solution 4.4: helper functions and unit tests, step2

README.md

@@ -9,6 +9,9 @@ Answers to [openfullstack.com](https://fullstackopen.com) course exercises from
 - [Exercises 4.1.-4.2.](https://fullstackopen.com/en/part4/structure_of_backend_application_introduction_to_testing#exercises-4-1-4-2)
   _Details solutions: [4.1](https://github.com/patchamama/fullstackopen-part4-bloglist/commit/01104c7798ad53f35ee73994826f5cc3602b9b3e) | [4.2](https://github.com/patchamama/fullstackopen-part4-bloglist/commit/7c913309759236084783f4bdfdec443c5b9e19d5)_
 
+- [Exercises 4.3.-4.7.](https://fullstackopen.com/en/part4/structure_of_backend_application_introduction_to_testing#exercises-4-3-4-7)
+  _Details solutions: [4.3](https://github.com/patchamama/fullstackopen-part4-bloglist/commit/0f1a759e78310de711531ed481917496e2f50ec8) | [4.4]() | [4.5]() | [4.6]() | [4.7]()_
+
 ### b. Testing the backend
 
 ### c. User administration

tests/blog.test.js

@@ -1,9 +1,85 @@
 const listHelper = require('../utils/list_helper')
 
-// describe('test arrays', () => {
 test('dummy returns one', () => {
   const blogs = []
 
   const result = listHelper.dummy(blogs)
   expect(result).toBe(1)
 })
+
+describe('total likes', () => {
+  test('of empty list is zero', () => {
+    const blogs = []
+    const result = listHelper.totalLikes(blogs)
+    expect(result).toBe(0)
+  })
+
+  test('when list has only one blog equals the likes of that', () => {
+    const blogs = [
+      {
+        _id: '23234323242dssfsf',
+        title: 'Test 2nd blog title',
+        author: 'Test of blog author',
+        url: 'Test of blog url ',
+        likes: 6,
+      },
+    ]
+    const result = listHelper.totalLikes(blogs)
+    expect(result).toBe(6)
+  })
+
+  test('of a bigger list is calculated right', () => {
+    const blogs = [
+      {
+        _id: '5a422a851b54a676234d17f7',
+        title: 'React patterns',
+        author: 'Michael Chan',
+        url: 'https://reactpatterns.com/',
+        likes: 7,
+        __v: 0,
+      },
+      {
+        _id: '5a422aa71b54a676234d17f8',
+        title: 'Go To Statement Considered Harmful',
+        author: 'Edsger W. Dijkstra',
+        url: 'http://www.u.arizona.edu/~rubinson/copyright_violations/Go_To_Considered_Harmful.html',
+        likes: 5,
+        __v: 0,
+      },
+      {
+        _id: '5a422b3a1b54a676234d17f9',
+        title: 'Canonical string reduction',
+        author: 'Edsger W. Dijkstra',
+        url: 'http://www.cs.utexas.edu/~EWD/transcriptions/EWD08xx/EWD808.html',
+        likes: 12,
+        __v: 0,
+      },
+      {
+        _id: '5a422b891b54a676234d17fa',
+        title: 'First class tests',
+        author: 'Robert C. Martin',
+        url: 'http://blog.cleancoder.com/uncle-bob/2017/05/05/TestDefinitions.htmll',
+        likes: 10,
+        __v: 0,
+      },
+      {
+        _id: '5a422ba71b54a676234d17fb',
+        title: 'TDD harms architecture',
+        author: 'Robert C. Martin',
+        url: 'http://blog.cleancoder.com/uncle-bob/2017/03/03/TDD-Harms-Architecture.html',
+        likes: 0,
+        __v: 0,
+      },
+      {
+        _id: '5a422bc61b54a676234d17fc',
+        title: 'Type wars',
+        author: 'Robert C. Martin',
+        url: 'http://blog.cleancoder.com/uncle-bob/2016/05/01/TypeWars.html',
+        likes: 2,
+        __v: 0,
+      },
+    ]
+    const result = listHelper.totalLikes(blogs)
+    expect(result).toBe(36)
+  })
+})

utils/list_helper.js

@@ -3,6 +3,14 @@ const dummy = (blogs) => {
   return 1
 }
 
+const totalLikes = (blogs) => {
+  const reducer = (sum, item) => {
+    return sum + item.likes
+  }
+  return blogs.length === 0 ? 0 : blogs.reduce(reducer, 0)
+}
+
 module.exports = {
   dummy,
+  totalLikes,
 }