I’m working with a Scala 2 project. I have the following code:

package com.myproject.commands;

object MyCommand {

  def execute(args: Map[String, String]) = {
    //do some validations...
    doRealStuff(args)
  }

  private[commands] def doRealStuff(args: Map[String, String]) = {
    //real process...
  }
}

Due to technical restrictions I cannot change the object design to class because it involves a refactor of the whole project, test re-definitions and exhaustive functional and regression testing so it’s not feasible for the time being.

I have to add some behavior that must run always at the end of the execute command, no matter if doRealStuff failed. I came up with a try/catch:

package com.myproject.commands;

object MyCommand {

  def execute(args: Map[String, String]) = {
    var exception: Option[Throwable] = None
    //do some validations...
    try {
      doRealStuff(args)
    } catch (e) {
      exception = Some(e)
      //handle exception...
    } finally {
      finalSteps(args, exception)
    }
  }

  private[commands] def doRealStuff(args: Map[String, String]) = {
    //real process...
  }

  private def finalSteps(args: Map[String, String], exception: Option[Throwable) = {
    //add exception data if exists
  }
}

This works when making doRealStuff method failing using a debugger and tweaking some variables or running another process that will make it fail. And on a testing env can also cover this case. But I’m required to add a unit test in our code to check this path. This means I need to mock the companion object MyCommand. I tried using PowerMockito but hit a road block:

package com.myproject.commands;

@RunWith(classOf[PowerMockRunner])
@PrepareForTest(Array(classOf[MyCommand.type]))
class MyCommandSpec extends AnyFlatSpec with Matchers with MockitoSugar {

  @Rule
  def rule = new PowerMockRule()

  "MyCommand" must "fail on doRealStuff" in {
    // Arrange
    PowerMockito.mockStatic(MyCommand.getClass)

    when(MyCommand.doRealStuff(any())).thenThrow(new Exception("test"))

    // Act
    val thrown = the[Throwable] thrownBy MyCommand.execute(/* args... */)

    // Assert
    thrown mustBe a[Exception]
  }
}

This fails here:

@PrepareForTest(Array(classOf[MyCommand.type]))

With compiler error message:

class type required but com.myproject.commands.MyCommand.type found

And if I change it to get the class as in the “Arrange” section

@PrepareForTest(Array(MyCommand.getClass))

I get this other error:

annotation argument needs to be a constant; found: MyCommand.getClass()

How can I solve this?

By the way, this is the definition of @PrepareForTest from PowerMock (it’s in Java, just putting the relevant part)

public @interface PrepareForTest {
    Class<?>[] value() default IndicateReloadClass.class;
}