在打字稿测试中用玩笑模拟从另一个文件调用的函数

Question

I have a function processCosts in prepareStatement.ts . processCosts calls a function, calculatePrice imported from coreLogic.ts .

I have a test file reports.integration.ts which imports processCosts but I want to mock calculatePrice , which is the function processCosts calls. I created a file coreLogic.ts under my __mocks__ folder with the content:

export const calculatePrice = jest.fn(() => {});

and then in my test file, outside my test's it(...) , but inside the describe(...) I wrote

jest.mock('../statements/prepareStatement');

Finally, the test itself:

it('should calculate processCost and 4 x what calculatePrice returns', async () => {
    (calculatePrice as jest.Mock).mockImplementationOnce(() => 100.00);
    expect(processCost).to.equal(400.00); // processCost will do 4*whatever calculatePrice is
}

When I run my code I get

TypeError: coreLogic_1.calculatePrice.mockImplementationOnce is not a function

Can someone point out where I've gone wrong? The people who have done something similar to what I have done are calling the method they mock in their test as opposed to inside another imported function. Regardless, after attaching a debugger, my code baulks on this line:

(calculatePrice as jest.Mock).mockImplementationOnce(() => 100.00);

Answer 1

this is what fixed it. I moved the jest.mock(...) outside the describe(...) and it(...) to the top level of the file and everything started working.