableLocking();
-      temp = fs.systemTempDirectory.createTempSync('flutter_tools');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_tools_format_test.');
     });
 
     tearDown(() {
-      temp.deleteSync(recursive: true);
+      tryToDelete(tempDir);
     });
 
     testUsingContext('a file', () async {
-      final String projectPath = await createProject(temp);
+      final String projectPath = await createProject(tempDir);
 
       final File srcFile = fs.file(fs.path.join(projectPath, 'lib', 'main.dart'));
       final String original = srcFile.readAsStringSync();
@@ -39,7 +39,7 @@ void main() {
     });
 
     testUsingContext('dry-run', () async {
-      final String projectPath = await createProject(temp);
+      final String projectPath = await createProject(tempDir);
 
       final File srcFile = fs.file(
           fs.path.join(projectPath, 'lib', 'main.dart'));
@@ -56,7 +56,7 @@ void main() {
     });
 
     testUsingContext('dry-run with set-exit-if-changed', () async {
-      final String projectPath = await createProject(temp);
+      final String projectPath = await createProject(tempDir);
 
       final File srcFile = fs.file(
           fs.path.join(projectPath, 'lib', 'main.dart'));
diff --git a/packages/flutter_tools/test/commands/ide_config_test.dart b/packages/flutter_tools/test/commands/ide_config_test.dart
index aa97518fa1..79e799f952 100644
--- a/packages/flutter_tools/test/commands/ide_config_test.dart
+++ b/packages/flutter_tools/test/commands/ide_config_test.dart
@@ -15,15 +15,15 @@ import '../src/context.dart';
 
 void main() {
   group('ide_config', () {
-    Directory temp;
+    Directory tempDir;
     Directory templateDir;
     Directory intellijDir;
     Directory toolsDir;
 
     Map<String, String> _getFilesystemContents([Directory root]) {
-      final String tempPath = temp.absolute.path;
+      final String tempPath = tempDir.absolute.path;
       final List<String> paths =
-          (root ?? temp).listSync(recursive: true).map((FileSystemEntity entity) {
+          (root ?? tempDir).listSync(recursive: true).map((FileSystemEntity entity) {
         final String relativePath = fs.path.relative(entity.path, from: tempPath);
         return relativePath;
       }).toList();
@@ -40,7 +40,7 @@ void main() {
     }
 
     Map<String, String> _getManifest(Directory base, String marker, {bool isTemplate = false}) {
-      final String basePath = fs.path.relative(base.path, from: temp.absolute.path);
+      final String basePath = fs.path.relative(base.path, from: tempDir.absolute.path);
       final String suffix = isTemplate ? Template.copyTemplateExtension : '';
       return <String, String>{
         fs.path.join(basePath, '.idea'): 'dir',
@@ -59,12 +59,12 @@ void main() {
     void _populateDir(Map<String, String> manifest) {
       for (String key in manifest.keys) {
         if (manifest[key] == 'dir') {
-          temp.childDirectory(key)..createSync(recursive: true);
+          tempDir.childDirectory(key)..createSync(recursive: true);
         }
       }
       for (String key in manifest.keys) {
         if (manifest[key] != 'dir') {
-          temp.childFile(key)
+          tempDir.childFile(key)
             ..createSync(recursive: true)
             ..writeAsStringSync(manifest[key]);
         }
@@ -72,7 +72,7 @@ void main() {
     }
 
     bool _fileOrDirectoryExists(String path) {
-      final String absPath = fs.path.join(temp.absolute.path, path);
+      final String absPath = fs.path.join(tempDir.absolute.path, path);
       return fs.file(absPath).existsSync() || fs.directory(absPath).existsSync();
     }
 
