t.Fatal(syscall.Errno(errno))
	}
	defer func() {
		runtime.Close(r)
		runtime.Close(w)
	}()

	checkIsPipe(t, r, w)

	runtime.SetNonblock(r)
	runtime.SetNonblock(w)
	checkNonblocking(t, r, "reader")
	checkNonblocking(t, w, "writer")

	runtime.Closeonexec(r)
	runtime.Closeonexec(w)
	checkCloseonexec(t, r, "reader")
	checkCloseonexec(t, w, "writer")

	r, w, errno := runtime.NonblockingPipe()
	if errno != 0 {
		t.Fatal(syscall.Errno(errno))
	}
	defer runtime.Close(w)

	checkIsPipe(t, r, w)
	checkNonblocking(t, r, "reader")
	checkCloseonexec(t, r, "reader")
	checkNonblocking(t, w, "writer")
	checkCloseonexec(t, w, "writer")

	// Test that fcntl returns an error as expected.
	if runtime.Close(r) != 0 {
		t.Fatalf("Close(%d) failed", r)
	}