Testing NodeJS

Testing Patterns

• Unit: Small tests covering individual functions.
• Integration: Integrated modules(combined functionality).
• Functional: Focused on end result of larger actions.
• Acceptance: Typically client-side, end-to-end testing.

JavaScript Testing Frameworks

• jasmine
• karma
• expresso
• mocha
• node-tap
• intern
• node-unit
• vows
• node-qunit
• More...

MOCHA 

http://mochajs.org/

Mocha is used to unit test nodeJS applications.

MOCHA Setup

-install mocha as a development dependency for project

-Update package.json

Asynchronous Testing

Basic Tests and Assertions

assert.equal: check more or less equal

assert.strictEqual: exactly equal in type and value

Running the Test

Assertion Methods

• equal: Asserts non-strict equality (==) of actual and expected.
• strictEqual: Asserts strict equality (===) of actual and expected.
• deepEqual: Asserts that actual is deeply equal to expected.
• isOk: Asserts that object is truthy. 
• isNull: Asserts that value is null.
• isTrue: Asserts that value is true.
• fail: Throw a failure. Node.js assert module-compatible.
• match: Asserts that value matches the regular expression regexp.
• throws: Asserts that function will throw an error that is an instance of constructor, or alternately that it will throw an error with message matching regexp.

Testing Tips

• Keep your modules small.
• Be sure to test success AND error cases.
• Test expected AND unexpected data.
• Don't forget that modules are cached.

Testing with Mocks

• Use mocha to test javascript code. Invoke the command mocha to start the tests.
• Use chai for assertions.
• If we find any problematic code then use sinon to spy or stub them to see/ control the behaviour of the functions.
• Use nock to mock servers to prevent making any http calls to the outside environment.
• Use rewire to set/ get variables/external dependencies in the javascript file.
• Use istanbul to calculate the code coverage done by these unit tests.