.

go/internal/xtracing/tracetest/example_test.go

@@ -183,16 +183,18 @@ func verifyInSubprocess(t *testing.T, f func(t *testing.T), targvExtra ...string
 	argv = append(argv, targvExtra...)
 	cmd := exec.Command(os.Args[0], argv...)
 	cmd.Env = append(os.Environ(), "TRACETEST_EX_VERIFY_IN_SUBPROCESS=1")
-	bout, err := cmd.CombinedOutput()
-	out := string(bout)
+	bout, err := cmd.Output()
+	stdout := string(bout)
+	stderr := ""
 	ecode := 0
 	if err != nil {
 		e, ok := err.(*exec.ExitError)
 		if !ok {
 			// e.g. could not respawn at all
-			t.Log(out)
+			t.Log(stdout)
 			t.Fatal(err)
 		}
+		stderr = string(e.Stderr)
 		ecode = e.ExitCode()
 	}
 
@@ -205,8 +207,8 @@ func verifyInSubprocess(t *testing.T, f func(t *testing.T), targvExtra ...string
 		badf("exit code: %d  ; expected: %d", ecode, expectOK.exitCode)
 	}
 
-	if out != expectOK.outputRe { // XXX match with re
-		badf("unexpected output:\n%s\nwant: %s\n", out, expectOK.outputRe)
+	if stderr != expectOK.stderrRe { // XXX match with re
+		badf("unexpected stderr:\n%s\nwant: %s\n", stderr, expectOK.stderrRe)
 	}
 
 	if bad != "" {
@@ -217,7 +219,7 @@ func verifyInSubprocess(t *testing.T, f func(t *testing.T), targvExtra ...string
 // testExpect describes what result to expect from a test.
 type testExpect struct {
 	exitCode int
-	outputRe string
+	stderrRe string
 }
 // testExpectMap maps <test name> -> testExpect.
 var testExpectMap = map[string]testExpect{