Testing: Http requests

README.md

@@ -167,4 +167,40 @@ The `@SpringBootTest` annotation tells Spring Boot to look for a main configurat
 
 Spring interprets the `@Autowired` annotation, and the controller is injected before the test methods are run. We use [AssertJ](http://joel-costigliola.github.io/assertj/) (which provides `assertThat()` and other methods) to express the test assertions.
 
-> A nice feature of the Spring Test support is that the application context is cached between tests. That way, if you have multiple methods in a test case or multiple test cases with the same configuration, they incur the cost of starting the application only once. You can control the cache by using the @DirtiesContext annotation.|
+> A nice feature of the Spring Test support is that the application context is cached between tests. That way, if you have multiple methods in a test case or multiple test cases with the same configuration, they incur the cost of starting the application only once. You can control the cache by using the @DirtiesContext annotation.
+
+## Test HTTP requests
+
+It is nice to have a sanity check, but you should also write some tests that assert the behavior of your application. To do that, you could start the application and listen for a connection (as it would do in production) and then send an HTTP request and assert the response. The following listing (from `src/test/java/djmil/hellomvc/HttpRequestTest.java`) shows how to do so:
+
+```java
+package djmil.hellomvc;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.beans.factory.annotation.Value;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+public class HttpRequestTest {
+
+	@Value(value="${local.server.port}")
+	private int port;
+
+	@Autowired
+	private TestRestTemplate restTemplate;
+
+	@Test
+	public void greetingShouldReturnDefaultMessage() throws Exception {
+		assertThat(this.restTemplate.getForObject("http://localhost:" + port + "/greeting",
+				String.class)).contains("Hello, World");
+	}
+}
+```
+
+Note the use of `webEnvironment=RANDOM_PORT` to start the server with a random port (useful to avoid conflicts in test environments) and the injection of the port with `@LocalServerPort`. Also, note that Spring Boot has automatically provided a `TestRestTemplate` for you. All you have to do is add `@Autowired` to it.

src/test/java/djmil/hellomvc/HttpRequestTest.java

@@ -0,0 +1,27 @@
+package djmil.hellomvc;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.test.web.client.TestRestTemplate;
+import org.springframework.beans.factory.annotation.Value;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+public class HttpRequestTest {
+
+	@Value(value="${local.server.port}")
+	private int port;
+
+	@Autowired
+	private TestRestTemplate restTemplate;
+
+	@Test
+	public void greetingShouldReturnDefaultMessage() throws Exception {
+		assertThat(this.restTemplate.getForObject("http://localhost:" + port + "/greeting",
+				String.class)).contains("Hello, World");
+	}
+}