Mocking Util class's static method using gmock

class SomeService{
  public String getValue(){
     return SomeUtil.generateValue();
  }
}

class SomeUtil{
   public static String generateValue() {
      return "yahoo";
   }
}

I want to unit test the SomeService.getValue method.

I am trying the following:

@Test
void "getValue should return whatever util gives"(){
    def mockSomeUtil = mock(SomeUtil)
    mockSomeUtil.static.generateValue().returns("blah")
    play {
        Assert.assertEquals(someService.getValue(), "blah")
    }
}

But it fails as the util method isn't actually getting mocked.

Question:

How can I unit test my service method?