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/inRange.js

@@ -0,0 +1,54 @@
+import assert from 'assert';
+import lodashStable from 'lodash';
+import { falsey, stubTrue } from './utils.js';
+import inRange from '../inRange.js';
+
+describe('inRange', function() {
+  it('should work with an `end`', function() {
+    assert.strictEqual(inRange(3, 5), true);
+    assert.strictEqual(inRange(5, 5), false);
+    assert.strictEqual(inRange(6, 5), false);
+  });
+
+  it('should work with a `start` and `end`', function() {
+    assert.strictEqual(inRange(1, 1, 5), true);
+    assert.strictEqual(inRange(3, 1, 5), true);
+    assert.strictEqual(inRange(0, 1, 5), false);
+    assert.strictEqual(inRange(5, 1, 5), false);
+  });
+
+  it('should treat falsey `start` as `0`', function() {
+    lodashStable.each(falsey, function(value, index) {
+      if (index) {
+        assert.strictEqual(inRange(0, value), false);
+        assert.strictEqual(inRange(0, value, 1), true);
+      } else {
+        assert.strictEqual(inRange(0), false);
+      }
+    });
+  });
+
+  it('should swap `start` and `end` when `start` > `end`', function() {
+    assert.strictEqual(inRange(2, 5, 1), true);
+    assert.strictEqual(inRange(-3, -2, -6), true);
+  });
+
+  it('should work with a floating point `n` value', function() {
+    assert.strictEqual(inRange(0.5, 5), true);
+    assert.strictEqual(inRange(1.2, 1, 5), true);
+    assert.strictEqual(inRange(5.2, 5), false);
+    assert.strictEqual(inRange(0.5, 1, 5), false);
+  });
+
+  it('should coerce arguments to finite numbers', function() {
+    var actual = [
+      inRange(0, '1'),
+      inRange(0, '0', 1),
+      inRange(0, 0, '1'),
+      inRange(0, NaN, 1),
+      inRange(-1, -1, NaN)
+    ];
+
+    assert.deepStrictEqual(actual, lodashStable.map(actual, stubTrue));
+  });
+});