/*
Nix evaluation tests for various lib functions.

Since these tests are implemented with Nix evaluation, error checking is limited to what `builtins.tryEval` can detect, which is `throw`'s and `abort`'s, without error messages.
If you need to test error messages or more complex evaluations, see ./modules.sh, ./sources.sh or ./filesystem.sh as examples.

To run these tests:

  [nixpkgs]$ nix-instantiate --eval --strict lib/tests/misc.nix

If the resulting list is empty, all tests passed.
Alternatively, to run all `lib` tests:

  [nixpkgs]$ nix-build lib/tests/release.nix
*/
with import ../default.nix;

let
  testingThrow = expr: {
    expr = (builtins.tryEval (builtins.seq expr "didn't throw"));
    expected = { success = false; value = false; };
  };
  testingDeepThrow = expr: testingThrow (builtins.deepSeq expr expr);

  testSanitizeDerivationName = { name, expected }:
  let
    drv = derivation {
      name = strings.sanitizeDerivationName name;
      builder = "x";
      system = "x";
    };
  in {
    # Evaluate the derivation so an invalid name would be caught
    expr = builtins.seq drv.drvPath drv.name;
    inherit expected;
  };

in

runTests {

# TRIVIAL

  testId = {
    expr = id 1;
    expected = 1;
  };

  testConst = {
    expr = const 2 3;
    expected = 2;
  };

  testPipe = {
    expr = pipe 2 [
      (x: x + 2) # 2 + 2 = 4
      (x: x * 2) # 4 * 2 = 8
    ];
    expected = 8;
  };

  testPipeEmpty = {
    expr = pipe 2 [];
    expected = 2;
  };

  testPipeStrings = {
    expr = pipe [ 3 4 ] [
      (map toString)
      (map (s: s + "\n"))
      concatStrings
    ];
    expected = ''
      3
      4
    '';
  };

  /*
  testOr = {
    expr = or true false;
    expected = true;
  };
  */

  testAnd = {
    expr = and true false;
    expected = false;
  };

  testFix = {
    expr = fix (x: {a = if x ? a then "a" else "b";});
    expected = {a = "a";};
  };

  testComposeExtensions = {
    expr = let obj = makeExtensible (self: { foo = self.bar; });
               f = self: super: { bar = false; baz = true; };
               g = self: super: { bar = super.baz or false; };
               f_o_g = composeExtensions f g;
               composed = obj.extend f_o_g;
           in composed.foo;
    expected = true;
  };

  testComposeManyExtensions0 = {
    expr = let obj = makeExtensible (self: { foo = true; });
               emptyComposition = composeManyExtensions [];
               composed = obj.extend emptyComposition;
           in composed.foo;
    expected = true;
  };

  testComposeManyExtensions =
    let f = self: super: { bar = false; baz = true; };
        g = self: super: { bar = super.baz or false; };
        h = self: super: { qux = super.bar or false; };
        obj = makeExtensible (self: { foo = self.qux; });
    in {
    expr = let composition = composeManyExtensions [f g h];
               composed = obj.extend composition;
           in composed.foo;
    expected = (obj.extend (composeExtensions f (composeExtensions g h))).foo;
  };

  testBitAnd = {
    expr = (bitAnd 3 10);
    expected = 2;
  };

  testBitOr = {
    expr = (bitOr 3 10);
    expected = 11;
  };

  testBitXor = {
    expr = (bitXor 3 10);
    expected = 9;
  };

  testToHexString = {
    expr = toHexString 250;
    expected = "FA";
  };

  testToBaseDigits = {
    expr = toBaseDigits 2 6;
    expected = [ 1 1 0 ];
  };

  testFunctionArgsFunctor = {
    expr = functionArgs { __functor = self: { a, b }: null; };
    expected = { a = false; b = false; };
  };

  testFunctionArgsSetFunctionArgs = {
    expr = functionArgs (setFunctionArgs (args: args.x) { x = false; });
    expected = { x = false; };
  };

# STRINGS

  testConcatMapStrings = {
    expr = concatMapStrings (x: x + ";") ["a" "b" "c"];
    expected = "a;b;c;";
  };

  testConcatStringsSep = {
    expr = concatStringsSep "," ["a" "b" "c"];
    expected = "a,b,c";
  };

  testConcatLines = {
    expr = concatLines ["a" "b" "c"];
    expected = "a\nb\nc\n";
  };

  testSplitStringsSimple = {
    expr = strings.splitString "." "a.b.c.d";
    expected = [ "a" "b" "c" "d" ];
  };

  testSplitStringsEmpty = {
    expr = strings.splitString "." "a..b";
    expected = [ "a" "" "b" ];
  };

  testSplitStringsOne = {
    expr = strings.splitString ":" "a.b";
    expected = [ "a.b" ];
  };

  testSplitStringsNone = {
    expr = strings.splitString "." "";
    expected = [ "" ];
  };

  testSplitStringsFirstEmpty = {
    expr = strings.splitString "/" "/a/b/c";
    expected = [ "" "a" "b" "c" ];
  };

  testSplitStringsLastEmpty = {
    expr = strings.splitString ":" "2001:db8:0:0042::8a2e:370:";
    expected = [ "2001" "db8" "0" "0042" "" "8a2e" "370" "" ];
  };

  testSplitStringsRegex = {
    expr = strings.splitString "\\[{}]()^$?*+|." "A\\[{}]()^$?*+|.B";
    expected = [ "A" "B" ];
  };

  testSplitStringsDerivation = {
    expr = take 3  (strings.splitString "/" (derivation {
      name = "name";
      builder = "builder";
      system = "system";
    }));
    expected = ["" "nix" "store"];
  };

  testSplitVersionSingle = {
    expr = versions.splitVersion "1";
    expected = [ "1" ];
  };

  testSplitVersionDouble = {
    expr = versions.splitVersion "1.2";
    expected = [ "1" "2" ];
  };

  testSplitVersionTriple = {
    expr = versions.splitVersion "1.2.3";
    expected = [ "1" "2" "3" ];
  };

  testPadVersionLess = {
    expr = versions.pad 3 "1.2";
    expected = "1.2.0";
  };

  testPadVersionLessExtra = {
    expr = versions.pad 3 "1.3-rc1";
    expected = "1.3.0-rc1";
  };

  testPadVersionMore = {
    expr = versions.pad 3 "1.2.3.4";
    expected = "1.2.3";
  };

  testIsStorePath =  {
    expr =
      let goodPath =
            "${builtins.storeDir}/d945ibfx9x185xf04b890y4f9g3cbb63-python-2.7.11";
      in {
        storePath = isStorePath goodPath;
        storePathDerivation = isStorePath (import ../.. { system = "x86_64-linux"; }).hello;
        storePathAppendix = isStorePath
          "${goodPath}/bin/python";
        nonAbsolute = isStorePath (concatStrings (tail (stringToCharacters goodPath)));
        asPath = isStorePath (/. + goodPath);
        otherPath = isStorePath "/something/else";
        otherVals = {
          attrset = isStorePath {};
          list = isStorePath [];
          int = isStorePath 42;
        };
      };
    expected = {
      storePath = true;
      storePathDerivation = true;
      storePathAppendix = false;
      nonAbsolute = false;
      asPath = true;
      otherPath = false;
      otherVals = {
        attrset = false;
        list = false;
        int = false;
      };
    };
  };

