jest

src/consts.test.js

@@ -0,0 +1,7 @@
+import {DIFFICULTY, START_BUTTON_EASY_ID} from './consts';
+
+describe('getDifficultyById', () => {
+    it('should return correct difficulty', () => {
+        expect(DIFFICULTY[START_BUTTON_EASY_ID]).toBe(10);
+    });
+});

src/script.js

@@ -130,7 +130,7 @@ const getExample = () => {
 
 };
 
-const getDifficultyById = id => {
+export const getDifficultyById = id => {
     return DIFFICULTY[id];
 };