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Side by Side Diff: mojo/dart/testing/async_helper.dart

Issue 1132063007: Rationalize Dart mojo and sky package structure (Closed) Base URL: https://github.com/domokit/mojo.git@master
Patch Set: Created 5 years, 7 months ago
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1 // Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
2 // for details. All rights reserved. Use of this source code is governed by a
3 // BSD-style license that can be found in the LICENSE file.
4
5 /// This library is used for testing asynchronous tests.
6 /// If a test is asynchronous, it needs to notify the testing driver
7 /// about this (otherwise tests may get reported as passing [after main()
8 /// finished] even if the asynchronous operations fail).
9 /// Tests which can't use the unittest framework should use the helper functions
10 /// in this library.
11 /// This library provides four methods
12 /// - asyncStart(): Needs to be called before an asynchronous operation is
13 /// scheduled.
14 /// - asyncEnd(): Needs to be called as soon as the asynchronous operation
15 /// ended.
16 /// - asyncSuccess(_): Variant of asyncEnd useful together with Future.then.
17 /// - asyncTest(f()): Helper method that wraps a computation that returns a
18 /// Future with matching calls to asyncStart() and
19 /// asyncSuccess(_).
20 /// After the last asyncStart() called was matched with a corresponding
21 /// asyncEnd() or asyncSuccess(_) call, the testing driver will be notified that
22 /// the tests is done.
23
24 library async_helper;
25
26 // TODO(kustermann): This is problematic because we rely on a working
27 // 'dart:isolate' (i.e. it is in particular problematic with dart2js).
28 // It would be nice if we could use a different mechanism for different
29 // runtimes.
30 import 'dart:isolate';
31
32 bool _initialized = false;
33 ReceivePort _port = null;
34 int _asyncLevel = 0;
35
36 Exception _buildException(String msg) {
37 return new Exception('Fatal: $msg. This is most likely a bug in your test.');
38 }
39
40 /// Call this method before an asynchronous test is created.
41 void asyncStart() {
42 if (_initialized && _asyncLevel == 0) {
43 throw _buildException('asyncStart() was called even though we are done '
44 'with testing.');
45 }
46 if (!_initialized) {
47 print('unittest-suite-wait-for-done');
48 _initialized = true;
49 _port = new ReceivePort();
50 }
51 _asyncLevel++;
52 }
53
54 /// Call this after an asynchronous test has ended successfully.
55 void asyncEnd() {
56 if (_asyncLevel <= 0) {
57 if (!_initialized) {
58 throw _buildException('asyncEnd() was called before asyncStart().');
59 } else {
60 throw _buildException('asyncEnd() was called more often than '
61 'asyncStart().');
62 }
63 }
64 _asyncLevel--;
65 if (_asyncLevel == 0) {
66 _port.close();
67 _port = null;
68 print('unittest-suite-success');
69 }
70 }
71
72 /**
73 * Call this after an asynchronous test has ended successfully. This is a helper
74 * for calling [asyncEnd].
75 *
76 * This method intentionally has a signature that matches [:Future.then:] as a
77 * convenience for calling [asyncEnd] when a [:Future:] completes without error,
78 * like this:
79 *
80 * asyncStart();
81 * Future result = test();
82 * result.then(asyncSuccess);
83 */
84 void asyncSuccess(_) => asyncEnd();
85
86 /**
87 * Helper method for performing asynchronous tests involving [:Future:].
88 *
89 * [f] must return a [:Future:] for the test computation.
90 */
91 void asyncTest(f()) {
92 asyncStart();
93 f().then(asyncSuccess);
94 }
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