  testEscapeXML = {
    expr = escapeXML ''"test" 'test' < & >'';
    expected = "&quot;test&quot; &apos;test&apos; &lt; &amp; &gt;";
  };

  testToShellVars = {
    expr = ''
      ${toShellVars {
        STRing01 = "just a 'string'";
        _array_ = [ "with" "more strings" ];
        assoc."with some" = ''
          strings
          possibly newlines
        '';
        drv = {
          outPath = "/drv";
          foo = "ignored attribute";
        };
        path = /path;
        stringable = {
          __toString = _: "hello toString";
          bar = "ignored attribute";
        };
      }}
    '';
    expected = ''
      STRing01='just a '\'''string'\''''
      declare -a _array_=('with' 'more strings')
      declare -A assoc=(['with some']='strings
      possibly newlines
      ')
      drv='/drv'
      path='/path'
      stringable='hello toString'
    '';
  };

  testHasInfixFalse = {
    expr = hasInfix "c" "abde";
    expected = false;
  };

  testHasInfixTrue = {
    expr = hasInfix "c" "abcde";
    expected = true;
  };

  testHasInfixDerivation = {
    expr = hasInfix "hello" (import ../.. { system = "x86_64-linux"; }).hello;
    expected = true;
  };

  testHasInfixPath = {
    expr = hasInfix "tests" ./.;
    expected = true;
  };

  testHasInfixPathStoreDir = {
    expr = hasInfix builtins.storeDir ./.;
    expected = true;
  };

  testHasInfixToString = {
    expr = hasInfix "a" { __toString = _: "a"; };
    expected = true;
  };

  testRemovePrefixExample1 = {
    expr = removePrefix "foo." "foo.bar.baz";
    expected = "bar.baz";
  };
  testRemovePrefixExample2 = {
    expr = removePrefix "xxx" "foo.bar.baz";
    expected = "foo.bar.baz";
  };
  testRemovePrefixEmptyPrefix = {
    expr = removePrefix "" "foo";
    expected = "foo";
  };
  testRemovePrefixEmptyString = {
    expr = removePrefix "foo" "";
    expected = "";
  };
  testRemovePrefixEmptyBoth = {
    expr = removePrefix "" "";
    expected = "";
  };

  testNormalizePath = {
    expr = strings.normalizePath "//a/b//c////d/";
    expected = "/a/b/c/d/";
  };

  testCharToInt = {
    expr = strings.charToInt "A";
    expected = 65;
  };

  testEscapeC = {
    expr = strings.escapeC [ " " ] "Hello World";
    expected = "Hello\\x20World";
  };

  testEscapeURL = testAllTrue [
    ("" == strings.escapeURL "")
    ("Hello" == strings.escapeURL "Hello")
    ("Hello%20World" == strings.escapeURL "Hello World")
    ("Hello%2FWorld" == strings.escapeURL "Hello/World")
    ("42%25" == strings.escapeURL "42%")
    ("%20%3F%26%3D%23%2B%25%21%3C%3E%23%22%7B%7D%7C%5C%5E%5B%5D%60%09%3A%2F%40%24%27%28%29%2A%2C%3B" == strings.escapeURL " ?&=#+%!<>#\"{}|\\^[]`\t:/@$'()*,;")
  ];

  testToInt = testAllTrue [
    # Naive
    (123 == toInt "123")
    (0 == toInt "0")
    # Whitespace Padding
    (123 == toInt " 123")
    (123 == toInt "123 ")
    (123 == toInt " 123 ")
    (123 == toInt "   123   ")
    (0 == toInt " 0")
    (0 == toInt "0 ")
    (0 == toInt " 0 ")
    (-1 == toInt "-1")
    (-1 == toInt " -1 ")
  ];

  testToIntFails = testAllTrue [
    ( builtins.tryEval (toInt "") == { success = false; value = false; } )
    ( builtins.tryEval (toInt "123 123") == { success = false; value = false; } )
    ( builtins.tryEval (toInt "0 123") == { success = false; value = false; } )
    ( builtins.tryEval (toInt " 0d ") == { success = false; value = false; } )
    ( builtins.tryEval (toInt " 1d ") == { success = false; value = false; } )
    ( builtins.tryEval (toInt " d0 ") == { success = false; value = false; } )
    ( builtins.tryEval (toInt "00") == { success = false; value = false; } )
    ( builtins.tryEval (toInt "01") == { success = false; value = false; } )
    ( builtins.tryEval (toInt "002") == { success = false; value = false; } )
    ( builtins.tryEval (toInt " 002 ") == { success = false; value = false; } )
    ( builtins.tryEval (toInt " foo ") == { success = false; value = false; } )
    ( builtins.tryEval (toInt " foo 123 ") == { success = false; value = false; } )
    ( builtins.tryEval (toInt " foo123 ") == { success = false; value = false; } )
  ];

  testToIntBase10 = testAllTrue [
    # Naive
    (123 == toIntBase10 "123")
    (0 == toIntBase10 "0")
    # Whitespace Padding
    (123 == toIntBase10 " 123")
    (123 == toIntBase10 "123 ")
    (123 == toIntBase10 " 123 ")
    (123 == toIntBase10 "   123   ")
    (0 == toIntBase10 " 0")
    (0 == toIntBase10 "0 ")
    (0 == toIntBase10 " 0 ")
    # Zero Padding
    (123 == toIntBase10 "0123")
    (123 == toIntBase10 "0000123")
    (0 == toIntBase10 "000000")
    # Whitespace and Zero Padding
    (123 == toIntBase10 " 0123")
    (123 == toIntBase10 "0123 ")
    (123 == toIntBase10 " 0123 ")
    (123 == toIntBase10 " 0000123")
    (123 == toIntBase10 "0000123 ")
    (123 == toIntBase10 " 0000123 ")
    (0 == toIntBase10 " 000000")
    (0 == toIntBase10 "000000 ")
    (0 == toIntBase10 " 000000 ")
    (-1 == toIntBase10 "-1")
    (-1 == toIntBase10 " -1 ")
  ];

  testToIntBase10Fails = testAllTrue [
    ( builtins.tryEval (toIntBase10 "") == { success = false; value = false; } )
    ( builtins.tryEval (toIntBase10 "123 123") == { success = false; value = false; } )
    ( builtins.tryEval (toIntBase10 "0 123") == { success = false; value = false; } )
    ( builtins.tryEval (toIntBase10 " 0d ") == { success = false; value = false; } )
    ( builtins.tryEval (toIntBase10 " 1d ") == { success = false; value = false; } )
    ( builtins.tryEval (toIntBase10 " d0 ") == { success = false; value = false; } )
    ( builtins.tryEval (toIntBase10 " foo ") == { success = false; value = false; } )
    ( builtins.tryEval (toIntBase10 " foo 123 ") == { success = false; value = false; } )
    ( builtins.tryEval (toIntBase10 " foo 00123 ") == { success = false; value = false; } )
    ( builtins.tryEval (toIntBase10 " foo00123 ") == { success = false; value = false; } )
  ];

