package capture import ( "fmt" "os" "testing" ) func TestOutputMergesStdoutAndStderr(t *testing.T) { got := Output(func() { fmt.Print("out") fmt.Fprint(stderrWriter(), "err") // write directly to stderr }) if got != "outerr" { t.Fatalf("unexpected combined output: %q", got) } } // stderrWriter returns the current process stderr; split for test clarity. func stderrWriter() *os.File { return os.Stderr }