Tests Everywhere - Swift

Published at

12/18/2023

rogervinas / tests-everywhere

🤠 Tests, Tests Everywhere!

Swift testing this simple Hello World with XCTest and Cuckoo

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- Implementation
- Test
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Implementation

Sorry but reading that constant and variable names can contain almost any character, including Unicode characters I could not resist 😅 ...

1) Create HelloMessage class in HelloMessage.swift:

class HelloMessage {
  var 👋: String {
    get {
      return "Hello World!"
    }
  }
}

2) Same way create HelloConsole class in HelloConsole.swift:

class HelloConsole {
  func print(👋: String) {
    Swift.print(👋)
  }
}

3) Create HelloApp class in HelloApp.swift:

class HelloApp {

  let message: HelloMessage
  let console: HelloConsole

  init(message: HelloMessage, console: HelloConsole) {
    self.message = message
    self.console = console
  }

  func printHello() {
    console.print(👋: message.👋)
  }
}

4) Create main class in Main.swift that wraps it all together:

@main
public struct Main {
  public static func main() {
    let message = HelloMessage()
    let console = HelloConsole()
    let app = HelloApp(message: message, console: console)
    app.printHello()
  }
}

Test

Following XCTest and Cuckoo guides ...

1) Mock generation

Mocks have to be generated statically, you can follow these instructions or alternatively:

Build generator (only once, XCode command line tools required):

git clone [email protected]:Brightify/Cuckoo.git /tmp/Cuckoo
/tmp/Cuckoo/build_generator

Generate mocks (as many times as needed):

/tmp/Cuckoo/Generator/bin/cuckoo_generator generate \
  --testable Hello \
  --output Tests/Mocks.swift \
  Sources/HelloMessage.swift \
  Sources/HelloConsole.swift

You can also integrate mocks generation in the build, before compile phase.

2) Test HelloMessage in HelloMessageTest.swift:

final class HelloMessageTest: XCTestCase {
  func testHelloMessageShouldReturnHelloWorld() throws {
    let message = HelloMessage()
    XCTAssertEqual(message.👋, "Hello World!")
  }
}

3) Test HelloApp in HelloAppTest.swift:

final class HelloAppTest: XCTestCase {
  func testHelloAppShouldDisplayHelloMessage() throws {
    let messageText = "Hello Test!"
    // 2.1 Create a mock of HelloMessage
    let message = MockHelloMessage()
    // 2.2 Return "Hello Test!" whenever 👋 getter is called
    stub(message) { stub in
      when(stub.👋.get).thenReturn(messageText)
    }

    // 2.2 Create a mock of HelloConsole
    let console = MockHelloConsole()
    // 2.3 Do nothing whenever print is called
    stub(console) { stub in
      when(stub.print(👋: anyString())).thenDoNothing()
    }

    // 2.4 Create a HelloApp, the one we want to test, passing the mocks
    let app = HelloApp(message: message, console: console)
    // 2.5 Execute the method we want to test
    app.printHello()

    // 2.6 Verify HelloConsole mock print() method
    // has been called once with "Hello Test!"
    verify(console).print(👋: messageText)
  }
}

4) Test output should look like:

Test Suite 'All tests' started at 2023-12-12 16:48:21.225
Test Suite 'debug.xctest' started at 2023-12-12 16:48:21.227
Test Suite 'HelloAppTest' started at 2023-12-12 16:48:21.227
Test Case 'HelloAppTest.testHelloAppShouldDisplayHelloMessage' started at 2023-12-12 16:48:21.227
Test Case 'HelloAppTest.testHelloAppShouldDisplayHelloMessage' passed (0.003 seconds)
Test Suite 'HelloAppTest' passed at 2023-12-12 16:48:21.230
    Executed 1 test, with 0 failures (0 unexpected) in 0.003 (0.003) seconds
Test Suite 'HelloMessageTest' started at 2023-12-12 16:48:21.230
Test Case 'HelloMessageTest.testHelloMessageShouldReturnHelloWorld' started at 2023-12-12 16:48:21.231
Test Case 'HelloMessageTest.testHelloMessageShouldReturnHelloWorld' passed (0.001 seconds)
Test Suite 'HelloMessageTest' passed at 2023-12-12 16:48:21.232
    Executed 1 test, with 0 failures (0 unexpected) in 0.001 (0.001) seconds
Test Suite 'debug.xctest' passed at 2023-12-12 16:48:21.232
    Executed 2 tests, with 0 failures (0 unexpected) in 0.004 (0.004) seconds
Test Suite 'All tests' passed at 2023-12-12 16:48:21.232
    Executed 2 tests, with 0 failures (0 unexpected) in 0.004 (0.004) seconds

Happy Testing! 💙