test(index): add tests for index

tests/index.test.js

@@ -0,0 +1,12 @@
+import * as o from '../src/index';
+
+describe('index', () => {
+  test('should return 24 functions', () => {
+    expect(Object.keys(o).length).toBe(25);
+  });
+
+  test('all functions are typeof function', () => {
+    const reducer = (last, current) => last && typeof current === 'function';
+    expect(Object.values(o).reduce(reducer)).toBe(true);
+  });
+});