add hint tests

Author: ShMcK

src/modules/editor/reducer.test.ts

@@ -1,4 +1,5 @@
 /// <reference path="../../typings/globals/jest/index.d.ts" />
+
 import reducer from './reducer';
 import * as types from './types';
 

src/modules/hints/index.ts

@@ -1,5 +1,10 @@
 import {HINT_POSITION_SET} from './types';
-
+/**
+ * sets hint index
+ * @param  {} hintPosition=0
+ * @param  {Action} action
+ * @returns number
+ */
 export default function hintPositionReducer(
   hintPosition = 0, action: Action
 ): number {

src/modules/hints/reducer.test.ts

@@ -0,0 +1,19 @@
+/// <reference path="../../typings/globals/jest/index.d.ts" />
+
+import reducer from './index';
+import { HINT_POSITION_SET } from './types';
+
+describe('hint reducer', () => {
+
+  it('should do nothing if no triggered action type', () => {
+    const action = { type: 'unknown' };
+    expect(reducer(undefined, action)).toBe(0);
+  });
+
+  it('should handle HINT_POSITION_SET', () => {
+    const hintPosition = 2;
+    const action = { type: HINT_POSITION_SET, payload: { hintPosition } };
+    expect(reducer(0, action)).toBe(hintPosition);
+  });
+
+});