Add test for driver test organisation (#75271)

packages/flutter_driver/test/src/real_tests/test_organisation_test.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// 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:flutter_driver/flutter_driver.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  // On CI we only execute the tests in the `test/src/real_test` and
+  // `test/src/web_test` directory, see https://github.com/flutter/flutter/blob/master/dev/bots/test.dart.
+  // This test ensures that we do not accidentally add tests in the the `test`
+  // or `test/src` directory, which would not run on CI.
+  test('test files exist only in directories where CI expects them', () {
+    final String flutterDriverPath = fs.path.dirname(Platform.script.path);
+    expect(fs.path.basename(flutterDriverPath), 'flutter_driver');
+    final String flutterDriverTestPath = fs.path.join(flutterDriverPath, 'test');
+    final Directory flutterDriverTestDir = fs.directory(flutterDriverTestPath);
+    expect(flutterDriverTestDir.existsSync(), isTrue, reason: '${flutterDriverTestDir.path} does not exist.');
+    final List<String> filesInTestDir = flutterDriverTestDir.listSync()
+        .map((FileSystemEntity e) => fs.path.basename(e.path))
+        .where((String s) => fs.path.extension(s) == '.dart')
+        .toList();
+
+    // There are no test files in the `test` directory.
+    expect(filesInTestDir, <String>['common.dart']);
+
+    // There are no test files in the src directory.
+    final String flutterDriverTestSrcPath = fs.path.join(flutterDriverTestPath, 'src');
+    final Directory flutterDriverTestSrcDir = fs.directory(flutterDriverTestSrcPath);
+    expect(flutterDriverTestSrcDir.existsSync(), isTrue, reason: '${flutterDriverTestSrcDir.path} does not exist.');
+    final List<String> filesInTestSrcDir = flutterDriverTestSrcDir.listSync()
+        .map((FileSystemEntity e) => fs.path.basename(e.path))
+        .where((String s) => fs.path.extension(s) == '.dart')
+        .toList();
+
+    // There are no test files in the `test/src` directory.
+    expect(filesInTestSrcDir, unorderedEquals(<String>[]));
+  }, skip: Platform.isWindows);
+}