@@ -82,15 +82,15 @@ void main() {
       Map<String, String> expectedContents = const <String, String>{},
       List<String> unexpectedPaths = const <String>[],
     }) async {
-      dir ??= temp;
+      dir ??= tempDir;
       final IdeConfigCommand command = new IdeConfigCommand();
       final CommandRunner<Null> runner = createTestCommandRunner(command);
-      final List<String> finalArgs = <String>['--flutter-root=${temp.absolute.path}', 'ide-config'];
+      final List<String> finalArgs = <String>['--flutter-root=${tempDir.absolute.path}', 'ide-config'];
       finalArgs.addAll(args);
       await runner.run(finalArgs);
 
       for (String path in expectedContents.keys) {
-        final String absPath = fs.path.join(temp.absolute.path, path);
+        final String absPath = fs.path.join(tempDir.absolute.path, path);
         expect(_fileOrDirectoryExists(fs.path.join(dir.path, path)), true,
             reason: "$path doesn't exist");
         if (fs.file(absPath).existsSync()) {
@@ -108,15 +108,15 @@ void main() {
     });
 
     setUp(() {
-      temp = fs.systemTempDirectory.createTempSync('flutter_tools_');
-      final Directory packagesDir = temp.childDirectory('packages')..createSync(recursive: true);
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_tools_ide_config_test.');
+      final Directory packagesDir = tempDir.childDirectory('packages')..createSync(recursive: true);
       toolsDir = packagesDir.childDirectory('flutter_tools')..createSync();
       templateDir = toolsDir.childDirectory('ide_templates')..createSync();
       intellijDir = templateDir.childDirectory('intellij')..createSync();
     });
 
     tearDown(() {
-      temp.deleteSync(recursive: true);
+      tryToDelete(tempDir);
     });
 
     testUsingContext("doesn't touch existing files without --overwrite", () async {
@@ -126,7 +126,7 @@ void main() {
         isTemplate: true,
       );
       final Map<String, String> flutterManifest = _getManifest(
-        temp,
+        tempDir,
         'existing',
       );
       _populateDir(templateManifest);
@@ -144,7 +144,7 @@ void main() {
         isTemplate: true,
       );
       final Map<String, String> flutterManifest = _getManifest(
-        temp,
+        tempDir,
         'template',
       );
       _populateDir(templateManifest);
@@ -162,13 +162,13 @@ void main() {
         isTemplate: true,
       );
       final Map<String, String> flutterManifest = _getManifest(
-        temp,
+        tempDir,
         'existing',
       );
       _populateDir(templateManifest);
       _populateDir(flutterManifest);
       final Map<String, String> overwrittenManifest = _getManifest(
-        temp,
+        tempDir,
         'template',
       );
       final Map<String, String> expectedContents = templateManifest;
@@ -196,7 +196,7 @@ void main() {
       _populateDir(templateManifest);
       templateManifest[flutterIml] = 'flutter existing';
       final Map<String, String> flutterManifest = _getManifest(
-        temp,
+        tempDir,
         'existing',
       );
       _populateDir(flutterManifest);
@@ -216,7 +216,7 @@ void main() {
       );
       _populateDir(templateManifest);
       final Map<String, String> flutterManifest = _getManifest(
-        temp,
+        tempDir,
         'existing',
       );
       _populateDir(flutterManifest);
@@ -241,7 +241,7 @@ void main() {
       );
       _populateDir(templateManifest);
       final Map<String, String> flutterManifest = _getManifest(
-        temp,
+        tempDir,
         'existing',
       );
       flutterManifest.remove('flutter.iml');
@@ -275,7 +275,7 @@ void main() {
       );
       _populateDir(templateManifest);
       final Map<String, String> flutterManifest = _getManifest(
-        temp,
+        tempDir,
         'existing',
       );
       flutterManifest.remove(fs.path.join('packages', 'new', 'deep.iml'));
diff --git a/packages/flutter_tools/test/commands/packages_test.dart b/packages/flutter_tools/test/commands/packages_test.dart
index 7d5d67025b..efa71ddabf 100644
--- a/packages/flutter_tools/test/commands/packages_test.dart
+++ b/packages/flutter_tools/test/commands/packages_test.dart
@@ -35,18 +35,18 @@ class AlwaysFalseBotDetector implements BotDetector {
 void main() {
   Cache.disableLocking();
   group('packages get/upgrade', () {
-    Directory temp;
+    Directory tempDir;
 
     setUp(() {
-      temp = fs.systemTempDirectory.createTempSync('flutter_tools');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_tools_packages_test.');
     });
 
     tearDown(() {
-      temp.deleteSync(recursive: true);
+      tryToDelete(tempDir);
     });
 
