diff --git a/.gitignore b/.gitignore
index 0716c03d..f6b15678 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
+.dart_tool
 .packages
 .pub
 packages
@@ -26,3 +27,4 @@ test_reports/
 /test_fixtures/dart_x_only/doc/api/
 /test_fixtures/docs/docs/doc/api/
 /test_fixtures/format/changes_needed_temp/
+/test_fixtures/needs_build_runner/.dart_tool
\ No newline at end of file
diff --git a/lib/src/tasks/test/api.dart b/lib/src/tasks/test/api.dart
index e25aeeea..47ba9654 100644
--- a/lib/src/tasks/test/api.dart
+++ b/lib/src/tasks/test/api.dart
@@ -24,12 +24,13 @@ import 'package:dart_dev/src/util.dart'
     show dartMajorVersion, dartiumExpirationOverrideEnv;
 import 'package:dart_dev/util.dart' show hasImmediateDependency;
 
-TestTask test(
-    {int concurrency,
-    List<String> platforms: const [],
-    List<String> presets: const [],
-    List<String> testArgs: const [],
-    List<String> tests: const []}) {
+TestTask test({
+  int concurrency,
+  List<String> platforms: const [],
+  List<String> presets: const [],
+  List<String> testArgs: const [],
+  List<String> tests: const [],
+}) {
   final executable = 'pub';
   final args = <String>[];
 
@@ -43,7 +44,12 @@ TestTask test(
     }
 
     if (hasImmediateDependency('build_test')) {
-      args.addAll(['run', 'build_runner', 'test', '--']);
+      args.addAll([
+        'run',
+        'build_runner',
+        'test',
+        '--',
+      ]);
     } else {
       args.addAll(['run', 'test']);
     }
diff --git a/lib/src/tasks/test/cli.dart b/lib/src/tasks/test/cli.dart
index a68248c0..8b48e1fe 100644
--- a/lib/src/tasks/test/cli.dart
+++ b/lib/src/tasks/test/cli.dart
@@ -55,6 +55,8 @@ class TestCli extends TaskCli {
             'Implies --concurrency=1 and --timeout=none.\n'
             'Currently only supported for browser tests.',
         negatable: false)
+    ..addFlag('delete-conflicting-outputs',
+        help: 'Deletes conflicting outputs during the build', negatable: false)
     ..addOption('pub-serve-port',
         help:
             'Port used by the Pub server for browser tests. The default value will randomly select an open port to use.')
@@ -93,6 +95,7 @@ class TestCli extends TaskCli {
 
     final testArgs = <String>[];
     List<String> tests = [];
+    List<String> buildArgs = [];
 
     if (!color) {
       testArgs.add('--no-color');
@@ -123,6 +126,11 @@ class TestCli extends TaskCli {
     List<String> presets =
         TaskCli.valueOf('preset', parsedArgs, const <String>[]);
 
+    bool deleteConflictingOutputs = TaskCli.valueOf(
+        'delete-conflicting-outputs',
+        parsedArgs,
+        config.test.deleteConflictingOutputs);
+
     // CLI user can specify individual test files to run.
     bool individualTestsSpecified = parsedArgs.rest.isNotEmpty;
 
@@ -184,9 +192,13 @@ class TestCli extends TaskCli {
       testArgs.add('--pause-after-load');
     }
 
+    if (deleteConflictingOutputs) {
+      buildArgs.add('--delete-conflicting-outputs');
+    }
+
     if (dartMajorVersion == 2 && hasImmediateDependency('build_test')) {
-      final buildProcess =
-          new TaskProcess('pub', ['run', 'build_runner', 'build']);
+      var args = ['run', 'build_runner', 'build']..addAll(buildArgs);
+      final buildProcess = new TaskProcess('pub', args);
       reporter.logGroup('pub run build_runner build',
           outputStream: buildProcess.stdout, errorStream: buildProcess.stderr);
       final buildExitCode = await buildProcess.exitCode;
diff --git a/lib/src/tasks/test/config.dart b/lib/src/tasks/test/config.dart
index 782dd2dc..0603495b 100644
--- a/lib/src/tasks/test/config.dart
+++ b/lib/src/tasks/test/config.dart
@@ -19,6 +19,7 @@ import 'package:dart_dev/src/tasks/config.dart';
 const List defaultAfterFunctional = const [];
 const List defaultBeforeFunctional = const [];
 const int defaultConcurrency = 4;
+const bool defaultDeleteConflictingOutputs = false;
 const bool defaultPauseAfterLoad = false;
 const bool defaultPubServe = false;
 const bool defaultDisableServeStdOut = false;
@@ -35,6 +36,7 @@ class TestConfig extends TaskConfig {
   List afterFunctionalTests = defaultAfterFunctional;
   List beforeFunctionalTests = defaultBeforeFunctional;
   int concurrency = defaultConcurrency;
+  bool deleteConflictingOutputs = defaultDeleteConflictingOutputs;
   List<String> functionalTests = defaultFunctionalTests;
   List<String> integrationTests = defaultIntegrationTests;
   List<String> platforms = defaultPlatforms;