在 ecmascript 中模拟静态方法

Question

I have a static class which is used in another class. To make a unit test, I need to mock that class but HOW?

import {StaticClass} from '';

class UserClass {
  method() {
    StaticClass.staticMethod();
  }
}


it('should call staticMethod', () => {
  new UserClass().method();
  expect(StaticClass.staticMethod).toHaveBeenCalled();
})

Answer 1

You should use a stub/mock library such as sinonjs .

Eg

user.js :

import { StaticClass } from './static';

export class UserClass {
  method() {
    StaticClass.staticMethod();
  }
}

static.js :

export class StaticClass {
  static staticMethod() {
    console.log('staticMethod implementation');
  }
}

user.test.js :

import { UserClass } from './user';
import sinon from 'sinon';
import { StaticClass } from './static';

describe('64135983', () => {
  it('should pass', () => {
    const staticMethodStub = sinon.stub(StaticClass, 'staticMethod');
    new UserClass().method();
    sinon.assert.calledOnce(staticMethodStub);
    staticMethodStub.restore();
  });
});

unit test result:

  64135983
    ✓ should pass


  1 passing (10ms)

-----------|---------|----------|---------|---------|-------------------
File       | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
-----------|---------|----------|---------|---------|-------------------
All files  |      80 |      100 |      50 |      80 |                   
 static.ts |      50 |      100 |       0 |      50 | 3                 
 user.ts   |     100 |      100 |     100 |     100 |                   
-----------|---------|----------|---------|---------|-------------------

Answer 2

Easily, I could use spyOn method to check whether my method has been called.

spyOn(StaticClass, 'staticMethod').and.returnValue('mock value');

Also I need to use expect to check whether it has been called

expect(StaticClass.staticMethod).toHaveBeenCalled();