Ensure that the output path used by perf_tests_test matches the path used by perf_tests if the FLUTTER_TEST_OUTPUTS_DIR variable is set (#153888)

A recent change to the flutter_drone recipe is setting FLUTTER_TEST_OUTPUTS_DIR in the environment (see https://flutter.googlesource.com/recipes/+/b111cd3ef2297e66905cc48c2cfedce0cf1ba46f)

If FLUTTER_TEST_OUTPUTS_DIR is set, then perf_tests will use an output path based on that variable.  perf_tests_test needs to use the same logic when looking for the expected output file.

Author: jason-simmons

dev/devicelab/lib/tasks/perf_tests.dart

@@ -21,7 +21,7 @@ import '../framework/utils.dart';
 /// Must match flutter_driver/lib/src/common.dart.
 ///
 /// Redefined here to avoid taking a dependency on flutter_driver.
-String _testOutputDirectory(String testDirectory) {
+String testOutputDirectory(String testDirectory) {
   return Platform.environment['FLUTTER_TEST_OUTPUTS_DIR'] ?? '$testDirectory/build';
 }
 
@@ -484,7 +484,7 @@ TaskFunction createsScrollSmoothnessPerfTest() {
         deviceId,
       ]);
       final Map<String, dynamic> data = json.decode(
-        file('${_testOutputDirectory(testDirectory)}/scroll_smoothness_test.json').readAsStringSync(),
+        file('${testOutputDirectory(testDirectory)}/scroll_smoothness_test.json').readAsStringSync(),
       ) as Map<String, dynamic>;
 
       final Map<String, dynamic> result = <String, dynamic>{};
@@ -535,7 +535,7 @@ TaskFunction createFramePolicyIntegrationTest() {
         deviceId,
       ]);
       final Map<String, dynamic> data = json.decode(
-        file('${_testOutputDirectory(testDirectory)}/frame_policy_event_delay.json').readAsStringSync(),
+        file('${testOutputDirectory(testDirectory)}/frame_policy_event_delay.json').readAsStringSync(),
       ) as Map<String, dynamic>;
       final Map<String, dynamic> fullLiveData = data['fullyLive'] as Map<String, dynamic>;
       final Map<String, dynamic> benchmarkLiveData = data['benchmarkLive'] as Map<String, dynamic>;
@@ -1025,7 +1025,7 @@ class StartupTest {
         timer.cancel();
         if (result == 0) {
           final Map<String, dynamic> data = json.decode(
-            file('${_testOutputDirectory(testDirectory)}/start_up_info.json').readAsStringSync(),
+            file('${testOutputDirectory(testDirectory)}/start_up_info.json').readAsStringSync(),
           ) as Map<String, dynamic>;
           results.add(data);
         } else {
@@ -1418,7 +1418,7 @@ class PerfTest {
       }
 
       final Map<String, dynamic> data = json.decode(
-        file('${_testOutputDirectory(testDirectory)}/$resultFilename.json').readAsStringSync(),
+        file('${testOutputDirectory(testDirectory)}/$resultFilename.json').readAsStringSync(),
       ) as Map<String, dynamic>;
 
       if (data['frame_count'] as int < 5) {
@@ -1451,7 +1451,7 @@ class PerfTest {
         data,
         detailFiles: <String>[
           if (saveTraceFile)
-            '${_testOutputDirectory(testDirectory)}/$traceFilename.json',
+            '${testOutputDirectory(testDirectory)}/$traceFilename.json',
         ],
         benchmarkScoreKeys: benchmarkScoreKeys ?? <String>[
           ..._kCommonScoreKeys,

dev/devicelab/test/perf_tests_test.dart

@@ -16,9 +16,11 @@ void main() {
   late Directory testDirectory;
   late File testTarget;
   late Device device;
+  late String perfTestOutputPath;
 
   setUp(() async {
     testDirectory = Directory.systemTemp.createTempSync('test_dir');
+    perfTestOutputPath = testOutputDirectory(testDirectory.absolute.path);
     testTarget = File('${testDirectory.absolute.path}/test_file')..createSync();
     device = const FakeDevice(deviceId: 'fakeDeviceId');
     deviceOperatingSystem = DeviceOperatingSystem.fake;
@@ -64,7 +66,7 @@ void main() {
     };
     const String resultFileName = 'fake_result';
     void driveCallback(List<String> arguments) {
-      final File resultFile = File('${testDirectory.absolute.path}/build/$resultFileName.json')..createSync(recursive: true);
+      final File resultFile = File('$perfTestOutputPath/$resultFileName.json')..createSync(recursive: true);
       resultFile.writeAsStringSync(json.encode(fakeData));
     }
     final PerfTest perfTest = PerfTest(testDirectory.absolute.path, testTarget.absolute.path, 'test_file', resultFilename: resultFileName, device: device, flutterDriveCallback: driveCallback);
@@ -117,7 +119,7 @@ void main() {
     };
     const String resultFileName = 'fake_result';
     void driveCallback(List<String> arguments) {
-      final File resultFile = File('${testDirectory.absolute.path}/build/$resultFileName.json')..createSync(recursive: true);
+      final File resultFile = File('$perfTestOutputPath/$resultFileName.json')..createSync(recursive: true);
       resultFile.writeAsStringSync(json.encode(fakeData));
     }
     final PerfTest perfTest = PerfTest(testDirectory.absolute.path, testTarget.absolute.path, 'test_file', resultFilename: resultFileName, device: device, flutterDriveCallback: driveCallback);