# LISTS

  testFilter = {
    expr = filter (x: x != "a") ["a" "b" "c" "a"];
    expected = ["b" "c"];
  };

  testFold =
    let
      f = op: fold: fold op 0 (range 0 100);
      # fold with associative operator
      assoc = f builtins.add;
      # fold with non-associative operator
      nonAssoc = f builtins.sub;
    in {
      expr = {
        assocRight = assoc foldr;
        # right fold with assoc operator is same as left fold
        assocRightIsLeft = assoc foldr == assoc foldl;
        nonAssocRight = nonAssoc foldr;
        nonAssocLeft = nonAssoc foldl;
        # with non-assoc operator the fold results are not the same
        nonAssocRightIsNotLeft = nonAssoc foldl != nonAssoc foldr;
        # fold is an alias for foldr
        foldIsRight = nonAssoc fold == nonAssoc foldr;
      };
      expected = {
        assocRight = 5050;
        assocRightIsLeft = true;
        nonAssocRight = 50;
        nonAssocLeft = (-5050);
        nonAssocRightIsNotLeft = true;
        foldIsRight = true;
      };
    };

  testFoldl'Empty = {
    expr = foldl' (acc: el: abort "operation not called") 0 [ ];
    expected = 0;
  };

  testFoldl'IntegerAdding = {
    expr = foldl' (acc: el: acc + el) 0 [ 1 2 3 ];
    expected = 6;
  };

  # The accumulator isn't forced deeply
  testFoldl'NonDeep = {
    expr = take 3 (foldl'
      (acc: el: [ el ] ++ acc)
      [ (abort "unevaluated list entry") ]
      [ 1 2 3 ]);
    expected = [ 3 2 1 ];
  };

  # Compared to builtins.foldl', lib.foldl' evaluates the first accumulator strictly too
  testFoldl'StrictInitial = {
    expr = (builtins.tryEval (foldl' (acc: el: el) (throw "hello") [])).success;
    expected = false;
  };

  # Make sure we don't get a stack overflow for large lists
  # This number of elements would notably cause a stack overflow if it was implemented without the `foldl'` builtin
  testFoldl'Large = {
    expr = foldl' (acc: el: acc + el) 0 (range 0 100000);
    expected = 5000050000;
  };

  testTake = testAllTrue [
    ([] == (take 0 [  1 2 3 ]))
    ([1] == (take 1 [  1 2 3 ]))
    ([ 1 2 ] == (take 2 [  1 2 3 ]))
    ([ 1 2 3 ] == (take 3 [  1 2 3 ]))
    ([ 1 2 3 ] == (take 4 [  1 2 3 ]))
  ];

  testListHasPrefixExample1 = {
    expr = lists.hasPrefix [ 1 2 ] [ 1 2 3 4 ];
    expected = true;
  };
  testListHasPrefixExample2 = {
    expr = lists.hasPrefix [ 0 1 ] [ 1 2 3 4 ];
    expected = false;
  };
  testListHasPrefixLazy = {
    expr = lists.hasPrefix [ 1 ] [ 1 (abort "lib.lists.hasPrefix is not lazy") ];
    expected = true;
  };
  testListHasPrefixEmptyPrefix = {
    expr = lists.hasPrefix [ ] [ 1 2 ];
    expected = true;
  };
  testListHasPrefixEmptyList = {
    expr = lists.hasPrefix [ 1 2 ] [ ];
    expected = false;
  };

  testListRemovePrefixExample1 = {
    expr = lists.removePrefix [ 1 2 ] [ 1 2 3 4 ];
    expected = [ 3 4 ];
  };
  testListRemovePrefixExample2 = {
    expr = (builtins.tryEval (lists.removePrefix [ 0 1 ] [ 1 2 3 4 ])).success;
    expected = false;
  };
  testListRemovePrefixEmptyPrefix = {
    expr = lists.removePrefix [ ] [ 1 2 ];
    expected = [ 1 2 ];
  };
  testListRemovePrefixEmptyList = {
    expr = (builtins.tryEval (lists.removePrefix [ 1 2 ] [ ])).success;
    expected = false;
  };

  testFoldAttrs = {
    expr = foldAttrs (n: a: [n] ++ a) [] [
    { a = 2; b = 7; }
    { a = 3;        c = 8; }
    ];
    expected = { a = [ 2 3 ]; b = [7]; c = [8];};
  };

  testListCommonPrefixExample1 = {
    expr = lists.commonPrefix [ 1 2 3 4 5 6 ] [ 1 2 4 8 ];
    expected = [ 1 2 ];
  };
  testListCommonPrefixExample2 = {
    expr = lists.commonPrefix [ 1 2 3 ] [ 1 2 3 4 5 ];
    expected = [ 1 2 3 ];
  };
  testListCommonPrefixExample3 = {
    expr = lists.commonPrefix [ 1 2 3 ] [ 4 5 6 ];
    expected = [ ];
  };
  testListCommonPrefixEmpty = {
    expr = lists.commonPrefix [ ] [ 1 2 3 ];
    expected = [ ];
  };
  testListCommonPrefixSame = {
    expr = lists.commonPrefix [ 1 2 3 ] [ 1 2 3 ];
    expected = [ 1 2 3 ];
  };
  testListCommonPrefixLazy = {
    expr = lists.commonPrefix [ 1 ] [ 1 (abort "lib.lists.commonPrefix shouldn't evaluate this")];
    expected = [ 1 ];
  };
  # This would stack overflow if `commonPrefix` were implemented using recursion
  testListCommonPrefixLong =
    let
      longList = genList (n: n) 100000;
    in {
      expr = lists.commonPrefix longList longList;
      expected = longList;
    };

  testSort = {
    expr = sort builtins.lessThan [ 40 2 30 42 ];
    expected = [2 30 40 42];
  };

  testReplicate = {
    expr = replicate 3 "a";
    expected = ["a" "a" "a"];
  };

  testToIntShouldConvertStringToInt = {
    expr = toInt "27";
    expected = 27;
  };

  testToIntShouldThrowErrorIfItCouldNotConvertToInt = {
    expr = builtins.tryEval (toInt "\"foo\"");
    expected = { success = false; value = false; };
  };

  testHasAttrByPathTrue = {
    expr = hasAttrByPath ["a" "b"] { a = { b = "yey"; }; };
    expected = true;
  };

