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/isArrayLike.test.js

@@ -0,0 +1,48 @@
+import assert from 'assert';
+import lodashStable from 'lodash';
+import { args, stubTrue, falsey, asyncFunc, genFunc, slice, symbol, realm } from './utils.js';
+import isArrayLike from '../isArrayLike.js';
+
+describe('isArrayLike', function() {
+  it('should return `true` for array-like values', function() {
+    var values = [args, [1, 2, 3], { '0': 'a', 'length': 1 }, 'a'],
+        expected = lodashStable.map(values, stubTrue),
+        actual = lodashStable.map(values, isArrayLike);
+
+    assert.deepStrictEqual(actual, expected);
+  });
+
+  it('should return `false` for non-arrays', function() {
+    var expected = lodashStable.map(falsey, function(value) {
+      return value === '';
+    });
+
+    var actual = lodashStable.map(falsey, function(value, index) {
+      return index ? isArrayLike(value) : isArrayLike();
+    });
+
+    assert.deepStrictEqual(actual, expected);
+
+    assert.strictEqual(isArrayLike(true), false);
+    assert.strictEqual(isArrayLike(new Date), false);
+    assert.strictEqual(isArrayLike(new Error), false);
+    assert.strictEqual(isArrayLike(_), false);
+    assert.strictEqual(isArrayLike(asyncFunc), false);
+    assert.strictEqual(isArrayLike(genFunc), false);
+    assert.strictEqual(isArrayLike(slice), false);
+    assert.strictEqual(isArrayLike({ 'a': 1 }), false);
+    assert.strictEqual(isArrayLike(1), false);
+    assert.strictEqual(isArrayLike(/x/), false);
+    assert.strictEqual(isArrayLike(symbol), false);
+  });
+
+  it('should work with an array from another realm', function() {
+    if (realm.object) {
+      var values = [realm.arguments, realm.array, realm.string],
+          expected = lodashStable.map(values, stubTrue),
+          actual = lodashStable.map(values, isArrayLike);
+
+      assert.deepStrictEqual(actual, expected);
+    }
+  });
+});