     Future<String> createProjectWithPlugin(String plugin) async {
-      final String projectPath = await createProject(temp);
+      final String projectPath = await createProject(tempDir);
       final File pubspec = fs.file(fs.path.join(projectPath, 'pubspec.yaml'));
       String content = await pubspec.readAsString();
       content = content.replaceFirst(
@@ -168,7 +168,7 @@ void main() {
     }
 
     testUsingContext('get fetches packages', () async {
-      final String projectPath = await createProject(temp);
+      final String projectPath = await createProject(tempDir);
       removeGeneratedFiles(projectPath);
 
       await runCommandIn(projectPath, 'get');
@@ -178,7 +178,7 @@ void main() {
     }, timeout: allowForRemotePubInvocation);
 
     testUsingContext('get --offline fetches packages', () async {
-      final String projectPath = await createProject(temp);
+      final String projectPath = await createProject(tempDir);
       removeGeneratedFiles(projectPath);
 
       await runCommandIn(projectPath, 'get', args: <String>['--offline']);
@@ -188,7 +188,7 @@ void main() {
     }, timeout: allowForCreateFlutterProject);
 
     testUsingContext('upgrade fetches packages', () async {
-      final String projectPath = await createProject(temp);
+      final String projectPath = await createProject(tempDir);
       removeGeneratedFiles(projectPath);
 
       await runCommandIn(projectPath, 'upgrade');
@@ -210,7 +210,7 @@ void main() {
     }, timeout: allowForRemotePubInvocation, skip: true);
     testUsingContext('get fetches packages and injects plugin in plugin project', () async {
       final String projectPath = await createProject(
-        temp,
+        tempDir,
         arguments: <String>['-t', 'plugin', '--no-pub'],
       );
       final String exampleProjectPath = fs.path.join(projectPath, 'example');
diff --git a/packages/flutter_tools/test/commands/upgrade_test.dart b/packages/flutter_tools/test/commands/upgrade_test.dart
index 16469bebed..f4a0f0da80 100644
--- a/packages/flutter_tools/test/commands/upgrade_test.dart
+++ b/packages/flutter_tools/test/commands/upgrade_test.dart
@@ -35,18 +35,18 @@ void main() {
     });
 
     group('findProjectRoot', () {
-      Directory temp;
+      Directory tempDir;
 
       setUp(() async {
-        temp = fs.systemTempDirectory.createTempSync('flutter_tools');
+        tempDir = fs.systemTempDirectory.createTempSync('flutter_tools_upgrade_test.');
       });
 
       tearDown(() {
-        temp.deleteSync(recursive: true);
+        tryToDelete(tempDir);
       });
 
       testUsingContext('in project', () async {
-        final String projectPath = await createProject(temp);
+        final String projectPath = await createProject(tempDir);
         expect(findProjectRoot(projectPath), projectPath);
         expect(findProjectRoot(fs.path.join(projectPath, 'lib')), projectPath);
 
@@ -56,7 +56,7 @@ void main() {
       });
 
       testUsingContext('outside project', () async {
-        final String projectPath = await createProject(temp);
+        final String projectPath = await createProject(tempDir);
         expect(findProjectRoot(fs.directory(projectPath).parent.path), null);
         expect(findProjectRoot(Cache.flutterRoot), null);
       });
diff --git a/packages/flutter_tools/test/config_test.dart b/packages/flutter_tools/test/config_test.dart
index e476cb8f41..30edb71d5d 100644
--- a/packages/flutter_tools/test/config_test.dart
+++ b/packages/flutter_tools/test/config_test.dart
@@ -9,13 +9,18 @@ import 'src/common.dart';
 
 void main() {
   Config config;
+  Directory tempDir;
 
   setUp(() {
-    final Directory tempDirectory = fs.systemTempDirectory.createTempSync('flutter_test');
-    final File file = fs.file(fs.path.join(tempDirectory.path, '.settings'));
+    tempDir = fs.systemTempDirectory.createTempSync('flutter_config_test.');
+    final File file = fs.file(fs.path.join(tempDir.path, '.settings'));
     config = new Config(file);
   });
 
