[英]Testing Dart class that runs code on Isolate
I have a Dart class that performs computations on Isolate.我有一个在 Isolate 上执行计算的 Dart class。 Here is my code:
这是我的代码:
class Mapper {
SendPort _isolateSendPort;
Isolate _isolate;
Mapper() {
_asyncInit();
}
void _asyncInit() async {
final receivePort = ReceivePort();
_isolate = await Isolate.spawn(
_mappingFunction,
receivePort.sendPort,
);
_isolateSendPort = await receivePort.first;
}
static void _mappingFunction(SendPort callerSendPort) {
final newIsolateReceivePort = ReceivePort();
callerSendPort.send(newIsolateReceivePort.sendPort);
newIsolateReceivePort.listen((dynamic message) {
final crossIsolatesMessage =
message as CrossIsolatesMessage<Input>;
// some computations...
crossIsolatesMessage.sender.send(output);
});
}
Future<Output> map(Input input) async {
final port = ReceivePort();
_isolateSendPort.send(CrossIsolatesMessage<Input>(
sender: port.sendPort,
message: input,
));
return port.map((event) => event as Output).first;
}
void dispose() {
_isolate?.kill(priority: Isolate.immediate);
_isolate = null;
}
}
class CrossIsolatesMessage<T> {
final SendPort sender;
final T message;
CrossIsolatesMessage({
@required this.sender,
this.message,
});
}
This code works well when I run Flutter app.当我运行 Flutter 应用程序时,此代码运行良好。 But unit test for public method
Future<Output> map(Input input)
throws an error NoSuchMethodError
which meens _isolateSendPort
is null.但是公共方法
Future<Output> map(Input input)
的单元测试会引发错误NoSuchMethodError
,这_isolateSendPort
是 null。
Here is the unit test code:下面是单元测试代码:
test('Mapper map', () {
final sut = Mapper();
final inputDummy = Input('123');
final resultFuture = sut.map(inputDummy);
final expectedResult = Output('321');
expectLater(resultFuture, completion(expectedResult));
});
Here is an error:这是一个错误:
NoSuchMethodError: The method 'send' was called on null.
Receiver: null
Tried calling: send(Instance of 'CrossIsolatesMessage<Input>')
dart:core Object.noSuchMethod
Why this error occurs in tests?为什么在测试中会出现这个错误? And what is the right way to write tests for this class?
为这个 class 编写测试的正确方法是什么?
Problem solved.问题解决了。
Create of _isolate
and _isolateSendPort
is an async operation. _isolate
和_isolateSendPort
的创建是异步操作。 Thats why _isolateSendPort
was null on tests.这就是为什么
_isolateSendPort
在测试中是 null 的原因。 Call method _asyncInit()
from Mapper
constructor is wrong way to create an isolate.从
Mapper
构造函数调用方法_asyncInit()
是创建隔离的错误方法。
Here is working solution with lazy isolate initialization:这是具有延迟隔离初始化的工作解决方案:
class Mapper {
SendPort _isolateSendPort;
Isolate _isolate;
void _initIsolate() async {
final receivePort = ReceivePort();
_isolate = await Isolate.spawn(
_mappingFunction,
receivePort.sendPort,
);
_isolateSendPort = await receivePort.first;
}
...
Future<Output> map(Input input) async {
final port = ReceivePort();
if (_isolateSendPort == null) {
await _initIsolate();
}
_isolateSendPort.send(CrossIsolatesMessage<Input>(
sender: port.sendPort,
message: input,
));
return port.map((event) => event as Output).first;
}
...
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.