    @Test
    public void testOnAddedHeader() throws InterruptedException {

        PokeDataSource dataSource = new PokeDataSource(pokemonService);

        TestObserver<String> observer = new TestObserver<>();
        dataSource.getPokemonStringObservable("12").subscribe(observer);

        RecordedRequest recordedRequest = getMockWebServer().takeRequest();

        assertEquals("application/json", recordedRequest.getHeader("Content-Type"));

    }