: Verifies that the browser will treat the response as an attachment with a specific filename.
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get; import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*; import static org.assertj.core.api.Assertions.assertThat; @WebMvcTest(FileController.class) class FileDownloadTest { @Autowired private MockMvc mockMvc; @MockBean private FileService fileService; @Test void shouldDownloadFileSuccessfully() throws Exception { // Arrange: Mock the service to return a dummy file byte[] content = "Hello, World!".getBytes(); when(fileService.loadFile("test.txt")).thenReturn(content); // Act & Assert: Execute GET and verify headers mockMvc.perform(get("/api/download/test.txt")) .andExpect(status().isOk()) .andExpect(header().string(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"test.txt\"")) .andExpect(content().contentType(MediaType.APPLICATION_OCTET_STREAM)) .andExpect(result -> { byte[] actualContent = result.getResponse().getContentAsByteArray(); assertThat(actualContent).isEqualTo(content); }); } } Use code with caution. 2. Testing URL-Based Downloads with HttpClient junit test for file download in java
If your code downloads a file from a remote URL (e.g., using java.net.http.HttpClient ), you should test that the local file is created correctly and contains the expected size. Example: Verifying Local File Creation : Verifies that the browser will treat the
: Use the @TempDir annotation in JUnit 5 to create sandbox environments for file downloads that are automatically cleaned up after the test. Testing URL-Based Downloads with HttpClient If your code
When writing these tests, focus on these critical metadata fields:
: Confirms the stream size matches the source data.