### Question:
CredHubCredentialsGenerator implements CredentialGenerator { @Override public Mono<Void> deleteString(String applicationId, String serviceInstanceId, String descriptor) { return credHubOperations.credentials() .deleteByName(new SimpleCredentialName(applicationId, serviceInstanceId, descriptor)); } CredHubCredentialsGenerator(ReactiveCredHubOperations credHubOperations); @Override Mono<Tuple2<String, String>> generateUser(String applicationId, String serviceInstanceId, String descriptor,
		int length, boolean includeUppercaseAlpha, boolean includeLowercaseAlpha, boolean includeNumeric,
		boolean includeSpecial); @Override Mono<String> generateString(String applicationId, String serviceInstanceId, String descriptor, int length,
		boolean includeUppercaseAlpha, boolean includeLowercaseAlpha, boolean includeNumeric,
		boolean includeSpecial); @Override Mono<Void> deleteUser(String applicationId, String serviceInstanceId, String descriptor); @Override Mono<Void> deleteString(String applicationId, String serviceInstanceId, String descriptor);  }### Answer:
@Test void deleteString() { given(this.credHubOperations.credentials()) .willReturn(credHubCredentialOperations); given(this.credHubCredentialOperations.deleteByName(any())) .willReturn(Mono.empty()); StepVerifier.create(generator.deleteString("foo", "bar", "hello")) .verifyComplete(); verify(credHubCredentialOperations).deleteByName(new SimpleCredentialName("foo", "bar", "hello")); verifyNoMoreInteractions(credHubOperations); verifyNoMoreInteractions(credHubCredentialOperations); }