+  tearDown(() {
+    tryToDelete(tempDir);
+  });
+
   group('config', () {
     test('get set value', () async {
       expect(config.getValue('foo'), null);
diff --git a/packages/flutter_tools/test/dependency_checker_test.dart b/packages/flutter_tools/test/dependency_checker_test.dart
index 0c55782256..1fdbc7c992 100644
--- a/packages/flutter_tools/test/dependency_checker_test.dart
+++ b/packages/flutter_tools/test/dependency_checker_test.dart
@@ -93,16 +93,18 @@ void main() {
     /// Tests that the flutter tool doesn't crash and displays a warning when its own location
     /// changed since it was last referenced to in a package's .packages file.
     testUsingContext('moved flutter sdk', () async {
-      final Directory destinationPath = fs.systemTempDirectory.createTempSync('dependency_checker_test_');
+      final Directory tempDir = fs.systemTempDirectory.createTempSync('flutter_dependency_checker_test.');
+
       // Copy the golden input and let the test run in an isolated temporary in-memory file system.
       const LocalFileSystem localFileSystem = LocalFileSystem();
       final Directory sourcePath = localFileSystem.directory(localFileSystem.path.join(dataPath, 'changed_sdk_location'));
-      copyDirectorySync(sourcePath, destinationPath);
-      fs.currentDirectory = destinationPath;
+      copyDirectorySync(sourcePath, tempDir);
+      fs.currentDirectory = tempDir;
 
       // Doesn't matter what commands we run. Arbitrarily list devices here.
       await createTestCommandRunner(new DevicesCommand()).run(<String>['devices']);
       expect(testLogger.errorText, contains('.packages'));
+      tryToDelete(tempDir);
     }, overrides: <Type, Generator>{
       FileSystem: () => testFileSystem,
     });
diff --git a/packages/flutter_tools/test/devfs_test.dart b/packages/flutter_tools/test/devfs_test.dart
index b2fb44532d..6a9d309b92 100644
--- a/packages/flutter_tools/test/devfs_test.dart
+++ b/packages/flutter_tools/test/devfs_test.dart
@@ -459,15 +459,14 @@ final List<Directory> _tempDirs = <Directory>[];
 final Map <String, Uri> _packages = <String, Uri>{};
 
 Directory _newTempDir(FileSystem fs) {
-  final Directory tempDir = fs.systemTempDirectory.createTempSync('devfs${_tempDirs.length}');
+  final Directory tempDir = fs.systemTempDirectory.createTempSync('flutter_devfs${_tempDirs.length}_test.');
   _tempDirs.add(tempDir);
   return tempDir;
 }
 
 void _cleanupTempDirs() {
-  while (_tempDirs.isNotEmpty) {
-    _tempDirs.removeLast().deleteSync(recursive: true);
-  }
+  while (_tempDirs.isNotEmpty)
+    tryToDelete(_tempDirs.removeLast());
 }
 
 Future<Null> _createPackage(FileSystem fs, String pkgName, String pkgFileName, { bool doubleSlash = false }) async {
diff --git a/packages/flutter_tools/test/integration/expression_evaluation_test.dart b/packages/flutter_tools/test/integration/expression_evaluation_test.dart
index 677bd29d80..e68b7c2486 100644
--- a/packages/flutter_tools/test/integration/expression_evaluation_test.dart
+++ b/packages/flutter_tools/test/integration/expression_evaluation_test.dart
@@ -13,24 +13,21 @@ import '../src/common.dart';
 import 'test_data/basic_project.dart';
 import 'test_driver.dart';
 
-BasicProject _project = new BasicProject();
-FlutterTestDriver _flutter;
-
 void main() {
   group('expression evaluation', () {
+    Directory tempDir;
+    final BasicProject _project = new BasicProject();
+    FlutterTestDriver _flutter;
+
     setUp(() async {
-      final Directory tempDir = await fs.systemTempDirectory.createTemp('test_app');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_expression_test.');
       await _project.setUpIn(tempDir);
       _flutter = new FlutterTestDriver(tempDir);
     });
 
     tearDown(() async {
-      try {
-        await _flutter.stop();
-        _project.cleanup();
-      } catch (e) {
-        // Don't fail tests if we failed to clean up temp folder.
-      }
+      await _flutter.stop();
+      tryToDelete(tempDir);
     });
 
