@Test
public void shouldGive400OnParameterConversion() throws IOException {

    FakeServletRequest request = new FakeServletRequest("GET", contextRoot, "/api", "/goodbye");
    request.setParameter("amount", "one");
    servlet.service(request, response);
    assertThat(response.getStatus()).isEqualTo(400);
    assertThat(response.getStatusMessage()).isEqualTo("Could not convert amount=one to int");
}