defer func() { v4File.name = ipv4RouteFile }()

	// Should not occur, as caller ensures we have IPv4 route file, but being thorough
	v4File.name = "no-such-file"
	errStrFrag := "no such file"
	_, err := getAllDefaultRoutes()
	if err == nil {
		t.Errorf("Expected error trying to read non-existent v4 route file")
	}
	if !strings.Contains(err.Error(), errStrFrag) {