如何模拟两次开玩笑的函数

Question

我需要为在一个函数中被调用两次的函数编写一个测试用例。

async getAssets ( skuId, commonSku) {
    const { items } = await this.getMediaSet( skuId ); 
    const { items: commonSkuItems } = commonSku ? await this.getMediaSet( commonSku ) : { items: []}; 
    return [ ...items, ...commonSkuItems ];
 }

getMediaSet 方法返回的是一个特定于 skuId 的数据对象，如下所示

  const response =  {

  "items": [
    {
     "type": "img",
     "src": "https://media/25131",
     "width": 2000,
     "height": 2000,
     "format": "PNG",
     "opaque": "false"
   },
   {
    "type": "img",
    "src": "https://media/23232",
    "width": 2000,
    "height": 2000,
    "format": "PNG",
    "opaque": "false"
   }
 ]
}

我尝试测试的方式如下所示

  const result =  {

  "items": [
    {
     "type": "img",
     "src": "https://media/25131",
     "width": 2000,
     "height": 2000,
     "format": "PNG",
     "opaque": "false"
   },
   {
    "type": "img",
    "src": "https://media/23232",
    "width": 2000,
    "height": 2000,
    "format": "PNG",
    "opaque": "false"
   }
 ]
}

      const getMediaSet = jest.fn().mockImplementation( () => Promise.resolve( {response} ) );
 
  
  let output = await getAssets( '251', '253' );
  expect( output ).toMatchObject( result );

问题是如何模拟 getMediaSet twice ？ 因为我的另一个调用未定义。

Answer 1

所以，我找到了答案。我们需要像这样更改函数模拟实现

   cmsDataSource.getMediaSet = jest
    .fn()
    .mockReturnValue( response ) // Response in first call
    .mockReturnValueOnce( response ) // Response in second call

代替

 const getMediaSet = jest.fn().mockImplementation( () => Promise.resolve( {response} ) );