{ depot, lib, verifyTag, discr, discrDef, match, matchLam }:

let
  inherit (depot.nix.runTestsuite)
    runTestsuite
    assertEq
    it
    ;

  isTag-test = it "checks whether something is a tag" [
    (assertEq "is Tag"
      (verifyTag { foo = "bar"; })
      {
        isTag = true;
        name = "foo";
        val = "bar";
        errmsg = null;
      })
    (assertEq "is not Tag"
      (removeAttrs (verifyTag { foo = "bar"; baz = 42; }) ["errmsg"])
      {
        isTag = false;
        name = null;
        val = null;
      })
  ];

  discr-test = it "can discr things" [
    (assertEq "id"
      (discr [
        { a = lib.const true; }
      ] "x")
      { a = "x"; })
    (assertEq "bools here, ints there"
      (discr [
        { bool = lib.isBool; }
        { int = lib.isInt; }
      ] 25)
      { int = 25; })
    (assertEq "bools here, ints there 2"
      (discr [
        { bool = lib.isBool; }
        { int = lib.isInt; }
      ] true)
      { bool = true; })
    (assertEq "fallback to default"
      (discrDef "def" [
        { bool = lib.isBool; }
        { int = lib.isInt; }
      ] "foo")
      { def = "foo"; })
  ];

  match-test = it "can match things" [
    (assertEq "match example"
      (let
        success = { res = 42; };
        failure = { err = "no answer"; };
        matcher = {
          res = i: i + 1;
          err = _: 0;
        };
      in {
        one = match success matcher;
        two = match failure matcher;
      })
      { one = 43;
        two = 0; })
    (assertEq "matchLam & pipe"
      (lib.pipe { foo = 42; } [
        (matchLam {
          foo = i: if i < 23 then { small = i; } else { big = i; };
          bar = _: { small = 5; };
        })
        (matchLam {
          small = i: "yay it was small";
          big = i: "whoo it was big!";
        })
      ])
      "whoo it was big!")
  ];

in
  runTestsuite "tag" [
    isTag-test
    discr-test
    match-test
  ]