wip: code formatting nits continued

test/countBy.spec.js

@@ -0,0 +1,53 @@
+import lodashStable from 'lodash';
+import countBy from '../src/countBy';
+
+describe('countBy', () => {
+    const array = [6.1, 4.2, 6.3];
+
+    it('should transform keys by `iteratee`', () => {
+        const actual = countBy(array, Math.floor);
+        expect(actual).toEqual({ 4: 1, 6: 2 });
+    });
+
+    it('should use `_.identity` when `iteratee` is nullish', () => {
+        const array = [4, 6, 6];
+        const values = [, null, undefined];
+        const expected = lodashStable.map(values, lodashStable.constant({ 4: 1, 6: 2 }));
+
+        const actual = lodashStable.map(values, (value, index) =>
+            index ? countBy(array, value) : countBy(array),
+        );
+
+        expect(actual).toEqual(expected);
+    });
+
+    it('should work with `_.property` shorthands', () => {
+        const actual = countBy(['one', 'two', 'three'], 'length');
+        expect(actual).toEqual({ 3: 2, 5: 1 });
+    });
+
+    it('should only add values to own, not inherited, properties', () => {
+        const actual = countBy(array, (n) =>
+            Math.floor(n) > 4 ? 'hasOwnProperty' : 'constructor',
+        );
+
+        expect(actual.constructor).toEqual(1);
+        expect(actual.hasOwnProperty).toEqual(2);
+    });
+
+    it('should work with a number for `iteratee`', () => {
+        const array = [
+            [1, 'a'],
+            [2, 'a'],
+            [2, 'b'],
+        ];
+
+        expect(countBy(array, 0)).toEqual({ 1: 1, 2: 2 });
+        expect(countBy(array, 1)).toEqual({ a: 2, b: 1 });
+    });
+
+    it('should work with an object for `collection`', () => {
+        const actual = countBy({ a: 6.1, b: 4.2, c: 6.3 }, Math.floor);
+        expect(actual).toEqual({ 4: 1, 6: 2 });
+    });
+});