Spring WebFlux Testing

Signals: @WebFluxTest, WebTestClient, StepVerifier, Mono, Flux, mutateWith, mockUser(), mockJwt(), thenCancel, verifyComplete, withVirtualTime

Tested With

• Spring Boot 3.2+ / Spring Boot 4.x
• Spring Framework 6.x / Spring Framework 7.x
• Reactor Core 3.5+ / 3.7+
• Spring Security 6.x / 7.x (auto-configured in @WebFluxTest)
• JUnit 5

Do NOT Use This Skill When

• Testing Spring MVC (servlet-based) controllers → use spring-mvc-testing
• Testing Spring Security rules in a servlet-based application → use spring-security-testing
• Testing JPA repositories → use spring-jpa-testing
• Testing WebSocket or STOMP messaging → use spring-websocket-testing
• Writing pure unit tests for reactive service logic → use spring-testing-fundamentals for AssertJ/Mockito patterns, combine with StepVerifier for reactive