Testing REST Clients with Spring WebClient and MockWebServer

Integrating third-party APIs is a core part of modern web development, but testing these integrations without relying on live external services can be challenging. This text-only course guides you through building reliable, non-blocking REST clients and testing their behavior under any network condition. You will learn how to handle successful responses, manage timeouts, and gracefully resolve API errors. By completing this course, you will be able to configure reactive HTTP clients and write deterministic unit tests that simulate real-world API behaviors without making actual network calls. What you'll learn: - Understand the fundamentals of reactive programming and the non-blocking architecture of Spring WebClient - Configure WebClient instances with custom headers, timeouts, and connection pools - Mock external API responses, HTTP headers, and status codes using MockWebServer - Practice testing edge cases, including slow network responses, rate limits, and server errors - Implement modern resilient patterns like retries and backoff strategies using built-in Spring features - Structure clean, maintainable integration tests that run quickly and reliably in your CI/CD pipelines This course begins with foundational concepts of HTTP clients and reactive streams, then moves step-by-step through practical configuration, mock testing, and advanced error handling. You will learn by reading detailed explanations and analyzing real-world Java code snippets. This course is designed for Java and Spring developers who want to improve their integration testing strategies. No prior experience with MockWebServer or reactive programming is required, though a basic understanding of Spring Boot is helpful. Start writing reliable, self-contained integration tests for your REST clients today.