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/reverse.js

@@ -0,0 +1,94 @@
+import assert from 'assert';
+import lodashStable from 'lodash';
+import { LARGE_ARRAY_SIZE, identity } from './utils.js';
+import reverse from '../reverse.js';
+import compact from '../compact.js';
+import head from '../head.js';
+
+describe('reverse', function() {
+  var largeArray = lodashStable.range(LARGE_ARRAY_SIZE).concat(null),
+      smallArray = [0, 1, 2, null];
+
+  it('should reverse `array`', function() {
+    var array = [1, 2, 3],
+        actual = reverse(array);
+
+    assert.strictEqual(actual, array);
+    assert.deepStrictEqual(array, [3, 2, 1]);
+  });
+
+  it('should return the wrapped reversed `array`', function() {
+    lodashStable.times(2, function(index) {
+      var array = (index ? largeArray : smallArray).slice(),
+          clone = array.slice(),
+          wrapped = _(array).reverse(),
+          actual = wrapped.value();
+
+      assert.ok(wrapped instanceof _);
+      assert.strictEqual(actual, array);
+      assert.deepStrictEqual(actual, clone.slice().reverse());
+    });
+  });
+
+  it('should work in a lazy sequence', function() {
+    lodashStable.times(2, function(index) {
+      var array = (index ? largeArray : smallArray).slice(),
+          expected = array.slice(),
+          actual = _(array).slice(1).reverse().value();
+
+      assert.deepStrictEqual(actual, expected.slice(1).reverse());
+      assert.deepStrictEqual(array, expected);
+    });
+  });
+
+  it('should be lazy when in a lazy sequence', function() {
+    var spy = {
+      'toString': function() {
+        throw new Error('spy was revealed');
+      }
+    };
+
+    var array = largeArray.concat(spy),
+        expected = array.slice();
+
+    try {
+      var wrapped = _(array).slice(1).map(String).reverse(),
+          actual = wrapped.last();
+    } catch (e) {}
+
+    assert.ok(wrapped instanceof _);
+    assert.strictEqual(actual, '1');
+    assert.deepEqual(array, expected);
+  });
+
+  it('should work in a hybrid sequence', function() {
+    lodashStable.times(2, function(index) {
+      var clone = (index ? largeArray : smallArray).slice();
+
+      lodashStable.each(['map', 'filter'], function(methodName) {
+        var array = clone.slice(),
+            expected = clone.slice(1, -1).reverse(),
+            actual = _(array)[methodName](identity).thru(compact).reverse().value();
+
+        assert.deepStrictEqual(actual, expected);
+
+        array = clone.slice();
+        actual = _(array).thru(compact)[methodName](identity).pull(1).push(3).reverse().value();
+
+        assert.deepStrictEqual(actual, [3].concat(expected.slice(0, -1)));
+      });
+    });
+  });
+
+  it('should track the `__chain__` value of a wrapper', function() {
+    lodashStable.times(2, function(index) {
+      var array = (index ? largeArray : smallArray).slice(),
+          expected = array.slice().reverse(),
+          wrapped = _(array).chain().reverse().head();
+
+      assert.ok(wrapped instanceof _);
+      assert.strictEqual(wrapped.value(), head(expected));
+      assert.deepStrictEqual(array, expected);
+    });
+  });
+});