question: public final AssertSubscriber < T > assertError ( Class < ? extends Throwable > clazz ) { assertNotComplete ( ) ; int s = errors . size ( ) ; if ( s == 0 ) { throw new AssertionError ( "No error" , null ) ; } if ( s == 1 ) { Throwable e = errors . get ( 0 ) ; if ( ! clazz . isInstance ( e ) ) { throw new AssertionError ( "Error class incompatible: expected = " + clazz + ", actual = " + e , null ) ; } } if ( s > 1 ) { throw new AssertionError ( "Multiple errors: " + s , null ) ; } return this ; }
target:  Assert an error signal has been received.