// Plan 9 needs to preserve environment variables with NUL (#56544).
			nulOK: true,
			in:    []string{"path=one\x00two"},
			want:  []string{"path=one\x00two"},
		},
	}
	for _, tt := range tests {
		got, err := dedupEnvCase(tt.noCase, tt.nulOK, tt.in)
		if !reflect.DeepEqual(got, tt.want) || (err != nil) != tt.wantErr {
			t.Errorf("Dedup(%v, %q) = %q, %v; want %q, error:%v", tt.noCase, tt.in, got, err, tt.want, tt.wantErr)
		}
	}

func dedupEnv(env []string) ([]string, error) {
	return dedupEnvCase(runtime.GOOS == "windows", runtime.GOOS == "plan9", env)
}

// dedupEnvCase is dedupEnv with a case option for testing.
// If caseInsensitive is true, the case of keys is ignored.
// If nulOK is false, items containing NUL characters are allowed.
func dedupEnvCase(caseInsensitive, nulOK bool, env []string) ([]string, error) {