@Test
public void shouldCallWithRequiredInt() throws IOException {

    when(requestMock.getMethod()).thenReturn("GET");
    when(requestMock.getPathInfo()).thenReturn("/goodbye");
    when(requestMock.getParameter("amount")).thenReturn("123");
    servlet.service(requestMock, responseMock);
    assertThat(amount).isEqualTo(123);
}