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1.3.3 Testing the controller

Testing web applications can be tricky when making assertions against the content of an HTML page. Fortunately, Spring comes with some powerful test support that makes testing a web application easy.

For the purposes of the home page, you’ll write a test that’s comparable in complexity to the home page itself. Your test will perform an HTTP GET request for the root path / and expect a successful result where the view name is home and the resulting content contains the phrase “Welcome to….” The following code should do the trick.

Listing 1.6 A test for the home page controller

java

package tacos;

import static org.hamcrest.Matchers.containsString;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.view;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.test.web.servlet.MockMvc;

@WebMvcTest(HomeController.class)
public class HomeControllerTest {

  @Autowired
  private MockMvc mockMvc;

  @Test
  public void testHomePage() throws Exception {
    mockMvc.perform(get("/"))
      .andExpect(status().isOk())
      .andExpect(view().name("home"))
      .andExpect(content().string(
          containsString("Welcome to...")));
  }
}

The first thing you might notice about this test is that it differs slightly from the TacoCloudApplicationTests class with regard to the annotations applied to it. Instead of @SpringBootTest markup, HomeControllerTest is annotated with @WebMvcTest. This is a special test annotation provided by Spring Boot that arranges for the test to run in the context of a Spring MVC application. More specifically, in this case, it arranges for HomeController to be registered in Spring MVC so that you can send requests to it.

@WebMvcTest also sets up Spring support for testing Spring MVC. Although it could be made to start a server, mocking the mechanics of Spring MVC is sufficient for your purposes. The test class is injected with a MockMvc object for the test to drive the mockup.

The testHomePage() method defines the test you want to perform against the home page. It starts with the MockMvc object to perform an HTTP GET request for / (the root path). From that request, it sets the following expectations:

The response should have an HTTP 200 (OK) status.
The view should have a logical name of home.
The rendered view should contain the text “Welcome to….”

You can run the test in your IDE of choice or with Maven like this:

bash

$ mvnw test

If, after the MockMvc object performs the request, any of those expectations aren’t met, then the test will fail. But your controller and view template are written to satisfy those expectations, so the test should pass with flying colors — or at least with some shade of green indicating a passing test.

The controller has been written, the view template created, and you have a passing test. It seems that you’ve implemented the home page successfully. But even though the test passes, there’s something slightly more satisfying with seeing the results in a browser. After all, that’s how Taco Cloud customers are going to see it. Let’s build the application and run it.

1.3.3 Testing the controller ​

1.3.3 Testing the controller