gistfile1.txt

@Test
public void fluxErrorHandling_onErrorReturn(){

    Flux<String> stringFlux = Flux.just("a","b","c")
            .concatWith(Flux.error(new RuntimeException("Exception Occurred")))
            .concatWith(Flux.just("D"))
            .onErrorReturn("default"); // here returning a simple string on any errors

    StepVerifier.create(stringFlux.log())
            .expectSubscription()
            .expectNext("a","b","c")
            .expectNext("default")
            .verifyComplete();
}