  testHasAttrByPathFalse = {
    expr = hasAttrByPath ["a" "b"] { a = { c = "yey"; }; };
    expected = false;
  };

  testFindFirstIndexExample1 = {
    expr = lists.findFirstIndex (x: x > 3) (abort "index found, so a default must not be evaluated") [ 1 6 4 ];
    expected = 1;
  };

  testFindFirstIndexExample2 = {
    expr = lists.findFirstIndex (x: x > 9) "a very specific default" [ 1 6 4 ];
    expected = "a very specific default";
  };

  testFindFirstIndexEmpty = {
    expr = lists.findFirstIndex (abort "when the list is empty, the predicate is not needed") null [];
    expected = null;
  };

  testFindFirstIndexSingleMatch = {
    expr = lists.findFirstIndex (x: x == 5) null [ 5 ];
    expected = 0;
  };

  testFindFirstIndexSingleDefault = {
    expr = lists.findFirstIndex (x: false) null [ (abort "if the predicate doesn't access the value, it must not be evaluated") ];
    expected = null;
  };

  testFindFirstIndexNone = {
    expr = builtins.tryEval (lists.findFirstIndex (x: x == 2) null [ 1 (throw "the last element must be evaluated when there's no match") ]);
    expected = { success = false; value = false; };
  };

  # Makes sure that the implementation doesn't cause a stack overflow
  testFindFirstIndexBig = {
    expr = lists.findFirstIndex (x: x == 1000000) null (range 0 1000000);
    expected = 1000000;
  };

  testFindFirstIndexLazy = {
    expr = lists.findFirstIndex (x: x == 1) null [ 1 (abort "list elements after the match must not be evaluated") ];
    expected = 0;
  };

  testFindFirstExample1 = {
    expr = lists.findFirst (x: x > 3) 7 [ 1 6 4 ];
    expected = 6;
  };

  testFindFirstExample2 = {
    expr = lists.findFirst (x: x > 9) 7 [ 1 6 4 ];
    expected = 7;
  };

# ATTRSETS

  testConcatMapAttrs = {
    expr = concatMapAttrs
      (name: value: {
        ${name} = value;
        ${name + value} = value;
      })
      {
        foo = "bar";
        foobar = "baz";
      };
    expected = {
      foo = "bar";
      foobar = "baz";
      foobarbaz = "baz";
    };
  };

  # code from example
  testFoldlAttrs = {
    expr = {
      example = foldlAttrs
        (acc: name: value: {
          sum = acc.sum + value;
          names = acc.names ++ [ name ];
        })
        { sum = 0; names = [ ]; }
        {
          foo = 1;
          bar = 10;
        };
      # should just return the initial value
      emptySet = foldlAttrs (throw "function not needed") 123 { };
      # should just evaluate to the last value
      valuesNotNeeded = foldlAttrs (acc: _name: _v: acc) 3 { z = throw "value z not needed"; a = throw "value a not needed"; };
      # the accumulator doesnt have to be an attrset it can be as trivial as being just a number or string
      trivialAcc = foldlAttrs (acc: _name: v: acc * 10 + v) 1 { z = 1; a = 2; };
    };
    expected = {
      example = {
        sum = 11;
        names = [ "bar" "foo" ];
      };
      emptySet = 123;
      valuesNotNeeded = 3;
      trivialAcc = 121;
    };
  };


  testMergeAttrsListExample1 = {
    expr = attrsets.mergeAttrsList [ { a = 0; b = 1; } { c = 2; d = 3; } ];
    expected = { a = 0; b = 1; c = 2; d = 3; };
  };
  testMergeAttrsListExample2 = {
    expr = attrsets.mergeAttrsList [ { a = 0; } { a = 1; } ];
    expected = { a = 1; };
  };
  testMergeAttrsListExampleMany =
    let
      list = genList (n:
        listToAttrs (genList (m:
          let
            # Integer divide n by two to create duplicate attributes
            str = "halfn${toString (n / 2)}m${toString m}";
          in
          nameValuePair str str
        ) 100)
      ) 100;
    in {
      expr = attrsets.mergeAttrsList list;
      expected = foldl' mergeAttrs { } list;
    };

  # code from the example
  testRecursiveUpdateUntil = {
    expr = recursiveUpdateUntil (path: l: r: path == ["foo"]) {
      # first attribute set
      foo.bar = 1;
      foo.baz = 2;
      bar = 3;
    } {
      #second attribute set
      foo.bar = 1;
      foo.quz = 2;
      baz = 4;
    };
    expected = {
      foo.bar = 1; # 'foo.*' from the second set
      foo.quz = 2; #
      bar = 3;     # 'bar' from the first set
      baz = 4;     # 'baz' from the second set
    };
  };

  testOverrideExistingEmpty = {
    expr = overrideExisting {} { a = 1; };
    expected = {};
  };

  testOverrideExistingDisjoint = {
    expr = overrideExisting { b = 2; } { a = 1; };
    expected = { b = 2; };
  };

  testOverrideExistingOverride = {
    expr = overrideExisting { a = 3; b = 2; } { a = 1; };
    expected = { a = 1; b = 2; };
  };

# GENERATORS
# these tests assume attributes are converted to lists
# in alphabetical order

  testMkKeyValueDefault = {
    expr = generators.mkKeyValueDefault {} ":" "f:oo" "bar";
    expected = ''f\:oo:bar'';
  };

  testMkValueString = {
    expr = let
      vals = {
        int = 42;
        string = ''fo"o'';
        bool = true;
        bool2 = false;
        null = null;
        # float = 42.23; # floats are strange
      };
      in mapAttrs
        (const (generators.mkValueStringDefault {}))
        vals;
    expected = {
      int = "42";
      string = ''fo"o'';
      bool = "true";
      bool2 = "false";
      null = "null";
      # float = "42.23" true false [ "bar" ] ]'';
    };
  };

  testToKeyValue = {
    expr = generators.toKeyValue {} {
      key = "value";
      "other=key" = "baz";
    };
    expected = ''
      key=value
      other\=key=baz
    '';
  };

  testToINIEmpty = {
    expr = generators.toINI {} {};
    expected = "";
  };

  testToINIEmptySection = {
    expr = generators.toINI {} { foo = {}; bar = {}; };
    expected = ''
      [bar]

      [foo]
    '';
  };

  testToINIDuplicateKeys = {
    expr = generators.toINI { listsAsDuplicateKeys = true; } { foo.bar = true; baz.qux = [ 1 false ]; };
    expected = ''
      [baz]
      qux=1
      qux=false

