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/zipObject-methods.js

@@ -0,0 +1,39 @@
+import assert from 'assert';
+import lodashStable from 'lodash';
+import { _, LARGE_ARRAY_SIZE, square, isEven } from './utils.js';
+
+describe('zipObject methods', function() {
+  lodashStable.each(['zipObject', 'zipObjectDeep'], function(methodName) {
+    var func = _[methodName],
+        object = { 'barney': 36, 'fred': 40 },
+        isDeep = methodName == 'zipObjectDeep';
+
+    it('`_.' + methodName + '` should zip together key/value arrays into an object', function() {
+      var actual = func(['barney', 'fred'], [36, 40]);
+      assert.deepStrictEqual(actual, object);
+    });
+
+    it('`_.' + methodName + '` should ignore extra `values`', function() {
+      assert.deepStrictEqual(func(['a'], [1, 2]), { 'a': 1 });
+    });
+
+    it('`_.' + methodName + '` should assign `undefined` values for extra `keys`', function() {
+      assert.deepStrictEqual(func(['a', 'b'], [1]), { 'a': 1, 'b': undefined });
+    });
+
+    it('`_.' + methodName + '` should ' + (isDeep ? '' : 'not ') + 'support deep paths', function() {
+      lodashStable.each(['a.b.c', ['a', 'b', 'c']], function(path, index) {
+        var expected = isDeep ? ({ 'a': { 'b': { 'c': 1 } } }) : (index ? { 'a,b,c': 1 } : { 'a.b.c': 1 });
+        assert.deepStrictEqual(func([path], [1]), expected);
+      });
+    });
+
+    it('`_.' + methodName + '` should work in a lazy sequence', function() {
+      var values = lodashStable.range(LARGE_ARRAY_SIZE),
+          props = lodashStable.map(values, function(value) { return 'key' + value; }),
+          actual = _(props)[methodName](values).map(square).filter(isEven).take().value();
+
+      assert.deepEqual(actual, _.take(_.filter(_.map(func(props, values), square), isEven)));
+    });
+  });
+});