JerseyClientBuilderTest - Refactored

@Rule
public ExpectedException thrown = ExpectedException.none();

@Test
public void throwsAnExceptionWithoutAnEnvironmentAndOnlyAThreadPool() {
    thrown.expect(IllegalStateException.class);
    thrown.expectMessage("Must have either an environment or both an executor service and an object mapper");
    builder.using(executorService).build("test");
}