How can I properly mock and verify static methods with arguments using `mockedStatic`?

General Discussions
,
1

Most examples for mockedStatic in Mockito cover methods without parameters:

mocked.when(Foo::method).thenReturn("bar");
assertEquals("bar", Foo.method());
mocked.verify(Foo::method);

I want to mock a static method that takes parameters, but this approach doesn’t work:

mocked.when(Foo.methodWithParams("SomeValue"));
2

When a static method has parameters, you need to wrap the call in a lambda to pass it to when(). For example:

try (MockedStatic<Foo> mocked = Mockito.mockStatic(Foo.class)) {
    mocked.when(() -> Foo.methodWithParams("SomeValue")).thenReturn("mockedValue");

    String result = Foo.methodWithParams("SomeValue");
    assertEquals("mockedValue", result);

    mocked.verify(() -> Foo.methodWithParams("SomeValue"));
}

The lambda ensures Mockito knows exactly which method call (with parameters) you want to mock. This approach worked smoothly in my projects.

3

If you want to mock a static method for any argument, you can combine the lambda with ArgumentMatchers:


import static org.mockito.ArgumentMatchers.anyString;

try (MockedStatic<Foo> mocked = Mockito.mockStatic(Foo.class)) {
    mocked.when(() -> Foo.methodWithParams(anyString())).thenReturn("mockedValue");

    assertEquals("mockedValue", Foo.methodWithParams("Hello"));
    assertEquals("mockedValue", Foo.methodWithParams("World"));
}

This is useful when you don’t care about the exact parameter value and just want the method mocked for all inputs.

4

Beyond mocking, verifying static method calls with arguments also uses a lambda:

try (MockedStatic<Foo> mocked = Mockito.mockStatic(Foo.class)) {
    mocked.when(() -> Foo.methodWithParams("Test")).thenReturn("mocked");

    Foo.methodWithParams("Test");

    mocked.verify(() -> Foo.methodWithParams("Test"));
}

I like this variation because it keeps mocking and verification consistent, and it avoids common pitfalls like forgetting to use a lambda for parameterized static methods.