wip: code formatting nits continued

test/invertBy.spec.js

@@ -0,0 +1,42 @@
+import lodashStable from 'lodash';
+import invertBy from '../src/invertBy';
+
+describe('invertBy', () => {
+    const object = { a: 1, b: 2, c: 1 };
+
+    it('should transform keys by `iteratee`', () => {
+        const expected = { group1: ['a', 'c'], group2: ['b'] };
+
+        const actual = invertBy(object, (value) => `group${value}`);
+
+        expect(actual).toEqual(expected);
+    });
+
+    it('should use `_.identity` when `iteratee` is nullish', () => {
+        const values = [, null, undefined];
+        const expected = lodashStable.map(
+            values,
+            lodashStable.constant({ 1: ['a', 'c'], 2: ['b'] }),
+        );
+
+        const actual = lodashStable.map(values, (value, index) =>
+            index ? invertBy(object, value) : invertBy(object),
+        );
+
+        expect(actual).toEqual(expected);
+    });
+
+    it('should only add multiple values to own, not inherited, properties', () => {
+        const object = { a: 'hasOwnProperty', b: 'constructor' };
+        const expected = { hasOwnProperty: ['a'], constructor: ['b'] };
+
+        expect(lodashStable.isEqual(invertBy(object), expected))
+    });
+
+    it('should return a wrapped value when chaining', () => {
+        const wrapped = _(object).invertBy();
+
+        expect(wrapped instanceof _)
+        expect(wrapped.value(), { 1: ['a', 'c']).toEqual(2: ['b'] });
+    });
+});