{"record":{"id":"bf8329e8709dbdca","repo":"gofiber/fiber","slug":"failed-to-write-w","errorCode":null,"errorMessage":"failed to write: %w","messagePattern":"failed to write: %w","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"app.go","lineNumber":1432,"sourceCode":"\t\t}\n\t}\n\n\t// Clear RequestURI so DumpRequest writes origin-form request line with\n\t// Host header instead of absolute-form URI without Host header.\n\treq.RequestURI = \"\"\n\n\t// Dump raw http request\n\tdump, err := httputil.DumpRequest(req, true)\n\tif err != nil {\n\t\treturn nil, fmt.Errorf(\"failed to dump request: %w\", err)\n\t}\n\n\t// Create test connection\n\tconn := new(testConn)\n\n\t// Write raw http request\n\tif _, err = conn.r.Write(dump); err != nil {\n\t\treturn nil, fmt.Errorf(\"failed to write: %w\", err)\n\t}\n\t// prepare the server for the start\n\tapp.startupProcess()\n\n\t// Serve conn to server\n\tchannel := make(chan error, 1)\n\tgo func() {\n\t\tvar returned bool\n\t\tdefer func() {\n\t\t\tif !returned {\n\t\t\t\tchannel <- ErrHandlerExited\n\t\t\t}\n\t\t}()\n\n\t\tchannel <- app.server.ServeConn(conn)\n\t\treturned = true\n\t}()\n","sourceCodeStart":1414,"sourceCodeEnd":1450,"githubUrl":"https://github.com/gofiber/fiber/blob/a105acad6c1e4576a77f01e02973f67e962bb58d/app.go#L1414-L1450","documentation":"After DumpRequest, the TestClient writes the dumped bytes into an in-memory testConn via conn.r.Write(dump). If that write fails (almost always indicates the dump is empty/oversized or the conn is in a bad state), the wrapped error is returned.","triggerScenarios":"Calling app.Test() with an extremely large request body, or in a test setup where the testConn has been closed/corrupted.","commonSituations":"Very large upload tests exceeding in-memory buffer limits; concurrent test runs sharing state; custom test harnesses reusing testConn incorrectly.","solutions":["Reduce test payload size, or test large bodies against a real started server with http.Client.","Inspect the wrapped error to identify the buffer/conn failure.","Run each app.Test() in isolation to rule out shared-state corruption."],"exampleFix":"// before\nbody := strings.Repeat(\"x\", 1<<30)\nresp, _ := app.Test(httptest.NewRequest(\"POST\", \"/\", strings.NewReader(body)))\n\n// after (use a real server for huge bodies)\nbody := strings.Repeat(\"x\", 1<<20)\nresp, _ := app.Test(httptest.NewRequest(\"POST\", \"/\", strings.NewReader(body)))","handlingStrategy":"validation","validationCode":"const maxTestBody = 1 << 20 // 1 MiB\nif req.ContentLength > maxTestBody {\n    return errors.New(\"use a real server for large bodies\")\n}","typeGuard":null,"tryCatchPattern":"if _, err := app.Test(req); err != nil {\n    return fmt.Errorf(\"test conn write failed: %w\", err)\n}","preventionTips":["Keep test payloads small; route huge bodies through a real server.","Run app.Test() in isolation to avoid shared-state issues.","Inspect wrapped errors before retrying."],"tags":["testing","http","test-client","buffer"],"backgroundTag":null,"analyzedSha":"a105acad6c1e4576a77f01e02973f67e962bb58d","analyzedAt":"2026-08-11T17:33:26.942Z","contentChangedAt":null,"schemaVersion":2},"datasetVersion":"2026-09-23T08:17:48.524Z"}