Mock Java static class from scala

Question

Any idea how from ScalaTest I can mock a static Java class??

I have this code

  val mockMapperComponent: IMapperComponent = mock[IMapperComponent]
  val applicationContext: ApplicationContext = mock[ApplicationContext]

  val appContextUtil: AppContextUtil = mock[AppContextUtil]


  override def beforeAll(): Unit = {
    mockStatic(classOf[AppContextUtil])
    when(AppContextUtil.getApplicationContext).thenReturn(applicationContext)
    when(applicationContext.getBean(classOf[IMapperComponent])).thenReturn(mockMapperComponent)

  }

In Java mockStatic with the annotation in the class @PrepareForTest({AppContextUtil.class}) do the trick, but from Scala I can only found in scalaTest documentation how to mock the normal access, but not static.

Regards.

Mezzotint

Have you looked at How do I mock static function (Object function, not class function) in scala? – Heavy

I’m afraid not yet. Seems like it’s not a very extended topic. At least not in mockito power mock – Mezzotint

Answer 1

Mocking Java static method in Scala is more involved than in Java because Mockito API use Java's ability to implicit cast a single-function interface to pointer of a function, for example: httpClientStaticMock.when(HttpClientBuilder::build).thenReturn(httpClientBuilder); notice function pointer usage: HttpClientBuilder::build.

As scala compiler does not have the same implicit casting rules, we have to de-sugar this call explicitly:

val httpClientStaticMock = mockStatic(classOf[org.apache.http.impl.client.HttpClientBuilder])
try {
  httpClientStaticMock.when(new org.mockito.MockedStatic.Verification {
    override def apply(): Unit = org.apache.http.impl.client.HttpClientBuilder.create()
  }).thenReturn(httpClientBuilder)

} finally {
  httpClientStaticMock.close()
}

Notice anonymous object usage to implement Verification interface: new org.mockito.MockedStatic.Verification.

Also, pay attention and do NOT forget to close static mocks in finally clause, otherwise very hard to troubleshoot errors will happen.

Augmenter

Can you explain what the block: new org.mockito.MockedStatic.Verification does? I'm trying to mock LocalDateTime.now and I don't get what I'm sopose to do inside the block – Ammoniacal

@MiguelSalas It calls a static function to be verified. In your case, it would be LocalDateTime.now and then in thenReturn you should provide mocking value. – Augmenter