如何在jasmine测试中模拟导出的typescript函数？ [英] How do I mock an exported typescript function in a jasmine test?

问题描述

我正在尝试在Jasmine测试中模拟从typescript文件导出的函数。我希望以下内容模拟导入的 foo 并返回条形码中的值1。

I'm trying to mock a function exported from a typescript file in a Jasmine test. I expect the following to mock the imported foo and return the value 1 in the spec for bar.

模拟似乎是不必要的，所以我显然遗漏了一些东西。我该如何修复这个例子？

The mock appears to be uncalled, so I'm clearly missing something. How can I fix this example?

demo.ts：

export function foo(input: any): any {
  return 2;
}

export function bar(input: any): any {
  return foo(input) + 2;
}

demo.ts.spec：

demo.ts.spec:

import * as demo from './demo';

describe('foo:', () => {
  it('returns 2', () => {
    const actual = demo.foo(1);
    expect(actual).toEqual(2);
  });
});

describe('bar:', () => {
  // let fooSpy;
  beforeEach(() => {
    spyOn(demo, 'foo' as any).and.returnValue(1); // 'as any' prevents compiler warning
  });

  it('verifies that foo was called', () => {
    const actual = demo.bar(1);
    expect(actual).toEqual(3); // mocked 1 + actual 2
    expect(demo.foo).toHaveBeenCalled();
  });
});

失败：

• 预期4等于3.


• 预期的间谍foo被调用。

推荐答案

杰弗瑞的回答帮助我走上正轨。

Jeffery's answer helped get me on the right track.

附加间谍附加到<$ c的右边参考$ c> foo 产品代码需要进行少量更改。 foo（）应该被称为 this.foo（）

To attach the spy is attached to the right reference for foo the product code needs to have a small change. foo() should be called as this.foo()

以下模式适用于测试（并且比我之前使用的复杂工作要清晰得多）。

The below pattern works for testing (and is a lot cleaner than the convoluted work around I was using previously).

demo.ts：

export function foo(input: any): any {
  return 2;
}

export function bar(input: any): any {
  return this.foo(input) + 2;
}

demo.ts.spec：

demo.ts.spec:

import * as demo from './demo';

describe('foo:', () => {
  it('returns 2', () => {
    const actual = demo.foo(1);
    expect(actual).toEqual(2);
  });
});

describe('bar:', () => {
  // let fooSpy;
  beforeEach(() => {
    spyOn(demo, 'foo' as any).and.returnValue(1);
  });

  it('verifies that foo was called', () => {
    const actual = demo.bar(1);
    expect(actual).toEqual(3);
    expect(demo.foo).toHaveBeenCalled();
  });
});

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