     Future<VMIsolate> breakInBuildMethod(FlutterTestDriver flutter) async {
diff --git a/packages/flutter_tools/test/integration/flutter_attach_test.dart b/packages/flutter_tools/test/integration/flutter_attach_test.dart
index 6a2bace845..68fb836b67 100644
--- a/packages/flutter_tools/test/integration/flutter_attach_test.dart
+++ b/packages/flutter_tools/test/integration/flutter_attach_test.dart
@@ -11,26 +11,22 @@ import '../src/context.dart';
 import 'test_data/basic_project.dart';
 import 'test_driver.dart';
 
-FlutterTestDriver _flutterRun, _flutterAttach;
-BasicProject _project = new BasicProject();
-
 void main() {
+  FlutterTestDriver _flutterRun, _flutterAttach;
+  final BasicProject _project = new BasicProject();
+  Directory tempDir;
 
   setUp(() async {
-    final Directory tempDir = await fs.systemTempDirectory.createTemp('test_app');
+    tempDir = fs.systemTempDirectory.createTempSync('flutter_attach_test.');
     await _project.setUpIn(tempDir);
     _flutterRun = new FlutterTestDriver(tempDir);
     _flutterAttach = new FlutterTestDriver(tempDir);
   });
 
   tearDown(() async {
-    try {
-      await _flutterRun.stop();
-      await _flutterAttach.stop();
-      _project.cleanup();
-    } catch (e) {
-      // Don't fail tests if we failed to clean up temp folder.
-    }
+    await _flutterRun.stop();
+    await _flutterAttach.stop();
+    tryToDelete(tempDir);
   });
 
   group('attached process', () {
diff --git a/packages/flutter_tools/test/integration/flutter_tester_test.dart b/packages/flutter_tools/test/integration/flutter_tester_test.dart
index e3d2575cb6..6b98e192cc 100644
--- a/packages/flutter_tools/test/integration/flutter_tester_test.dart
+++ b/packages/flutter_tools/test/integration/flutter_tester_test.dart
@@ -19,19 +19,14 @@ void main() {
   Directory oldCurrentDir;
 
   setUp(() async {
-    tempDir = await fs.systemTempDirectory.createTemp('flutter_tester_device');
+    tempDir = fs.systemTempDirectory.createTempSync('flutter_tester_device_test.');
     oldCurrentDir = fs.currentDirectory;
     fs.currentDirectory = tempDir;
   });
 
   tearDown(() {
     fs.currentDirectory = oldCurrentDir;
-    try {
-      tempDir?.deleteSync(recursive: true);
-      tempDir = null;
-    } catch (e) {
-      // Ignored.
-    }
+    tryToDelete(tempDir);
   });
 
   group('FlutterTesterDevice', () {
diff --git a/packages/flutter_tools/test/integration/hot_reload_test.dart b/packages/flutter_tools/test/integration/hot_reload_test.dart
index 58e6ddff58..7d721ca01d 100644
--- a/packages/flutter_tools/test/integration/hot_reload_test.dart
+++ b/packages/flutter_tools/test/integration/hot_reload_test.dart
@@ -12,24 +12,21 @@ import '../src/common.dart';
 import 'test_data/basic_project.dart';
 import 'test_driver.dart';
 
-BasicProject _project = new BasicProject();
-FlutterTestDriver _flutter;
-
 void main() {
   group('hot reload', () {
+    Directory tempDir;
+    final BasicProject _project = new BasicProject();
+    FlutterTestDriver _flutter;
+
     setUp(() async {
-      final Directory tempDir = await fs.systemTempDirectory.createTemp('test_app');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_hot_reload_test_app.');
       await _project.setUpIn(tempDir);
       _flutter = new FlutterTestDriver(tempDir);
     });
 
     tearDown(() async {
-      try {
-        await _flutter.stop();
-        _project.cleanup();
-      } catch (e) {
-        // Don't fail tests if we failed to clean up temp folder.
-      }
+      await _flutter.stop();
+      tryToDelete(tempDir);
     });
 
     test('works without error', () async {
diff --git a/packages/flutter_tools/test/integration/lifetime_test.dart b/packages/flutter_tools/test/integration/lifetime_test.dart
index 10336a609a..79576da088 100644
--- a/packages/flutter_tools/test/integration/lifetime_test.dart
+++ b/packages/flutter_tools/test/integration/lifetime_test.dart
@@ -12,9 +12,6 @@ import '../src/common.dart';
 import 'test_data/basic_project.dart';
 import 'test_driver.dart';
 
