Sometimes, we want to check that an argument to a mocked function is a function with Jest.

In this article, we’ll look at how to check that an argument to a mocked function is a function with Jest.

How to check that an argument to a mocked function is a function with Jest?

To check that an argument to a mocked function is a function with Jest, we can use the toBeCalledWith method.

For instance, we write

expect(AP.require).toBeCalledWith('messages', expect.any(Function))

to check that AP.require is called with 'messages' and a function respectively.

expect.any(Function) checks that the argument of AP.require is a function.

Conclusion

To check that an argument to a mocked function is a function with Jest, we can use the toBeCalledWith method.