let
  inherit (import ../default.nix { }) pkgs;
  inherit (pkgs) lib;
  inherit (builtins) tryEval;
  inherit (lib) mkOption types;
  inherit (types)
    int
    str
    submodule
    ;
  functionType = submodule ./function.nix;
in
{
  _class = "nix-unit";

  test-function-ok = {
    expr =
      tryEval
        (lib.evalModules {
          modules = [
            (
              { config, ... }:
              {
                options = {
                  fn = mkOption {
                    type = functionType;
                  };
                  call = mkOption {
                    default = config.fn.apply 1;
                  };
                };
                config.fn = {
                  implementation = x: x;
                  input-type = int;
                  output-type = int;
                };
              }
            )
          ];
        }).config.call;
    expected = {
      success = true;
      value = 1;
    };
  };

  test-bad-input = {
    expr =
      tryEval
        (lib.evalModules {
          modules = [
            (
              { config, ... }:
              {
                options = {
                  fn = mkOption {
                    type = functionType;
                  };
                  call = mkOption {
                    default = config.fn.apply 1;
                  };
                };
                config.fn = {
                  implementation = x: x;
                  input-type = str;
                  output-type = int;
                };
              }
            )
          ];
        }).config.call;
    expected = {
      success = false;
      value = false;
    };
  };

  test-bad-output = {
    expr =
      tryEval
        (lib.evalModules {
          modules = [
            (
              { config, ... }:
              {
                options = {
                  fn = mkOption {
                    type = functionType;
                  };
                  call = mkOption {
                    default = config.fn.apply 1;
                  };
                };
                config.fn = {
                  implementation = x: x;
                  input-type = int;
                  output-type = str;
                };
              }
            )
          ];
        }).config.call;
    expected = {
      success = false;
      value = false;
    };
  };

  test-read-only = {
    expr =
      tryEval
        (lib.evalModules {
          modules = [
            (
              { config, ... }:
              {
                options = {
                  fn = mkOption {
                    type = functionType;
                  };
                  call = mkOption {
                    default = config.fn.apply { };
                  };
                };
                config.fn =
                  let
                    sub = submodule {
                      options.foo = mkOption {
                        type = int;
                        readOnly = true;
                        default = 1;
                      };
                    };
                  in
                  {
                    implementation = x: x;
                    input-type = sub;
                    output-type = sub;
                    type-output = false;
                  };
              }
            )
          ];
        }).config.call;
    expected = {
      success = true;
      value = {
        foo = 1;
      };
    };
  };
}