使用相同的参数链接多个调用以返回不同的结果 [英] Chain multiple calls with same arguments to return different results

问题描述

我正在编写具有广泛单元测试范围的 Flutter 应用程序.
我正在使用 Mockito 来模拟我的类.
来自 Java ( Android )世界，在这里我可以使用 Mockito 链接调用以在后续调用中返回不同的值.
我希望这能奏效.

I'm in the process of writing a Flutter app with some extensive unit test coverage.
I'm using Mockito to mock my classes.
Coming from a Java (Android) world where I can use Mockito to chain calls to return different values on subsequent calls.
I would expect this to work.

import 'package:test/test.dart';
import 'package:mockito/mockito.dart';

void main() {
  test("some string test", () {
    StringProvider strProvider = MockStringProvider();
    when(strProvider.randomStr()).thenReturn("hello");
    when(strProvider.randomStr()).thenReturn("world");

    expect(strProvider.randomStr(), "hello");
    expect(strProvider.randomStr(), "world");
  });
}

class StringProvider {
  String randomStr() => "real implementation";
}

class MockStringProvider extends Mock implements StringProvider {}

但是它抛出:

Expected: 'hello'
Actual:   'world'
  Which: is different.

我发现唯一可行的工作方式就是跟踪自己.

The only working way I found that works is by keeping track myself.

void main() {
  test("some string test", () {
    StringProvider strProvider = MockStringProvider();

    var invocations = 0;
    when(strProvider.randomStr()).thenAnswer((_) {
      var a = '';
      if (invocations == 0) {
        a = 'hello';
      } else {
        a = 'world';
      }
      invocations++;
      return a;
    });

    expect(strProvider.randomStr(), "hello");
    expect(strProvider.randomStr(), "world");
  });
}

00:01 +1:所有测试都通过！

00:01 +1: All tests passed!

有更好的方法吗?

推荐答案

使用列表并使用 removeAt 返回答案:

Use a list and return the answers with removeAt:

import 'package:test/test.dart';
import 'package:mockito/mockito.dart';

void main() {
  test("some string test", () {
    StringProvider strProvider = MockStringProvider();
    var answers = ["hello", "world"];

    when(strProvider.randomStr()).thenAnswer((_) => answers.removeAt(0));

    expect(strProvider.randomStr(), "hello");
    expect(strProvider.randomStr(), "world");
  });
}

class StringProvider {
  String randomStr() => "real implementation";
}

class MockStringProvider extends Mock implements StringProvider {}

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