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/lodash(...).plant.js

@@ -0,0 +1,39 @@
+import assert from 'assert';
+import lodashStable from 'lodash';
+import { square, isNpm } from './utils.js';
+import compact from '../compact.js';
+
+describe('lodash(...).plant', function() {
+  it('should clone the chained sequence planting `value` as the wrapped value', function() {
+    var array1 = [5, null, 3, null, 1],
+        array2 = [10, null, 8, null, 6],
+        wrapped1 = _(array1).thru(compact).map(square).takeRight(2).sort(),
+        wrapped2 = wrapped1.plant(array2);
+
+    assert.deepEqual(wrapped2.value(), [36, 64]);
+    assert.deepEqual(wrapped1.value(), [1, 9]);
+  });
+
+  it('should clone `chainAll` settings', function() {
+    var array1 = [2, 4],
+        array2 = [6, 8],
+        wrapped1 = _(array1).chain().map(square),
+        wrapped2 = wrapped1.plant(array2);
+
+    assert.deepEqual(wrapped2.head().value(), 36);
+  });
+
+  it('should reset iterator data on cloned sequences', function() {
+    if (!isNpm && Symbol && Symbol.iterator) {
+      var array1 = [2, 4],
+          array2 = [6, 8],
+          wrapped1 = _(array1).map(square);
+
+      assert.deepStrictEqual(lodashStable.toArray(wrapped1), [4, 16]);
+      assert.deepStrictEqual(lodashStable.toArray(wrapped1), []);
+
+      var wrapped2 = wrapped1.plant(array2);
+      assert.deepStrictEqual(lodashStable.toArray(wrapped2), [36, 64]);
+    }
+  });
+});