t.Logf("stderr: %s", string(errBuf.Bytes()))
			}
			t.Fatal(err)
		}
		tb := traceBuf.Bytes()

		// Test the trace and the parser.
		testReader(t, bytes.NewReader(tb), testtrace.ExpectSuccess())

		// Run some extra validation.
		if !t.Failed() && extra != nil {
			extra(t, tb, errBuf.Bytes(), stress)
		}

		// Dump some more information on failure.
		if t.Failed() && onBuilder {