Using InjectMock on Object with private static final fields failing

I am writing test cases for a legacy code which for some reason we dont want to change. The code is something like this

 public class ToBeTested{
    private static final String field1=SomeUtil.getProperty("somekey");        
    @AutoWired
    Someservice service;
 }

In my Junit I am using powermock with mockito and did something like this

public class myTestClass{
      @Mock
      SomeService service;
      @InjectMock
      ToBeTested tested;
}

However, InjectMocks fails to create the object for ToBeTested since the final fields are not provided

So I implemented a @BeforeClass and mocked the static method of SomeUtil. This works if i have only one test case. But for more than one test case, only one passes and others are failing with same error that

cannot instantiate @injectmocks field named you haven't provided the instance at field declaration

I have been able to resolve this by using something as below:

public class myTestClass{
          @Mock
          SomeService service;

          ToBeTested tested;

    @Before
    public void setup(){
        MockitoAnnotations.initMocks(this);
        mockStatic(SomeUtil.class);
        when(SomeUtil.getProperty(anyString())).thenReturn("test");
        toBeTested=new ToBeTested();    Whitebox.setInternalState(toBeTested,"someService",someService);
    }
    }

However am not a fan of using reflection in Junit which WhiteBox does internally. Is there a better way to do this?