Add test to compare-failures

tools/gardening/lib/src/compare_failures_impl.dart

Index: tools/gardening/lib/src/compare_failures_impl.dart
diff --git a/tools/gardening/bin/compare_failures.dart b/tools/gardening/lib/src/compare_failures_impl.dart
similarity index 71%
copy from tools/gardening/bin/compare_failures.dart
copy to tools/gardening/lib/src/compare_failures_impl.dart
index de888914be7afeb83cc238627fb96899dad3d456..d3d77198061be4d9de8b975fb5ff855a0099b324 100644
--- a/tools/gardening/bin/compare_failures.dart
+++ b/tools/gardening/lib/src/compare_failures_impl.dart
@@ -7,53 +7,56 @@
 /// Use this to detect flakiness of failures, especially timeouts.
 
 import 'dart:async';
-import 'dart:io';
 
-import 'package:args/args.dart';
 import 'package:gardening/src/buildbot_structures.dart';
+import 'package:gardening/src/buildbot_data.dart';
 import 'package:gardening/src/client.dart';
 import 'package:gardening/src/util.dart';
 
-void help(ArgParser argParser) {
-  print('Given a <log-uri> finds all failing tests in that stdout. Then ');
-  print('fetches earlier runs of the same bot and compares the results.');
-  print('This tool is particularly useful to detect flakes and their ');
-  print('frequency.');
-  print('Usage: compare_failures [options] <log-uri>');
-  print('where <log-uri> is the uri the stdio output of a failing test step');
-  print('and options are:');
-  print(argParser.usage);
+Future mainInternal(BuildbotClient client, List<String> args,
+    {int runCount: 10}) async {
+  printBuildResultsSummary(
+      await loadBuildResults(client, args, runCount: runCount));
 }
 
-main(List<String> args) async {
-  ArgParser argParser = createArgParser();
-  argParser.addOption("run-count",
-      defaultsTo: "10", help: "How many previous runs should be fetched");
-  ArgResults argResults = argParser.parse(args);
-  processArgResults(argResults);
-
-  BuildbotClient client = argResults['logdog']
-      ? new LogdogBuildbotClient()
-      : new HttpBuildbotClient();
-
-  var runCount = int.parse(argResults['run-count'], onError: (_) => null);
-
-  if (argResults.rest.length != 1 || argResults['help'] || runCount == null) {
-    help(argParser);
-    if (argResults['help']) return;
-    exit(1);
+/// Loads [BuildResult]s for the [runCount] last builds for the build(s) in
+/// [args]. [args] can be a list of [BuildGroup] names or a list of log uris.
+Future<Map<BuildUri, List<BuildResult>>> loadBuildResults(
+    BuildbotClient client, List<String> args,
+    {int runCount: 10}) async {
+  List<BuildUri> buildUriList = <BuildUri>[];
+  for (BuildGroup buildGroup in buildGroups) {
+    if (args.contains(buildGroup.groupName)) {
+      buildUriList.addAll(buildGroup.createUris(client.mostRecentBuildNumber));
+    }
+  }
+  if (buildUriList.isEmpty) {
+    for (String url in args) {
+      if (!url.endsWith('/text')) {
+        // Use the text version of the stdio log.
+        url += '/text';
+      }
+      Uri uri = Uri.parse(url);
+      BuildUri buildUri = new BuildUri(uri);
+      buildUriList.add(buildUri);
+    }
   }
-  String url = argResults.rest.first;
-  if (!url.endsWith('/text')) {
-    // Use the text version of the stdio log.
-    url += '/text';
+  Map<BuildUri, List<BuildResult>> buildResults =
+      <BuildUri, List<BuildResult>>{};
+  for (BuildUri buildUri in buildUriList) {
+    List<BuildResult> results =
+        await readBuildResults(client, buildUri, runCount);
+    buildResults[buildUri] = results;
   }
-  Uri uri = Uri.parse(url);
-  BuildUri buildUri = new BuildUri(uri);
-  List<BuildResult> results =
-      await readBuildResults(client, buildUri, runCount);
-  print(generateBuildResultsSummary(buildUri, results));
-  client.close();
+  return buildResults;
+}
+
+/// Prints summaries for the [buildResults].
+// TODO(johnniwinther): Improve printing of multiple [BuildUri] results.
+void printBuildResultsSummary(Map<BuildUri, List<BuildResult>> buildResults) {
+  buildResults.forEach((BuildUri buildUri, List<BuildResult> results) {
+    print(generateBuildResultsSummary(buildUri, results));
+  });
 }
 
 /// Creates a [BuildResult] for [buildUri] and, if it contains failures, the
@@ -154,5 +157,8 @@ String generateBuildResultsSummary(
       sb.write('\n');
     });
   }
+  if (timeoutIds.isEmpty && errorIds.isEmpty) {
+    sb.write('No errors found.');
+  }
   return sb.toString();
 }