added productList init tests

lib/ProductList/ProductList.js

@@ -75,6 +75,12 @@ class ProductList {
       });
   }
 
+  /**
+   * Initializes the product list with the cached data or latest ones if missing
+   * or outdated.
+   * 
+   * @returns {Promise.<boolean>}
+   */
   init() {
     return this._temp.get()
       .then(data => {
@@ -89,7 +95,7 @@ class ProductList {
           return this.loadProducts();
         }
         else {
-          return true;
+          return Promise.resolve(true);
         }
       });
   }
@@ -99,6 +105,7 @@ class ProductList {
    * 
    * @param {Object} products - The raw data of the product list with meta
    *   information.
+   * @returns {boolean}
    */
   _parseData(products) {
     if (!products) {

test/ProductList/ProductList.test.js

@@ -0,0 +1,67 @@
+const ProductList = require('../../lib/ProductList');
+
+describe('ProductList', () => {
+  describe('init', () => {
+    const productList = new ProductList({ client: {} });
+
+    productList.loadProducts = sinon.stub().returns(Promise.resolve('LOADING'));
+
+    const data = {
+      date: '2018-03-01',
+      salesProductList: {
+        SalesProduct: []
+      }
+    };
+
+    beforeEach(() => {
+      productList.loadProducts.resetHistory();
+    });
+
+    it('should trigger load products if data are not available', done => {
+      productList._temp = {
+        get: sinon.stub().returns(Promise.resolve(''))
+      };
+
+      productList.init()
+        .then(result => {
+          productList._temp.get.calledOnce.should.be.true();
+          productList.loadProducts.calledOnce.should.be.true();
+
+          result.should.equal('LOADING');
+
+          done();
+        });
+    });
+
+    it('should load products if data are too old', done => {
+      productList._temp = {
+        get: sinon.stub().returns(Promise.resolve(JSON.stringify(data)))
+      };
+
+      productList.init()
+        .then(result => {
+          productList._temp.get.calledOnce.should.be.true();
+          productList.loadProducts.calledOnce.should.be.true();
+
+          result.should.equal('LOADING');
+
+          done();
+        });
+    });
+
+    xit('should take data if available', done => {
+      // TODO: manipulate date
+      productList._temp = {
+        get: sinon.stub().returns(Promise.resolve(JSON.stringify(data)))
+      };
+
+      productList.init()
+        .then(result => {
+          productList._temp.get.calledOnce.should.be.true();
+          productList.loadProducts.calledOnce.should.be.false();
+
+          done();
+        });
+    });
+  });
+});