      [foo]
      bar=true
    '';
  };

  testToINIDefaultEscapes = {
    expr = generators.toINI {} {
      "no [ and ] allowed unescaped" = {
        "and also no = in keys" = 42;
      };
    };
    expected = ''
      [no \[ and \] allowed unescaped]
      and also no \= in keys=42
    '';
  };

  testToINIDefaultFull = {
    expr = generators.toINI {} {
      "section 1" = {
        attribute1 = 5;
        x = "Me-se JarJar Binx";
        # booleans are converted verbatim by default
        boolean = false;
      };
      "foo[]" = {
        "he\\h=he" = "this is okay";
      };
    };
    expected = ''
      [foo\[\]]
      he\h\=he=this is okay

      [section 1]
      attribute1=5
      boolean=false
      x=Me-se JarJar Binx
    '';
  };

  testToINIWithGlobalSectionEmpty = {
    expr = generators.toINIWithGlobalSection {} {
      globalSection = {
      };
      sections = {
      };
    };
    expected = ''
    '';
  };

  testToINIWithGlobalSectionGlobalEmptyIsTheSameAsToINI =
    let
      sections = {
        "section 1" = {
          attribute1 = 5;
          x = "Me-se JarJar Binx";
        };
        "foo" = {
          "he\\h=he" = "this is okay";
        };
      };
    in {
      expr =
        generators.toINIWithGlobalSection {} {
            globalSection = {};
            sections = sections;
        };
      expected = generators.toINI {} sections;
  };

  testToINIWithGlobalSectionFull = {
    expr = generators.toINIWithGlobalSection {} {
      globalSection = {
        foo = "bar";
        test = false;
      };
      sections = {
        "section 1" = {
          attribute1 = 5;
          x = "Me-se JarJar Binx";
        };
        "foo" = {
          "he\\h=he" = "this is okay";
        };
      };
    };
    expected = ''
      foo=bar
      test=false

      [foo]
      he\h\=he=this is okay

      [section 1]
      attribute1=5
      x=Me-se JarJar Binx
    '';
  };

  testToGitINI = {
    expr = generators.toGitINI {
      user = {
        email = "user@example.org";
        name = "John Doe";
        signingKey = "00112233445566778899AABBCCDDEEFF";
      };
      gpg.program = "path-to-gpg";
      tag.gpgSign = true;
      include.path = "~/path/to/config.inc";
      includeIf."gitdif:~/src/dir".path = "~/path/to/conditional.inc";
      extra = {
        boolean = true;
        integer = 38;
        name = "value";
        subsection.value = "test";
      };};
    expected = ''
      [extra]
      ${"\t"}boolean = true
      ${"\t"}integer = 38
      ${"\t"}name = "value"

      [extra "subsection"]
      ${"\t"}value = "test"

      [gpg]
      ${"\t"}program = "path-to-gpg"

      [include]
      ${"\t"}path = "~/path/to/config.inc"

      [includeIf "gitdif:~/src/dir"]
      ${"\t"}path = "~/path/to/conditional.inc"

      [tag]
      ${"\t"}gpgSign = true

      [user]
      ${"\t"}email = "user@example.org"
      ${"\t"}name = "John Doe"
      ${"\t"}signingKey = "00112233445566778899AABBCCDDEEFF"
    '';
  };

  /* right now only invocation check */
  testToJSONSimple =
    let val = {
      foobar = [ "baz" 1 2 3 ];
    };
    in {
      expr = generators.toJSON {} val;
      # trivial implementation
      expected = builtins.toJSON val;
  };

  /* right now only invocation check */
  testToYAMLSimple =
    let val = {
      list = [ { one = 1; } { two = 2; } ];
      all = 42;
    };
    in {
      expr = generators.toYAML {} val;
      # trivial implementation
      expected = builtins.toJSON val;
  };

  testToPretty =
    let
      deriv = derivation { name = "test"; builder = "/bin/sh"; system = "aarch64-linux"; };
    in {
    expr = mapAttrs (const (generators.toPretty { multiline = false; })) rec {
      int = 42;
      float = 0.1337;
      bool = true;
      emptystring = "";
      string = "fn\${o}\"r\\d";
      newlinestring = "\n";
      path = /. + "/foo";
      null_ = null;
      function = x: x;
      functionArgs = { arg ? 4, foo }: arg;
      list = [ 3 4 function [ false ] ];
      emptylist = [];
      attrs = { foo = null; "foo b/ar" = "baz"; };
      emptyattrs = {};
      drv = deriv;
    };
    expected = rec {
      int = "42";
      float = "0.1337";
      bool = "true";
      emptystring = ''""'';
      string = ''"fn\''${o}\"r\\d"'';
      newlinestring = "\"\\n\"";
      path = "/foo";
      null_ = "null";
      function = "<function>";
      functionArgs = "<function, args: {arg?, foo}>";
      list = "[ 3 4 ${function} [ false ] ]";
      emptylist = "[ ]";
      attrs = "{ foo = null; \"foo b/ar\" = \"baz\"; }";
      emptyattrs = "{ }";
      drv = "<derivation ${deriv.name}>";
    };
  };

  testToPrettyLimit =
    let
      a.b = 1;
      a.c = a;
    in {
      expr = generators.toPretty { } (generators.withRecursion { throwOnDepthLimit = false; depthLimit = 2; } a);
      expected = "{\n  b = 1;\n  c = {\n    b = \"<unevaluated>\";\n    c = {\n      b = \"<unevaluated>\";\n      c = \"<unevaluated>\";\n    };\n  };\n}";
    };

  testToPrettyLimitThrow =
    let
      a.b = 1;
      a.c = a;
    in {
      expr = (builtins.tryEval
        (generators.toPretty { } (generators.withRecursion { depthLimit = 2; } a))).success;
      expected = false;
    };

  testWithRecursionDealsWithFunctors =
    let
      functor = {
        __functor = self: { a, b, }: null;
      };
      a = {
        value = "1234";
        b = functor;
        c.d = functor;
      };
    in {
      expr = generators.toPretty { } (generators.withRecursion { depthLimit = 1; throwOnDepthLimit = false; } a);
      expected = "{\n  b = <function, args: {a, b}>;\n  c = {\n    d = \"<unevaluated>\";\n  };\n  value = \"<unevaluated>\";\n}";
    };

  testToPrettyMultiline = {
    expr = mapAttrs (const (generators.toPretty { })) rec {
      list = [ 3 4 [ false ] ];
      attrs = { foo = null; bar.foo = "baz"; };
      newlinestring = "\n";
      multilinestring = ''
        hello
        ''${there}
        te'''st
      '';
      multilinestring' = ''
        hello
        there
        test'';
    };
    expected = rec {
      list = ''
        [
          3
          4
          [
            false
          ]
        ]'';
      attrs = ''
        {
          bar = {
            foo = "baz";
          };
          foo = null;
        }'';
      newlinestring = "''\n  \n''";
      multilinestring = ''
        '''
          hello
          '''''${there}
          te''''st
        ''''';
      multilinestring' = ''
        '''
          hello
          there
          test''''';

