{
  programs.pistol = {
    enable = true;
    # contains both fpath and mime
    associations = [
      {
        fpath = ".*.md$";
        mime = "application/json";
        command = "bat %pistol-filename%";
      }
    ];
  };

  test.asserts.assertions.expected = [
    ''
      Each entry in programs.pistol.associations must contain exactly one
      of fpath or mime.
    ''
  ];
}