wip: code formatting nits continued

test/sumBy.spec.js

@@ -0,0 +1,29 @@
+import { slice } from './utils';
+import sumBy from '../src/sumBy';
+
+describe('sumBy', () => {
+    const array = [6, 4, 2];
+    const objects = [{ a: 2 }, { a: 3 }, { a: 1 }];
+
+    it('should work with an `iteratee`', () => {
+        const actual = sumBy(objects, (object) => object.a);
+
+        expect(actual).toEqual(6);
+    });
+
+    it('should provide correct `iteratee` arguments', () => {
+        let args;
+
+        sumBy(array, function () {
+            args || (args = slice.call(arguments));
+        });
+
+        expect(args).toEqual([6]);
+    });
+
+    it('should work with `_.property` shorthands', () => {
+        const arrays = [[2], [3], [1]];
+        expect(sumBy(arrays, 0)).toBe(6);
+        expect(sumBy(objects, 'a')).toBe(6);
+    });
+});