iOS Unit Testing by Example

Write Your First Assertion

Now that we have a home for tests, let’s go over how to use the testing mechanism. How does a test communicate success or failure? What does Xcode show you when a test fails? What does it show when a test succeeds?

The way a test reports a failure to XCTest is through assertions. Let’s start with the simplest assertion. Add the following method to the AssertYourselfTests class:

AssertYourself/AssertYourselfTests/AssertYourselfTests.swift

func test_fail() {
    XCTFail()
}

First, what makes this function a test?

• It lives within a subclass of XCTestCase.
• It isn’t declared private.
• Its name starts with test.
• It takes no parameters.
• It has no return value.

Why the underscore in the test name? This goes ...