Mockito can mock static methods!

11 Jul 2020

Hot news!

Mockito just released version 3.4.0 which can now mock static methods.

Before 3.4.0, Mockito could not mock static methods. It could only mock non-static methods. Though, PowerMock could. But PowerMock did it slowly: it replaced a classloader for every test, and executed the whole test within this classloader.

And the new Mockito 3.4.0 way should be more effective because it has narrower scope: it mock the static method only within one small lambda. Graceful.

Let’s try it!

Step 1: dependency

In your build.gradle replace mockito-core:3.3.3 by mockito-inline:3.4.0:

testImplementation('org.mockito:mockito-inline:3.4.0')

Step 2: what are we going to mock

Let’s assume we have a class with static method (that we want to mock in test):

class Buddy {
  static String name() {
    return "John";
  }
}

Step 3: Mock the static method

We can use new method Mockito.mockStatic() for this:

@Test
void lookMomICanMockStaticMethods() {
  assertThat(Buddy.name()).isEqualTo("John");

  try (MockedStatic<Buddy> theMock = Mockito.mockStatic(Buddy.class)) {
    theMock.when(Buddy::name).thenReturn("Rafael");
    assertThat(Buddy.name()).isEqualTo("Rafael");
  }

  assertThat(Buddy.name()).isEqualTo("John");
}