如何使用Jest测试动态导入然后捕捉

问题描述

因此，我一直在努力如何总体上测试动态导入，在这种情况下，尤其是在开玩笑的情况下，我在互联网上阅读了很多书，但没有发现任何具体内容，因此我考虑将问题集中起来体面的解决方案。

我在类中有以下方法

class MyClass {
   successMethod() {  ...  }

   errorMethod() { ... }

    myMethod() {
        return import('./myFile.js')
           .then(() => this.successMethod())
           .catch(() => this.errorMethod());
    }
}

我的问题是：

您如何使用Jest来模拟此动态导入的成功和失败承诺情况，以确保分别解决或失败时调用每种方法（successMethod和errorMethod）？

我发现jest.doMock有助于模拟已解决的案例，但没有找到一种通过模拟动态加载失败的方法，因此没有发现catch案例。

注意：这不是React应用，这是Vanilla JS项目。

解决方法

原型方法可以在MyClass.prototype或类实例上进行监视或模拟。应该为每个测试恢复模块模拟和间谍功能，以使它们彼此不受影响。

let myClass;
beforeEach(() => {
  jest.resetModules();
  jest.restoreAllMocks();
  myClass = new MyClass();
  jest.spyOn(myClass,'successMethod');
  jest.spyOn(myClass,'errorMethod');
});

jest.doMock需要在调用后导入所有受影响的模块。为了使动态import导致拒绝承诺，myFile模块在​​评估时应该抛出错误。由于动态import返回一个Promise，因此测试应该是异步的。

it('...',async () => {
  jest.mock('./myFile.js',() => 'value');
  await expect(myClass.myMethod()).resolves.toEqual(/* return value from successMethod */);
  expect(myClass.successMethod).toBeCalled();
  expect(myClass.errorMethod).not.toBeCalled();
});

it('...',() => { throw new Error() });
  await expect(myClass.myMethod()).rejects.toThrow(/* error message from errorMethod */);
  expect(myClass.successMethod).not.toBeCalled();
  expect(myClass.errorMethod).toBeCalled();
});

,

也许像

faizrahman@138-38-186-80 ~ % sudo pip install matplotlib
Password:
DEPRECATION: Python 2.7 reached the end of its life on January 1st,2020. Please upgrade your Python as Python 2.7 is no longer maintained. pip 21.0 will drop support for Python 2.7 in January 2021. More details about Python 2 support in pip can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support pip 21.0 will remove support for this functionality.
WARNING: The directory '/Users/faizrahman/Library/Caches/pip' or its parent directory is not owned or is not writable by the current user. The cache has been disabled. Check the permissions and owner of that directory. If executing pip with sudo,you may want sudo's -H flag.
Requirement already satisfied: matplotlib in /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python (1.3.1)
Requirement already satisfied: numpy>=1.5 in /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python (from matplotlib) (1.8.0rc1)
Requirement already satisfied: python-dateutil in /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python (from matplotlib) (1.5)
Requirement already satisfied: tornado in /Library/Python/2.7/site-packages (from matplotlib) (5.1.1)
Requirement already satisfied: pyparsing>=1.5.6 in /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python (from matplotlib) (2.0.1)
Requirement already satisfied: nose in /Library/Python/2.7/site-packages (from matplotlib) (1.3.7)
Requirement already satisfied: singledispatch in /Library/Python/2.7/site-packages (from tornado->matplotlib) (3.4.0.3)
Requirement already satisfied: futures in /Library/Python/2.7/site-packages (from tornado->matplotlib) (3.3.0)
Requirement already satisfied: backports-abc>=0.4 in /Library/Python/2.7/site-packages (from tornado->matplotlib) (0.5)
Requirement already satisfied: six in /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python (from singledispatch->tornado->matplotlib) (1.12.0)
faizrahman@138-38-186-80 ~ %