{"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":1431,"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":1413,"sourceCodeEnd":1449,"githubUrl":"https://github.com/gofiber/fiber/blob/9a4c7e57fe0b080a04235d28a4b0d2b4b353d58c/app.go#L1413-L1449","documentation":"Returned by App.Test (app.go:1431) when conn.r.Write(dump) fails after DumpRequest succeeds — i.e. writing the serialized request bytes into the in-memory testConn. The testConn is an internal pipe; a write failure usually means the connection was already closed or the buffer rejected the bytes. It is rare and typically indicates the testConn was pre-closed or a prior operation tore down the pipe.","triggerScenarios":"Calling app.Test on a connection that has been closed, or reusing a test scenario where a previous Test closed the conn; very large dumped requests exceeding internal buffer limits under constrained conditions.","commonSituations":"Almost never seen in normal Test usage; surfaces in custom test harnesses that manipulate Fiber internals or in edge cases with huge request bodies.","solutions":["Ensure you pass a freshly built *http.Request per Test call and don't share/close internal state across tests.","Inspect the wrapped error — it is usually io.ErrClosedPipe or a write timeout.","Reduce the request body size if the dump is pathologically large."],"exampleFix":null,"handlingStrategy":"try-catch","validationCode":null,"typeGuard":null,"tryCatchPattern":"resp, err := app.Test(req)\nif err != nil {\n    if strings.Contains(err.Error(), \"failed to write\") {\n        // testConn write failed — usually a pre-closed pipe; build a fresh request/conn\n    }\n    return err\n}","preventionTips":["Pass a freshly built *http.Request per Test invocation; don't reuse closed state.","Inspect wrapped errors (often io.ErrClosedPipe) to confirm the cause.","Avoid pathologically large request bodies that stress the internal buffer."],"tags":["testing","http","connection","test-helper"],"analyzedSha":"9a4c7e57fe0b080a04235d28a4b0d2b4b353d58c","analyzedAt":"2026-08-04T21:44:03.395Z","schemaVersion":2}