Tests Everywhere - Scala

rogervinas / tests-everywhere

🤠 Tests, Tests Everywhere!

Scala testing this simple Hello World with ScalaTest and Mockito

• Show me the code
  • Implementation
  • Test
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Show me the code

Implementation

1. Create HelloMessage class in HelloMessage.scala:

class HelloMessage:
  def text: String = "Hello World!"

We can create it as a class as Mockito is able to mock final classes.

1. Same way create HelloConsole class in HelloConsole.scala:

class HelloConsole:
  def print(text: String): Unit =
    println(text)

1. Create HelloApp class in HelloApp.scala:

class HelloApp(message: HelloMessage, console: HelloConsole):
  def printHello(): Unit =
    console.print(message.text)

1. Create main class in Main.scala that wraps it all together:

@main def main(): Unit =
  val message = HelloMessage()
  val console = HelloConsole()
  val app = HelloApp(message, console)
  app.printHello()

Test

Following ScalaTest > Writing your first test and ScalaTest + Mockito guides ...

1. Test HelloMessage in HelloMessageSpec.scala:

class HelloMessageSpec extends AnyFlatSpec {

  "A HelloMessage" should "return hello world" in {
    val message = HelloMessage()
    assertResult(message.text) {
      "Hello World!"
    }
  }
}

1. Test HelloApp in HelloAppSpec.scala:

class HelloAppSpec extends AnyFlatSpec {

  "A HelloApp" should "print hello message" in {
    val messageText = "Hello Test!"

    // 2.1 Create a mock of HelloMessage
    val message = mock[HelloMessage]
    // 2.2 Return "Hello Test!" whenever text is called
    when(message.text).thenReturn(messageText)

    // 2.3 Create a mock of HelloConsole
    val console = mock[HelloConsole]

    // 2.4 Create a HelloApp, the one we want to test, passing the mocks
    val app = HelloApp(message, 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)
  }
}

1. Test output should look like:

[info] HelloMessageSpec:
[info] A HelloMessage
[info] - should return hello world
[info] HelloAppSpec:
[info] A HelloApp
[info] - should print hello message
[info] Run completed in 515 milliseconds.
[info] Total number of tests run: 2
[info] Suites: completed 2, aborted 0
[info] Tests: succeeded 2, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.
[success] Total time: 6 s

Happy Testing! 💙