    };
  };

  testToPrettyAllowPrettyValues = {
    expr = generators.toPretty { allowPrettyValues = true; }
             { __pretty = v: "«" + v + "»"; val = "foo"; };
    expected  = "«foo»";
  };

  testToPlist =
    let
      deriv = derivation { name = "test"; builder = "/bin/sh"; system = "aarch64-linux"; };
    in {
    expr = mapAttrs (const (generators.toPlist { })) {
      value = {
        nested.values = rec {
          int = 42;
          float = 0.1337;
          bool = true;
          emptystring = "";
          string = "fn\${o}\"r\\d";
          newlinestring = "\n";
          path = /. + "/foo";
          null_ = null;
          list = [ 3 4 "test" ];
          emptylist = [];
          attrs = { foo = null; "foo b/ar" = "baz"; };
          emptyattrs = {};
        };
      };
    };
    expected = { value = builtins.readFile ./test-to-plist-expected.plist; };
  };

  testToLuaEmptyAttrSet = {
    expr = generators.toLua {} {};
    expected = ''{}'';
  };

  testToLuaEmptyList = {
    expr = generators.toLua {} [];
    expected = ''{}'';
  };

  testToLuaListOfVariousTypes = {
    expr = generators.toLua {} [ null 43 3.14159 true ];
    expected = ''
      {
        nil,
        43,
        3.14159,
        true
      }'';
  };

  testToLuaString = {
    expr = generators.toLua {} ''double-quote (") and single quotes (')'';
    expected = ''"double-quote (\") and single quotes (')"'';
  };

  testToLuaAttrsetWithLuaInline = {
    expr = generators.toLua {} { x = generators.mkLuaInline ''"abc" .. "def"''; };
    expected = ''
      {
        ["x"] = ("abc" .. "def")
      }'';
  };

  testToLuaAttrsetWithSpaceInKey = {
    expr = generators.toLua {} { "some space and double-quote (\")" = 42; };
    expected = ''
      {
        ["some space and double-quote (\")"] = 42
      }'';
  };

  testToLuaWithoutMultiline = {
    expr = generators.toLua { multiline = false; } [ 41 43 ];
    expected = ''{ 41, 43 }'';
  };

  testToLuaEmptyBindings = {
    expr = generators.toLua { asBindings = true; } {};
    expected = "";
  };

  testToLuaBindings = {
    expr = generators.toLua { asBindings = true; } { x1 = 41; _y = { a = 43; }; };
    expected = ''
      _y = {
        ["a"] = 43
      }
      x1 = 41
    '';
  };

  testToLuaPartialTableBindings = {
    expr = generators.toLua { asBindings = true; } { "x.y" = 42; };
    expected = ''
      x.y = 42
    '';
  };

  testToLuaIndentedBindings = {
    expr = generators.toLua { asBindings = true; indent = "  "; } { x = { y = 42; }; };
    expected = "  x = {\n    [\"y\"] = 42\n  }\n";
  };

  testToLuaBindingsWithSpace = testingThrow (
    generators.toLua { asBindings = true; } { "with space" = 42; }
  );

  testToLuaBindingsWithLeadingDigit = testingThrow (
    generators.toLua { asBindings = true; } { "11eleven" = 42; }
  );

  testToLuaBasicExample = {
    expr = generators.toLua {} {
      cmd = [ "typescript-language-server" "--stdio" ];
      settings.workspace.library = generators.mkLuaInline ''vim.api.nvim_get_runtime_file("", true)'';
    };
    expected = ''
      {
        ["cmd"] = {
          "typescript-language-server",
          "--stdio"
        },
        ["settings"] = {
          ["workspace"] = {
            ["library"] = (vim.api.nvim_get_runtime_file("", true))
          }
        }
      }'';
  };

# CLI

  testToGNUCommandLine = {
    expr = cli.toGNUCommandLine {} {
      data = builtins.toJSON { id = 0; };
      X = "PUT";
      retry = 3;
      retry-delay = null;
      url = [ "https://example.com/foo" "https://example.com/bar" ];
      silent = false;
      verbose = true;
    };

    expected = [
      "-X" "PUT"
      "--data" "{\"id\":0}"
      "--retry" "3"
      "--url" "https://example.com/foo"
      "--url" "https://example.com/bar"
      "--verbose"
    ];
  };

  testToGNUCommandLineShell = {
    expr = cli.toGNUCommandLineShell {} {
      data = builtins.toJSON { id = 0; };
      X = "PUT";
      retry = 3;
      retry-delay = null;
      url = [ "https://example.com/foo" "https://example.com/bar" ];
      silent = false;
      verbose = true;
    };

    expected = "'-X' 'PUT' '--data' '{\"id\":0}' '--retry' '3' '--url' 'https://example.com/foo' '--url' 'https://example.com/bar' '--verbose'";
  };

  testSanitizeDerivationNameLeadingDots = testSanitizeDerivationName {
    name = "..foo";
    expected = "foo";
  };

  testSanitizeDerivationNameUnicode = testSanitizeDerivationName {
    name = "fö";
    expected = "f-";
  };

  testSanitizeDerivationNameAscii = testSanitizeDerivationName {
    name = " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~";
    expected = "-+--.-0123456789-=-?-ABCDEFGHIJKLMNOPQRSTUVWXYZ-_-abcdefghijklmnopqrstuvwxyz-";
  };

  testSanitizeDerivationNameTooLong = testSanitizeDerivationName {
    name = "This string is loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong";
    expected = "loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong";
  };

  testSanitizeDerivationNameTooLongWithInvalid = testSanitizeDerivationName {
    name = "Hello there aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa &&&&&&&&";
    expected = "there-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-";
  };

  testSanitizeDerivationNameEmpty = testSanitizeDerivationName {
    name = "";
    expected = "unknown";
  };

  testFreeformOptions = {
    expr =
      let
        submodule = { lib, ... }: {
          freeformType = lib.types.attrsOf (lib.types.submodule {
            options.bar = lib.mkOption {};
          });
          options.bar = lib.mkOption {};
        };

        module = { lib, ... }: {
          options.foo = lib.mkOption {
            type = lib.types.submodule submodule;
          };
        };

        options = (evalModules {
          modules = [ module ];
        }).options;

        locs = filter (o: ! o.internal) (optionAttrSetToDocList options);
      in map (o: o.loc) locs;
    expected = [ [ "_module" "args" ] [ "foo" ] [ "foo" "<name>" "bar" ] [ "foo" "bar" ] ];
  };

  testCartesianProductOfEmptySet = {
    expr = cartesianProductOfSets {};
    expected = [ {} ];
  };

  testCartesianProductOfOneSet = {
    expr = cartesianProductOfSets { a = [ 1 2 3 ]; };
    expected = [ { a = 1; } { a = 2; } { a = 3; } ];
  };

  testCartesianProductOfTwoSets = {
    expr = cartesianProductOfSets { a = [ 1 ]; b = [ 10 20 ]; };
    expected = [
      { a = 1; b = 10; }
      { a = 1; b = 20; }
    ];
  };

  testCartesianProductOfTwoSetsWithOneEmpty = {
    expr = cartesianProductOfSets { a = [ ]; b = [ 10 20 ]; };
    expected = [ ];
  };

  testCartesianProductOfThreeSets = {
    expr = cartesianProductOfSets {
      a = [   1   2   3 ];
      b = [  10  20  30 ];
      c = [ 100 200 300 ];
    };
    expected = [
      { a = 1; b = 10; c = 100; }
      { a = 1; b = 10; c = 200; }
      { a = 1; b = 10; c = 300; }

