Use MockMvc for Spring web controller tests

This allows for easier error testing. Approach based on https://stackoverflow.com/questions/25901985/difference-between-mockmvc-and-resttemplate-in-integration-tests

Author: James Little

src/main/java/com/bnc/sbjb/rest/Controller.java

@@ -9,9 +9,15 @@
 @RequestMapping("${resource.path}")
 public class Controller {
 
+    @RequestMapping("/hello-error")
+    @ResponseStatus(HttpStatus.OK)
+    public String notYetWorld() {
+        throw new IllegalStateException("Hello World");
+    }
+
     @RequestMapping("/hello")
     @ResponseStatus(HttpStatus.OK)
     public String helloWorld() {
-        throw new IllegalStateException("Hello World");
+        return "Hello World";
     }
 }

src/test/java/com/bnc/sbjb/rest/ControllerTest.java

@@ -1,29 +1,42 @@
 package com.bnc.sbjb.rest;
 
-import static org.assertj.core.api.Assertions.assertThat;
+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 org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
-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.boot.test.autoconfigure.web.servlet.WebMvcTest;
 import org.springframework.test.context.junit.jupiter.SpringExtension;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.ResultMatcher;
 
-@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
 @ExtendWith(SpringExtension.class)
-public class ControllerTest {
+@WebMvcTest(Controller.class)
+class ControllerTest {
 
     @Value("${resource.path}")
     private String basePath;
 
     @Autowired
-    private TestRestTemplate template;
+    private MockMvc mockMvc;
+
+    private ResultMatcher equals(String string) {
+        return content().string(string);
+    }
+
+    @Test
+    @DisplayName("Spring says hello world")
+    void testHelloWorld() throws Exception {
+        mockMvc.perform(get(basePath + "/hello")).andExpect(equals("Hello World"));
+    }
 
     @Test
-    void testHelloWorld() {
-        String actual = template.getForObject(basePath + "/hello", String.class);
-        assertThat(actual).isEqualTo("Hello World");
+    @DisplayName("Spring handles errors gracefully")
+    void testNotYetWorld() throws Exception {
+        mockMvc.perform(get(basePath + "/hello-error")).andExpect(status().is5xxServerError());
     }
 }