-BasicProject _project = new BasicProject();
-FlutterTestDriver _flutter;
-
 /// This duration is arbitrary but is ideally:
 /// a) long enough to ensure that if the app is crashing at startup, we notice
 /// b) as short as possible, to avoid inflating build times
@@ -22,15 +19,19 @@ const Duration requiredLifespan = Duration(seconds: 5);
 
 void main() {
   group('flutter run', () {
+    final BasicProject _project = new BasicProject();
+    FlutterTestDriver _flutter;
+    Directory tempDir;
+
     setUp(() async {
-      final Directory tempDir = await fs.systemTempDirectory.createTemp('test_app');
+      tempDir = fs.systemTempDirectory.createTempSync('flutter_lifetime_test.');
       await _project.setUpIn(tempDir);
       _flutter = new FlutterTestDriver(tempDir);
     });
 
     tearDown(() async {
       await _flutter.stop();
-      _project.cleanup();
+      tryToDelete(tempDir);
     });
 
     test('does not terminate when a debugger is attached', () async {
diff --git a/packages/flutter_tools/test/integration/test_data/test_project.dart b/packages/flutter_tools/test/integration/test_data/test_project.dart
index af825d261b..1b73c45c1b 100644
--- a/packages/flutter_tools/test/integration/test_data/test_project.dart
+++ b/packages/flutter_tools/test/integration/test_data/test_project.dart
@@ -26,10 +26,6 @@ abstract class TestProject {
     await getPackages(dir.path);
   }
 
-  void cleanup() {
-    dir?.deleteSync(recursive: true);
-  }
-
   int lineContaining(String contents, String search) {
     final int index = contents.split('\n').indexWhere((String l) => l.contains(search));
     if (index == -1)
diff --git a/packages/flutter_tools/test/integration/test_driver.dart b/packages/flutter_tools/test/integration/test_driver.dart
index 0df87924cc..ee9a76d62c 100644
--- a/packages/flutter_tools/test/integration/test_driver.dart
+++ b/packages/flutter_tools/test/integration/test_driver.dart
@@ -23,6 +23,8 @@ const Duration appStartTimeout = Duration(seconds: 60);
 const Duration quitTimeout = Duration(seconds: 5);
 
 class FlutterTestDriver {
+  FlutterTestDriver(this._projectFolder);
+
   final Directory _projectFolder;
   Process _proc;
   int _procPid;
@@ -36,8 +38,6 @@ class FlutterTestDriver {
   int _vmServicePort;
   bool _hasExited = false;
 
-  FlutterTestDriver(this._projectFolder);
-
   VMServiceClient vmService;
   String get lastErrorInfo => _errorBuffer.toString();
   int get vmServicePort => _vmServicePort;
@@ -318,24 +318,24 @@ class FlutterTestDriver {
   int id = 1;
   Future<dynamic> _sendRequest(String method, dynamic params) async {
     final int requestId = id++;
-    final Map<String, dynamic> req = <String, dynamic>{
+    final Map<String, dynamic> request = <String, dynamic>{
       'id': requestId,
       'method': method,
       'params': params
     };
-    final String jsonEncoded = json.encode(<Map<String, dynamic>>[req]);
+    final String jsonEncoded = json.encode(<Map<String, dynamic>>[request]);
     _debugPrint(jsonEncoded);
 
     // Set up the response future before we send the request to avoid any
     // races.
     final Future<Map<String, dynamic>> responseFuture = _waitFor(id: requestId);
     _proc.stdin.writeln(jsonEncoded);
-    final Map<String, dynamic> resp = await responseFuture;
+    final Map<String, dynamic> response = await responseFuture;
 
-    if (resp['error'] != null || resp['result'] == null)
+    if (response['error'] != null || response['result'] == null)
       _throwErrorResponse('Unexpected error response');
 