      { a = 1; b = 20; c = 100; }
      { a = 1; b = 20; c = 200; }
      { a = 1; b = 20; c = 300; }

      { a = 1; b = 30; c = 100; }
      { a = 1; b = 30; c = 200; }
      { a = 1; b = 30; c = 300; }

      { a = 2; b = 10; c = 100; }
      { a = 2; b = 10; c = 200; }
      { a = 2; b = 10; c = 300; }

      { a = 2; b = 20; c = 100; }
      { a = 2; b = 20; c = 200; }
      { a = 2; b = 20; c = 300; }

      { a = 2; b = 30; c = 100; }
      { a = 2; b = 30; c = 200; }
      { a = 2; b = 30; c = 300; }

      { a = 3; b = 10; c = 100; }
      { a = 3; b = 10; c = 200; }
      { a = 3; b = 10; c = 300; }

      { a = 3; b = 20; c = 100; }
      { a = 3; b = 20; c = 200; }
      { a = 3; b = 20; c = 300; }

      { a = 3; b = 30; c = 100; }
      { a = 3; b = 30; c = 200; }
      { a = 3; b = 30; c = 300; }
    ];
  };

  # The example from the showAttrPath documentation
  testShowAttrPathExample = {
    expr = showAttrPath [ "foo" "10" "bar" ];
    expected = "foo.\"10\".bar";
  };

  testShowAttrPathEmpty = {
    expr = showAttrPath [];
    expected = "<root attribute path>";
  };

  testShowAttrPathVarious = {
    expr = showAttrPath [
      "."
      "foo"
      "2"
      "a2-b"
      "_bc'de"
    ];
    expected = ''".".foo."2".a2-b._bc'de'';
  };

  testGroupBy = {
    expr = groupBy (n: toString (mod n 5)) (range 0 16);
    expected = {
      "0" = [ 0 5 10 15 ];
      "1" = [ 1 6 11 16 ];
      "2" = [ 2 7 12 ];
      "3" = [ 3 8 13 ];
      "4" = [ 4 9 14 ];
    };
  };

  testGroupBy' = {
    expr = groupBy' builtins.add 0 (x: boolToString (x > 2)) [ 5 1 2 3 4 ];
    expected = { false = 3; true = 12; };
  };

  # The example from the updateManyAttrsByPath documentation
  testUpdateManyAttrsByPathExample = {
    expr = updateManyAttrsByPath [
      {
        path = [ "a" "b" ];
        update = old: { d = old.c; };
      }
      {
        path = [ "a" "b" "c" ];
        update = old: old + 1;
      }
      {
        path = [ "x" "y" ];
        update = old: "xy";
      }
    ] { a.b.c = 0; };
    expected = { a = { b = { d = 1; }; }; x = { y = "xy"; }; };
  };

  # If there are no updates, the value is passed through
  testUpdateManyAttrsByPathNone = {
    expr = updateManyAttrsByPath [] "something";
    expected = "something";
  };

  # A single update to the root path is just like applying the function directly
  testUpdateManyAttrsByPathSingleIncrement = {
    expr = updateManyAttrsByPath [
      {
        path = [ ];
        update = old: old + 1;
      }
    ] 0;
    expected = 1;
  };

  # Multiple updates can be applied are done in order
  testUpdateManyAttrsByPathMultipleIncrements = {
    expr = updateManyAttrsByPath [
      {
        path = [ ];
        update = old: old + "a";
      }
      {
        path = [ ];
        update = old: old + "b";
      }
      {
        path = [ ];
        update = old: old + "c";
      }
    ] "";
    expected = "abc";
  };

  # If an update doesn't use the value, all previous updates are not evaluated
  testUpdateManyAttrsByPathLazy = {
    expr = updateManyAttrsByPath [
      {
        path = [ ];
        update = old: old + throw "nope";
      }
      {
        path = [ ];
        update = old: "untainted";
      }
    ] (throw "start");
    expected = "untainted";
  };

  # Deeply nested attributes can be updated without affecting others
  testUpdateManyAttrsByPathDeep = {
    expr = updateManyAttrsByPath [
      {
        path = [ "a" "b" "c" ];
        update = old: old + 1;
      }
    ] {
      a.b.c = 0;

      a.b.z = 0;
      a.y.z = 0;
      x.y.z = 0;
    };
    expected = {
      a.b.c = 1;

      a.b.z = 0;
      a.y.z = 0;
      x.y.z = 0;
    };
  };

  # Nested attributes are updated first
  testUpdateManyAttrsByPathNestedBeforehand = {
    expr = updateManyAttrsByPath [
      {
        path = [ "a" ];
        update = old: old // { x = old.b; };
      }
      {
        path = [ "a" "b" ];
        update = old: old + 1;
      }
    ] {
      a.b = 0;
    };
    expected = {
      a.b = 1;
      a.x = 1;
    };
  };

  ## Levenshtein distance functions and co.
  testCommonPrefixLengthEmpty = {
    expr = strings.commonPrefixLength "" "hello";
    expected = 0;
  };

  testCommonPrefixLengthSame = {
    expr = strings.commonPrefixLength "hello" "hello";
    expected = 5;
  };

  testCommonPrefixLengthDiffering = {
    expr = strings.commonPrefixLength "hello" "hey";
    expected = 2;
  };

  testCommonSuffixLengthEmpty = {
    expr = strings.commonSuffixLength "" "hello";
    expected = 0;
  };

  testCommonSuffixLengthSame = {
    expr = strings.commonSuffixLength "hello" "hello";
    expected = 5;
  };

  testCommonSuffixLengthDiffering = {
    expr = strings.commonSuffixLength "test" "rest";
    expected = 3;
  };

  testLevenshteinEmpty = {
    expr = strings.levenshtein "" "";
    expected = 0;
  };

  testLevenshteinOnlyAdd = {
    expr = strings.levenshtein "" "hello there";
    expected = 11;
  };

  testLevenshteinOnlyRemove = {
    expr = strings.levenshtein "hello there" "";
    expected = 11;
  };

  testLevenshteinOnlyTransform = {
    expr = strings.levenshtein "abcdef" "ghijkl";
    expected = 6;
  };

  testLevenshteinMixed = {
    expr = strings.levenshtein "kitchen" "sitting";
    expected = 5;
  };

  testLevenshteinAtMostZeroFalse = {
    expr = strings.levenshteinAtMost 0 "foo" "boo";
    expected = false;
  };

  testLevenshteinAtMostZeroTrue = {
    expr = strings.levenshteinAtMost 0 "foo" "foo";
    expected = true;
  };

  testLevenshteinAtMostOneFalse = {
    expr = strings.levenshteinAtMost 1 "car" "ct";
    expected = false;
  };

  testLevenshteinAtMostOneTrue = {
    expr = strings.levenshteinAtMost 1 "car" "cr";
    expected = true;
  };

