Add test to compare-failures

tools/gardening/test/compare_failures_test.dart

Index: tools/gardening/test/compare_failures_test.dart
diff --git a/tools/gardening/test/compare_failures_test.dart b/tools/gardening/test/compare_failures_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..d7cc9e526cbb2d730915cf65e37cd121ebe00b37
--- /dev/null
+++ b/tools/gardening/test/compare_failures_test.dart
@@ -0,0 +1,79 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Compares the test log of a build step with previous builds.
+///
+/// Use this to detect flakiness of failures, especially timeouts.
+
+import 'dart:async';
+
+import 'package:args/args.dart';
+import 'package:expect/expect.dart';
+import 'package:gardening/src/buildbot_structures.dart';
+import 'package:gardening/src/client.dart';
+import 'package:gardening/src/compare_failures_impl.dart';
+import 'package:gardening/src/util.dart';
+
+import 'test_client.dart';
+
+main(List<String> args) async {
+  ArgParser argParser = createArgParser();
+  argParser.addFlag('force', abbr: 'f');
+  ArgResults argResults = argParser.parse(args);
+  processArgResults(argResults);
+  bool force = argResults['force'];
+
+  BuildbotClient client = argResults['logdog']
+      ? new LogdogBuildbotClient()
+      : new TestClient(force: force);
+
+  await runSingleTest(
+      client,
+      'https://build.chromium.org/p/client.dart/builders/'
+      'vm-kernel-linux-debug-x64-be/builds/1884/steps/'
+      'vm%20tests/logs/stdio',
+      1,
+      {
+        1884: {
+          'dartk-vm debug_x64 corelib_2/map_keys2_test': 'RuntimeError/Pass',
+        },
+        1883: {
+          'dartk-vm debug_x64 corelib_2/map_keys2_test': 'RuntimeError/Pass',
+          'dartk-vm debug_x64 corelib_2/package_resource_test':
+              'Pass/CompileTimeError',
+        },
+      });
+
+  client.close();
+}
+
+testSingleResults(
+    Map<int, Map<String, String>> expected, List<BuildResult> results) {
+  Expect.equals(expected.length, results.length);
+  int i = 0;
+  expected.forEach((int buildNumber, Map<String, String> failures) {
+    BuildResult result = results[i++];
+    Expect.equals(failures.length, result.errors.length);
+    failures.forEach((String testName, String resultText) {
+      List<String> nameParts = split(testName, [' ', ' ']);
+      TestConfiguration id =
+          new TestConfiguration(nameParts[0], nameParts[1], nameParts[2]);
+      List<String> resultParts = split(resultText, ['/']);
+      TestFailure failure = result.errors.singleWhere((t) => t.id == id);
+      Expect.equals(failure.expected, resultParts[0]);
+      Expect.equals(failure.actual, resultParts[1]);
+    });
+  });
+}
+
+Future runSingleTest(BuildbotClient client, String testUri, int runCount,
+    Map<int, Map<String, String>> expectedResult) async {
+  Map<BuildUri, List<BuildResult>> buildResults =
+      await loadBuildResults(client, [testUri], runCount: runCount);
+  if (LOG) {
+    printBuildResultsSummary(buildResults);
+  }
+  Expect.equals(1, buildResults.length);
+  testSingleResults(expectedResult, buildResults.values.first);
+}