ViewModels per Unit-Test testen

Your ViewModel holds the logic, so it is the perfect place to test. You can check behavior without ever launching the full UI. 🧪

Because a ViewModel is a plain class, you can create one in a test and call its methods directly. This keeps your tests fast and focused.

Apple's testing framework is XCTest. You import it and write test classes that Xcode runs for you with a single keystroke.

A XCTestCase subclass groups related tests. Every test method name must start with the word test so Xcode discovers it automatically.

A clean test follows three steps: arrange the objects, act by calling a method, then assert the result is what you expected.

Start by making a fresh instance of the ViewModel inside your test. A new object per test keeps each one independent and reliable.

Now act on it. Call the method you want to verify, just like your view would when a button is tapped. ➡️

Use XCTAssertEqual to confirm a value matches what you expect. If it differs, the test fails with a clear message.

For true or false results, reach for XCTAssertTrue and XCTAssertFalse. They read clearly and document your intent.

Good tests cover more than the happy path. Check empty input, limits, and unexpected values so bugs surface before your users do.

Press Command-U in Xcode to run every test. Green checkmarks mean your logic still works after each change you make.

You learned to test a ViewModel in isolation: create it, call a method, then assert the result with XCTest. Fast, focused, dependable. 🎉