node-tests

Testing Applications (Code testing & Debugging) Mocha Basic Testing Watch and Auto Restart Tests Using Assertion Library Testing Assertion Library Testing Asynchronous Code Testing Express Applications Organizing Test with Describe() Test Spies

Mocha and Basic Testing
    - Setting up test cases
    - Verify program is doing what it says
    - Process
        - New directory
        - npm init
        - Open directory in text editor - node-tests
        - utils folder in node-tests
        - utils.js in utils
        - Adding function added
    - Using Mocha framework
        - mochajs.org
        - npm install mocha --save-dev
            - --save-dev saves module for development purposes only!
        - Create 'utils.test.js' - .test.js is test file
        - Create test case using 'it('string', function(){});' function
            - First string arg is what the test should do
            - Function should include code to test add function
                -   var res = utils.add(33,11);
        - Import utils
        - Adjust package.json for testing
            -   'scripts': {
                    'test': 'mocha **/*.js.test'
                },
                - Uses mocha to run any file with .js.test extension
        - Run tests with 'npm test'
            - Test only fails if error is thrown

Watch and Auto Restart Test
    - nodemon normall runs app.js
    - Can run any commmands using nodemon --exec 'npm test'
    - Can create npm command in package.json
        -   "scripts": {
                ...
                "test-watch": "nodemon --exec 'npm test'"
            }
        - run with 'npm run test-watch'

Using an Assertion Library
    - Let us make assertions about functions, test those assertions
    - Expect by mjackson
        - expect(value).toExist(); --> Value is truthy
        - expect(value).toBe(); --> Equals
        - expect(value).toBeA(string) --> to be a type defined by string
        - See other assertions on web page
        - Can chain assertions, too.

Testing Asyncronous Code
    - Not much different.
    - Add done parameter to it() function argument, call when assertions should be made
        -   it('should async add two numbers', (done) => {
                utils.asyncAdd(4, 3, (sum) => {
                    expect(sum).toBe(7).toBeA('number');
                    done();
                });
            });

Testing Express Applications - Part I
    - Setting up an Express app to be tested in the next section

Testing Express Applications - Part II
    - Using Supertest to test Express
        - Built by same people who built Express
        - Should make testing Express super simple
    - Install using 'npm i supertest --save-dev'
    - Create server.test.js file
    - Import using require('supertest');
    - Import Express app
        -   module.exports.app = app; // in Express app file
        -   var app = require('./appfile.js').app // in test file
    - Use mocha to initiate test, use Supertest to make assertions
        -   request(app)                // make a request to the app
                .get('/')               // get home index
                .expect(200)            // number refers to status code
                .expect('hello world')  // string refers to response body
                .end(done);             // ends both supertest and mocha 
                                        // tests
                
        -   require('expect'); to make
                .expect((res) => {
                    expect(res.body).toInclude({
                        error: 'Page not found.'
                    })
                }) // Assert body content

Organizing Tests With describe()
    - should group together tests
    - describe(string, callback)
        - string names the block of tests
        - callback contains the related tests
        - can be nested to form subsets

Test Spies
    - Spies let you swap out a real function for a testing utility
        -   var spy = expect.createSpy()
        -   expect(spy).assertions...
                - toHaveBeenCalled()
                - toHaveBeenCalledWith()
    - To test functions used in test files, going to use rewire
        - Install and load in normally
        - Use rewire instead of require when loading in the file you want to mock out
        -   var app = rewire('./app');
        - addss app.__get__ and app.__set__ functions
        -   var db = {
                saveUser: expect.createSpy()
            };
            app.__set__)('db', db);
        -   it('should call saveUser with user object', () => {
                var email = 'disruptive@example.com';
                var password = '123abc';

                app.handleSignup(email, password);
                expect(db.saveUser).toHaveBeenCalledWith({email, password});
            });