  # We test levenshteinAtMost 2 particularly well because it uses a complicated
  # implementation
  testLevenshteinAtMostTwoIsEmpty = {
    expr = strings.levenshteinAtMost 2 "" "";
    expected = true;
  };

  testLevenshteinAtMostTwoIsZero = {
    expr = strings.levenshteinAtMost 2 "abcdef" "abcdef";
    expected = true;
  };

  testLevenshteinAtMostTwoIsOne = {
    expr = strings.levenshteinAtMost 2 "abcdef" "abddef";
    expected = true;
  };

  testLevenshteinAtMostTwoDiff0False = {
    expr = strings.levenshteinAtMost 2 "abcdef" "aczyef";
    expected = false;
  };

  testLevenshteinAtMostTwoDiff0Outer = {
    expr = strings.levenshteinAtMost 2 "abcdef" "zbcdez";
    expected = true;
  };

  testLevenshteinAtMostTwoDiff0DelLeft = {
    expr = strings.levenshteinAtMost 2 "abcdef" "bcdefz";
    expected = true;
  };

  testLevenshteinAtMostTwoDiff0DelRight = {
    expr = strings.levenshteinAtMost 2 "abcdef" "zabcde";
    expected = true;
  };

  testLevenshteinAtMostTwoDiff1False = {
    expr = strings.levenshteinAtMost 2 "abcdef" "bddez";
    expected = false;
  };

  testLevenshteinAtMostTwoDiff1DelLeft = {
    expr = strings.levenshteinAtMost 2 "abcdef" "bcdez";
    expected = true;
  };

  testLevenshteinAtMostTwoDiff1DelRight = {
    expr = strings.levenshteinAtMost 2 "abcdef" "zbcde";
    expected = true;
  };

  testLevenshteinAtMostTwoDiff2False = {
    expr = strings.levenshteinAtMost 2 "hello" "hxo";
    expected = false;
  };

  testLevenshteinAtMostTwoDiff2True = {
    expr = strings.levenshteinAtMost 2 "hello" "heo";
    expected = true;
  };

  testLevenshteinAtMostTwoDiff3 = {
    expr = strings.levenshteinAtMost 2 "hello" "ho";
    expected = false;
  };

  testLevenshteinAtMostThreeFalse = {
    expr = strings.levenshteinAtMost 3 "hello" "Holla!";
    expected = false;
  };

  testLevenshteinAtMostThreeTrue = {
    expr = strings.levenshteinAtMost 3 "hello" "Holla";
    expected = true;
  };

  # lazyDerivation

  testLazyDerivationIsLazyInDerivationForAttrNames = {
    expr = attrNames (lazyDerivation {
      derivation = throw "not lazy enough";
    });
    # It's ok to add attribute names here when lazyDerivation is improved
    # in accordance with its inline comments.
    expected = [ "drvPath" "meta" "name" "out" "outPath" "outputName" "outputs" "system" "type" ];
  };

  testLazyDerivationIsLazyInDerivationForPassthruAttr = {
    expr = (lazyDerivation {
      derivation = throw "not lazy enough";
      passthru.tests = "whatever is in tests";
    }).tests;
    expected = "whatever is in tests";
  };

  testLazyDerivationIsLazyInDerivationForPassthruAttr2 = {
    # passthru.tests is not a special case. It works for any attr.
    expr = (lazyDerivation {
      derivation = throw "not lazy enough";
      passthru.foo = "whatever is in foo";
    }).foo;
    expected = "whatever is in foo";
  };

  testLazyDerivationIsLazyInDerivationForMeta = {
    expr = (lazyDerivation {
      derivation = throw "not lazy enough";
      meta = "whatever is in meta";
    }).meta;
    expected = "whatever is in meta";
  };

  testLazyDerivationReturnsDerivationAttrs = let
    derivation = {
      type = "derivation";
      outputs = ["out"];
      out = "test out";
      outPath = "test outPath";
      outputName = "out";
      drvPath = "test drvPath";
      name = "test name";
      system = "test system";
      meta = "test meta";
    };
  in {
    expr = lazyDerivation { inherit derivation; };
    expected = derivation;
  };

  testTypeDescriptionInt = {
    expr = (with types; int).description;
    expected = "signed integer";
  };
  testTypeDescriptionListOfInt = {
    expr = (with types; listOf int).description;
    expected = "list of signed integer";
  };
  testTypeDescriptionListOfListOfInt = {
    expr = (with types; listOf (listOf int)).description;
    expected = "list of list of signed integer";
  };
  testTypeDescriptionListOfEitherStrOrBool = {
    expr = (with types; listOf (either str bool)).description;
    expected = "list of (string or boolean)";
  };
  testTypeDescriptionEitherListOfStrOrBool = {
    expr = (with types; either (listOf bool) str).description;
    expected = "(list of boolean) or string";
  };
  testTypeDescriptionEitherStrOrListOfBool = {
    expr = (with types; either str (listOf bool)).description;
    expected = "string or list of boolean";
  };
  testTypeDescriptionOneOfListOfStrOrBool = {
    expr = (with types; oneOf [ (listOf bool) str ]).description;
    expected = "(list of boolean) or string";
  };
  testTypeDescriptionOneOfListOfStrOrBoolOrNumber = {
    expr = (with types; oneOf [ (listOf bool) str number ]).description;
    expected = "(list of boolean) or string or signed integer or floating point number";
  };
  testTypeDescriptionEitherListOfBoolOrEitherStringOrNumber = {
    expr = (with types; either (listOf bool) (either str number)).description;
    expected = "(list of boolean) or string or signed integer or floating point number";
  };
  testTypeDescriptionEitherEitherListOfBoolOrStringOrNumber = {
    expr = (with types; either (either (listOf bool) str) number).description;
    expected = "(list of boolean) or string or signed integer or floating point number";
  };
  testTypeDescriptionEitherNullOrBoolOrString = {
    expr = (with types; either (nullOr bool) str).description;
    expected = "null or boolean or string";
  };
  testTypeDescriptionEitherListOfEitherBoolOrStrOrInt = {
    expr = (with types; either (listOf (either bool str)) int).description;
    expected = "(list of (boolean or string)) or signed integer";
  };
  testTypeDescriptionEitherIntOrListOrEitherBoolOrStr = {
    expr = (with types; either int (listOf (either bool str))).description;
    expected = "signed integer or list of (boolean or string)";
  };
}