How to create unit tests with MockMvc for your REST controller - spring-boot

Question

I have a REST controller and I want to create Unit tests for my controller and I'm not interested in loading the spring context.
Having a spring-boot application, the requirement is to use junit5 and MockMvc.

Answer 1

Here is a working example with MockMvc, creating simple unit tests for the REST controller.
Here is the Dictionary REST controller.
#Slf4j
#RequiredArgsConstructor
#RestController
#RequestMapping(DICTIONARY_ENDPOINT_URL)
public class DictionaryController {
protected static final String DICTIONARY_ENDPOINT_URL = "/dictionaries";
private final DictionaryService dictionaryService;
#GetMapping(value = "download", produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
public ResponseEntity<byte[]> downloadDictionariesFile() throws FileNotFoundException {
log.info("Called download dictionaries file endpoint.");
final String fileRelativePath = dictionaryService.getDictionariesFileRelativePath();
return ResponseEntity.ok()
.header("Content-Disposition", "attachment; filename=" + getDictionariesFileByRelativePath(fileRelativePath))
.body(dictionaryService.getDictionaryFileContent(fileRelativePath));
}
}
Here is the DictionaryControllerTest
package <...>;
import <...>.DictionaryService;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;
import java.io.FileNotFoundException;
import static org.hamcrest.Matchers.containsString;
import static org.mockito.ArgumentMatchers.anyString;
import static org.mockito.Mockito.*;
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;
#ExtendWith(MockitoExtension.class)
class DictionaryControllerTest {
private String dictionaryFilePath = "<<path to the file>>";
private String dictionaryFileContent = "<<content here>>";
private String errorMessage = "Dictionary file, does not exists!";
private String endpointUrl = "/dictionaries/download";
#Mock
private DictionaryService dictionaryService;
#InjectMocks
private DictionaryController dictionaryController;
private MockMvc mockMvc;
#BeforeEach
public void setUp() {
mockMvc = MockMvcBuilders.standaloneSetup(dictionaryController).build();
}
#Test
#DisplayName("Should return response with content file")
void downloadDictionariesFile_validRequest_success() throws Exception {
when(dictionaryService.getDictionariesFileRelativePath())
.thenReturn(dictionaryFilePath);
when(dictionaryService.getDictionaryFileContent(anyString()))
.thenReturn(dictionaryFileContent.getBytes());
mockMvc.perform(get(endpointUrl))
.andExpect(status().isOk())
.andExpect(content().string(containsString(dictionaryFileContent)));
verify(dictionaryService).getDictionariesFileRelativePath();
verify(dictionaryService).getDictionaryFileContent(any());
}
}
Here are a few lines of my pom.xml file
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.4.1</version>
<relativePath/>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</dependency>
</dependencies>