@Test
    public void trouble_maker() {
        Mono<String> trouble = null; //todo: change this line
        StepVerifier.create(trouble)
                    .expectError(IllegalStateException.class)
                    .verify();
    }
@Test
    public void trouble_maker() {
        Mono<String> trouble = null;
        StepVerifier.create(trouble)
                    .expectError(IllegalStateException.class)
                    .verify();
    }
@test public void trouble_maker() { mono<string> trouble = null; stepverifier.create(trouble) .expecterror(illegalstateexception.class) .verify(); }