How to achieve asynchronous task dependency with XCTestCases?

Question

I am writing some test cases for asynchronous operations where I have two operations on which unit test need to be performed.

Suppose I have some login webservice that need to called and on response of that another profile webservice should be called.

Is it possible to test above scenario using unit-testing in iOS?

Thank you in advance.

Answer 1

Yes it is actually quite easy, you use expectations to wait until a task(s) have been completed.

Example:

// Create an expectation for a background download task.
let expectation = XCTestExpectation(description: "Login and fetch profile")

MyApiClient.shared.login(username: username, password: password) { auth in

    // check login was successful before continuing
    MyApiClient.shared.fetchUserProfile(userId: auth.userId) { profile in 

        XCTAssertNotNil(profile)

        // Fulfill the expectation to indicate that the background task has finished successfully.
        expectation.fulfill()
    }
}

// Wait until the expectation is fulfilled, with a timeout of 10 seconds.
wait(for: [expectation], timeout: 10.0)