Add initial test files from lodash v4. (#4172)

* Install test dependencies.

* Add initial test files.

These files were created using a simplistic AST manipulator using `recast` to
preserve formatting. There's bound to be a huge chunk of errors, but this serves
as a good start. QUnit was replaced with Mocha, with ES2015 imports running via
`esm`.

As far as possible, QUnit-specific syntax has been replaced with Mocha's
`describe` and `it`, while the native Node.js `assert` module is used for
assertions. Files in the `test` directory ending in `.test.js` will be treated
as test files.

* Add initial passing files to test run.

test/unzip-and-zip.js

@@ -0,0 +1,72 @@
+import assert from 'assert';
+import lodashStable from 'lodash';
+import { _, falsey, stubArray } from './utils.js';
+
+describe('unzip and zip', function() {
+  lodashStable.each(['unzip', 'zip'], function(methodName, index) {
+    var func = _[methodName];
+    func = lodashStable.bind(index ? func.apply : func.call, func, null);
+
+    var object = {
+      'an empty array': [
+        [],
+        []
+      ],
+      '0-tuples': [
+        [[], []],
+        []
+      ],
+      '2-tuples': [
+        [['barney', 'fred'], [36, 40]],
+        [['barney', 36], ['fred', 40]]
+      ],
+      '3-tuples': [
+        [['barney', 'fred'], [36, 40], [false, true]],
+        [['barney', 36, false], ['fred', 40, true]]
+      ]
+    };
+
+    lodashStable.forOwn(object, function(pair, key) {
+      it('`_.' + methodName + '` should work with ' + key, function() {
+        var actual = func(pair[0]);
+        assert.deepStrictEqual(actual, pair[1]);
+        assert.deepStrictEqual(func(actual), actual.length ? pair[0] : []);
+      });
+    });
+
+    it('`_.' + methodName + '` should work with tuples of different lengths', function() {
+      var pair = [
+        [['barney', 36], ['fred', 40, false]],
+        [['barney', 'fred'], [36, 40], [undefined, false]]
+      ];
+
+      var actual = func(pair[0]);
+      assert.ok('0' in actual[2]);
+      assert.deepStrictEqual(actual, pair[1]);
+
+      actual = func(actual);
+      assert.ok('2' in actual[0]);
+      assert.deepStrictEqual(actual, [['barney', 36, undefined], ['fred', 40, false]]);
+    });
+
+    it('`_.' + methodName + '` should treat falsey values as empty arrays', function() {
+      var expected = lodashStable.map(falsey, stubArray);
+
+      var actual = lodashStable.map(falsey, function(value) {
+        return func([value, value, value]);
+      });
+
+      assert.deepStrictEqual(actual, expected);
+    });
+
+    it('`_.' + methodName + '` should ignore values that are not arrays or `arguments` objects', function() {
+      var array = [[1, 2], [3, 4], null, undefined, { '0': 1 }];
+      assert.deepStrictEqual(func(array), [[1, 3], [2, 4]]);
+    });
+
+    it('`_.' + methodName + '` should support consuming its return value', function() {
+      var expected = [['barney', 'fred'], [36, 40]];
+      assert.deepStrictEqual(func(func(func(func(expected)))), expected);
+    });
+  });
+});