Tesing: Sanity check

README.md

@@ -131,3 +131,40 @@ Let's add minimal interactivity to the page by introducing an input field and a
 </script>
 ```
 
+# Testing the Web Layer
+
+Let's test our simple app with JUnit. We will concentrate on using Spring Test and Spring Boot features to test the interactions between Spring and your code. 
+
+## Sanity check
+
+The first thing you can do is write a simple sanity check test that will fail if the application context cannot start.
+
+From `src/test/java/djmil/hellomvc/SmokeTest.java`
+
+```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 static org.assertj.core.api.Assertions.assertThat;
+
+@SpringBootTest
+public class SmokeTest {
+
+    @Autowired
+	private GreetingController controller;
+
+    @Test
+    void contextLoads() throws Exception {
+        assertThat(controller).isNotNull();
+    }
+}
+```
+
+The `@SpringBootTest` annotation tells Spring Boot to look for a main configuration class (one with `@SpringBootApplication`, for instance) and use that to start a Spring application context. You can run this test in your IDE or on the command line (by running `./mvnw test` or `./gradlew test`), and it should pass.
+
+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.|

src/test/java/djmil/hellomvc/SmokeTest.java

@@ -0,0 +1,19 @@
+package djmil.hellomvc;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@SpringBootTest
+public class SmokeTest {
+
+    @Autowired
+	private GreetingController controller;
+
+    @Test
+    void contextLoads() throws Exception {
+        assertThat(controller).isNotNull();
+    }
+}