How to call a function in Jest with a specific value?-CodePudding

I have a function in my application which returns a true or false by checking a second function. And this function will disable/enable the input field.

Now I want to spy on the first function and call this with a specific value.

I know that this is possible in Jasmine with spyOn and .and.returnValue. And with that I can cover the different cases for when the function returns a true or false.

How can I call a function in Jest with a specific value?

My code:

<input
 :id="id"
 v-model="searchKey"
 :disabled="testFunctionB"
 type="text"
 name="search box"
 autocomplete="off"
>   

computed: {
    testFunctionA () {
      if(!this.testData) return false 
      return this.testData1 !== ''
    },
    testFunctionB () {
      if (this.testData2 === false) return false
      return this.testFunctionA
    }
}

So I want to cover the function when testData2 is defined as null, this means that testFunctionB will return testFunctionA.

I want to make sure that the function testFunctionA is true and that testFunctionB also returns true. So I can cover the multiple cases.

This is what I tried:

it('should disable the input when the testData2 value is not defined and the testFunctionA is true', async () => {
        await wrapper.setProps({testData2: null})
        wrapper.vm.testFunctionA = jest.fn()
        wrapper.vm.testFunctionA.mockReturnValueOnce(true)

        expect(wrapper.vm.testFunctionB).toBe(true)
})

So I try to put a spy on testFunctionA and return a true or false. How can I do this?

CodePudding user response：

In order to cover your test case, you need to mock testFunctionA before you call setProps({testData2: null}). That's because wrapper.setProps(...) is what triggers the evaluation of testFunctionB:

it('should disable the input when the testData2 value is not defined and the testFunctionA is true', async () => {
 jest.spyOn(wrapper.vm, 'testFunctionA').mockReturnValueOnce(true);
 await wrapper.setProps({testData2: null});
 expect(wrapper.vm.testFunctionB).toBe(true);
})