-    return resp['result'];
+    return response['result'];
   }
 
   void _throwErrorResponse(String msg) {
diff --git a/packages/flutter_tools/test/src/common.dart b/packages/flutter_tools/test/src/common.dart
index 3aa0331de2..b932cf8517 100644
--- a/packages/flutter_tools/test/src/common.dart
+++ b/packages/flutter_tools/test/src/common.dart
@@ -22,6 +22,17 @@ export 'package:test/test.dart' hide TypeMatcher, isInstanceOf; // Defines a 'pa
 // TODO(ianh): Remove this once https://github.com/dart-lang/matcher/issues/98 is fixed
 Matcher isInstanceOf<T>() => new test_package.TypeMatcher<T>(); // ignore: prefer_const_constructors, https://github.com/dart-lang/sdk/issues/32544
 
+void tryToDelete(Directory directory) {
+  // This should not be necessary, but it turns out that
+  // on Windows it's common for deletions to fail due to
+  // bogus (we think) "access denied" errors.
+  try {
+    directory.deleteSync(recursive: true);
+  } on FileSystemException catch (error) {
+    print('Failed to delete ${directory.path}: $error');
+  }
+}
+
 /// Gets the path to the root of the Flutter repository.
 ///
 /// This will first look for a `FLUTTER_ROOT` environment variable. If the
diff --git a/packages/flutter_tools/test/src/context.dart b/packages/flutter_tools/test/src/context.dart
index 0136da1427..c366633557 100644
--- a/packages/flutter_tools/test/src/context.dart
+++ b/packages/flutter_tools/test/src/context.dart
@@ -48,13 +48,16 @@ void testUsingContext(String description, dynamic testMethod(), {
   // leak a sticky $HOME/.flutter_settings behind!
   Directory configDir;
   tearDown(() {
-    configDir?.deleteSync(recursive: true);
-    configDir = null;
+    if (configDir != null) {
+      tryToDelete(configDir);
+      configDir = null;
+    }
   });
   Config buildConfig(FileSystem fs) {
-    configDir = fs.systemTempDirectory.createTempSync('config-dir');
+    configDir = fs.systemTempDirectory.createTempSync('flutter_config_dir_test.');
     final File settingsFile = fs.file(
-        fs.path.join(configDir.path, '.flutter_settings'));
+      fs.path.join(configDir.path, '.flutter_settings')
+    );
     return new Config(settingsFile);
   }
 
diff --git a/packages/flutter_tools/test/src/mocks.dart b/packages/flutter_tools/test/src/mocks.dart
index 19e6e45574..a4326e0db6 100644
--- a/packages/flutter_tools/test/src/mocks.dart
+++ b/packages/flutter_tools/test/src/mocks.dart
@@ -44,7 +44,7 @@ class MockAndroidSdk extends Mock implements AndroidSdk {
     bool withNdkSysroot = false,
     bool withSdkManager = true,
   }) {
-    final Directory dir = fs.systemTempDirectory.createTempSync('android-sdk');
+    final Directory dir = fs.systemTempDirectory.createTempSync('flutter_mock_android_sdk.');
 
     _createSdkFile(dir, 'platform-tools/adb');
 
@@ -66,18 +66,23 @@ class MockAndroidSdk extends Mock implements AndroidSdk {
 
     if (withNdkDir != null) {
       final String ndkCompiler = fs.path.join(
-          'ndk-bundle',
-          'toolchains',
-          'arm-linux-androideabi-4.9',
-          'prebuilt',
-          withNdkDir,
-          'bin',
-          'arm-linux-androideabi-gcc');
+        'ndk-bundle',
+        'toolchains',
+        'arm-linux-androideabi-4.9',
+        'prebuilt',
+        withNdkDir,
+        'bin',
+        'arm-linux-androideabi-gcc',
+      );
       _createSdkFile(dir, ndkCompiler);
     }
     if (withNdkSysroot) {
-      final String armPlatform =
-          fs.path.join('ndk-bundle', 'platforms', 'android-9', 'arch-arm');
+      final String armPlatform = fs.path.join(
+        'ndk-bundle',
+        'platforms',
+        'android-9',
+        'arch-arm',
+      );
       _createDir(dir, armPlatform);
     }