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毛昱楓 Mao Yufeng
2019年度 新卒入社
株式会社サイバーエージェント
@lcdsmao
@lcdsmao
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DartのFutureとStreamを用いた
非同期コードをテストするためのアプローチ
を紹介します。
Content
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How to write test
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Add test dependency
# pubspec.yaml
dev_dependencies:
# If this is a dart package
test: ^1.17.4
# If this is a flutter package
flutter_test:
sdk: flutter
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How to write test
// Test target
int addOne(int num) => num + 1;
// Tests are specified using the test() function
// Test assertions are made using expect()
void main() {
test('test add 1', () {
expect(addOne(9), 10);
// Or using matcher
expect(addOne(9), equals(10));
});
}
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How to write test
// Test target
int addOne(int num) => num + 1;
// Tests are specified using the test() function
// Test assertions are made using expect()
void main() {
test('test add 1', () {
expect(addOne(9), 10);
// Or using matcher
expect(addOne(9), equals(10));
});
}
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How to write test
// Test target
int addOne(int num) => num + 1;
// Tests are specified using the test() function
// Test assertions are made using expect()
void main() {
test('test add 1', () {
expect(addOne(9), 10);
// Or using matcher
expect(addOne(9), equals(10));
});
}
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How to write test
// Test target
int addOne(int num) => num + 1;
// Tests are specified using the test() function
// Test assertions are made using expect()
void main() {
test('test add 1', () {
expect(addOne(9), 10);
// Or using matcher
expect(addOne(9), equals(10));
});
}
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Test Future
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Test Future
// Test target
Future addOneAsync(int num) async => num + 1;
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Test Future
void main() {
test('Test addOneAsync via completion matcher', () {
Future data = addOneAsync(9);
expect(data, completion(10));
});
test('Test addOneAsync via async/await', () async {
int data = await addOneAsync(9);
expect(data, 10);
});
}
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Test Future
void main() {
test('Test addOneAsync via completion matcher', () {
Future data = addOneAsync(9);
expect(data, completion(10));
});
test('Test addOneAsync via async/await', () async {
int data = await addOneAsync(9);
expect(data, 10);
});
}
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Test Future
void main() {
test('Test addOneAsync via completion matcher', () {
Future data = addOneAsync(9);
expect(data, completion(10));
});
test('Test addOneAsync via async/await', () async {
int data = await addOneAsync(9);
expect(data, 10);
});
}
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Test Future error
// Test target
Future willThrowException() async => throw Exception();
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Test Future error
void main() {
test('Test future error via throwsException matcher', () {
expect(willThrowException(), throwsException);
});
}
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Test hidden async operations
// Test target
class Counter {
var value = 9;
void addOne() {
Future(() => value = value + 1);
}
}
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Test hidden async operations
void main() {
test('test counter addOne', () {
final counter = Counter();
counter.addOne();
// Assertion will fail, counter.value is still 9.
expect(counter.value, 10);
});
}
Assertion時点に、addOne中のFuture
タスクはまだ実行されていません
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Event loop
Dartはシングルスレッド言語です。
Event loop で一度に1つのイベントのみを処理します。
https://youtu.be/vl_AaCgudcY?t=165
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void main() {
test('test counter addOne', () {
final counter = Counter();
counter.addOne();
expect(counter.value, 10);
});
}
Test hidden async operations
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void main() {
test('test counter addOne', () async {
final counter = Counter();
counter.addOne();
// Let event loop handling the addOne task before assertion
await Future(() {});
expect(counter.value, 10);
});
}
Assertionする前に、Event loopの
タスク処理を待ちます
Test hidden async operations
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Test hidden async operations
void main() {
test('test counter addOne', () async {
final counter = Counter();
counter.addOne();
// Let event loop handling the addOne task before assertion
await pumpEventQueue();
expect(counter.value, 10);
});
}
Assertionする前に、Event loopの
タスク処理を待ちます
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Test Stream
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Test Stream
void main() {
test('test stream', () {
final stream = Stream.fromIterable(['CA', 'Base', 'Next']);
expect(stream, emitsInOrder(['CA', 'Base', 'Next', emitsDone]));
});
}
emitsXxxの命名のような、
他のStreamMatecherもあります
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Test Stream interactively
class Counter {
var _value = 0;
final _valueStream = StreamController.broadcast();
// Test target
Stream get valueStream => _valueStream.stream;
void addOne() {
_value = _value + 1;
_valueStream.add(_value);
}
}
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Test Stream interactively
void main() {
test('test counter stream', () {
final counter = Counter();
counter.addOne();
counter.addOne();
counter.addOne();
// Assertion fail 😵
expect(counter.valueStream, emitsInOrder([1, 2, 3]));
});
}
Assertionする時点、値もうすでに
流れていました
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Test Stream interactively
void main() {
test('test counter stream', () {
final counter = Counter();
// Assert before any opertions
expect(counter.valueStream, emitsInOrder([1, 2, 3]));
});
}
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Test Stream interactively
void main() {
test('test counter stream', () {
final counter = Counter();
// Assert before any opertions
expect(counter.valueStream, emitsInOrder([1, 2, 3]));
});
}
Streamの値が変化する前に
Assertionします
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Test Stream interactively
void main() {
test('test counter stream', () {
final counter = Counter();
// Assert before any opertions
expect(counter.valueStream, emitsInOrder([1, 2, 3]));
counter.addOne();
counter.addOne();
counter.addOne();
});
}
Streamの値が変化する前に
Assertionします
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Recap
• Future/Stream のテストには
test package が提供する Matcher を使いましょう
• 隠された非同期処理をテストするには
pumpEventQueue で処理を待ちましょう
• 先に expect を呼んで、
後で発生する非同期処理をテストしましょう
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