unit test in node js - test cases in node
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Unit testing refers to testing individual units or components of a Node.js application using frameworks like Jest, Mocha, and Chai. Tests reduce bugs, allow safe refactoring, and give confidence. Popular frameworks include Jest, Mocha, and Chai. Unit tests should test isolated parts of a program, be fast, isolated, repeatable, self-validating, and written before code. Async behavior requires adding a callback to wait for asynchronous functions to complete. Tools like Sinon can stub dependencies to avoid external connections during testing.
![Exercise: Write some tests
● Create a new node module (mkdir unit-test && npm init -y)
● Install devDeps (npm i --save-dev jest)
● Configure an “npm test” command
● Test these cases:
○ Sum Number -> returns a + b
○ Subtract Number -> returns a - b
○ Clone Array -> returns […array]
function isEven(n) { let
e = n % 2
if (Number.isNaN(e)) throw Error('Not a number!')
return !e
}
Gist](https://image.slidesharecdn.com/unittestsinnode-160915090519-240414182350-76e68924/85/unit-test-in-node-js-test-cases-in-node-9-320.jpg)
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unit test in node js - test cases in node
- 1. Node.js Unit Tests Nilkanth Shet Shirodkar Software Engineer
- 2. Why test? ● Tests Reduce Bugs ● Tests are good documentation ● Tests allow safe refactoring ● Tests reduce the cost of change ● Testing forces you to think ● Tests gives confidence ● Tests reduce fear!
- 3. Unit Tests ● Isolate each part of the program ● Show that the individual parts are correct Integration Tests ● Test the inter-operation of multiple subsystems ● Test that “the nuts fit the bolts”
- 4. What is NodeJS Unit Testing? NodeJS unit testing refers to testing individual units or components of a Node.js application using specialized automation testing frameworks and libraries. Popular NodeJS unit testing frameworks include Jest, Mocha, and Chai.
- 5. chai vs jest vs mocha Jest, Mocha and Chai have gained significant popularity based on usage and monthly downloads, according to Github and npmtrends, https://npmtrends.com/chai-vs-jest-vs-mocha
- 6. Jest unit test setup config run
- 7. Jest.js setup config run npm init -y npm I –save-dev jest Package.json "scripts": { "test": "jest" } "scripts": { "test": "jest --coverage" } npm test
- 8. Jest.js - assertions ● expect( <this> ).toBe.<assertion>(that) ● Throws an Error if the assertion is false! Examples: ● expect(sum(1, 2)).toBe(3) ● expect(subtract(1, 2)).toBe(-1) ● expect(cloneArray(array)).not.toBe(array) ● expect(cloneArray(array)).toEqual(array) // deep equality
- 9. Exercise: Write some tests ● Create a new node module (mkdir unit-test && npm init -y) ● Install devDeps (npm i --save-dev jest) ● Configure an “npm test” command ● Test these cases: ○ Sum Number -> returns a + b ○ Subtract Number -> returns a - b ○ Clone Array -> returns […array] function isEven(n) { let e = n % 2 if (Number.isNaN(e)) throw Error('Not a number!') return !e } Gist
- 11. Unit tests should come FIRST! ● Fast - 1K+ per second ● Isolated - Perform no I/O ● Repeatable - Run in any order, without intervention ● Self-validating - No external tool to evaluate results ● Timely - written before code Source: http://agileinaflash.blogspot.co.il/2009/02/first.html
- 12. Tools of the trade ● Test Runner -> mocha.js ● Assertion Framework -> chai.js ● Stubbing/Mocking tools -> sinon.js
- 13. Testing Async Behavior ● Invoke the callback when your test is complete. ● By adding a callback (usually named done) to it(), Mocha will know that it should wait for this function to be called to complete the test. describe('Async behavior', function() { before(function(done) { somethingAsync(done) }) it('should do ok', () => {}) })
- 14. Exercise: Test different calls to ipify.org ● ipify.org - has 3 formats, regular, json and jsonp ● Write a unit test which tests each type ● I use “axios” = request library with promises const request = require('axios') function getMyIP(fmt) { fmt = typeof fmt == 'undefined' ? 'json' : fmt; return request.get(`https://api.ipify.org?format=${fmt}`) } gist
- 15. Why are these tests bad? ● They test someone else’s code ● They make I/O!
- 16. Sinon.js - stubbing, mocking, spying ● sinon.stub(obj, ‘method’).returns(1) What this does: ● Replaces obj.method() with function() { return 1 } ● Obj.method becomes a spy (gets special methods for inspection) ● Gets a .reset() method which rolls counters back ● Gets a .restore() method which restores everything back http://sinonjs.org/
- 17. Exercise: test our getMyIP’s different cases ● Stub axios.get ● Don’t forget to restore ● Test 3 cases: ○ No Input ○ JSON ○ JSONP ● Goals: ○ Test that Axios is called correctly ○ Don’t break the function’s signature
- 18. Bonus: pick your poison ● Testing Webservers ● Coverage reports with istanbul ● Syntactic sugar with sinon-as-promised, sinon-chai ● Integrating unit tests into CI/CD
- 19. Thank you @_rtam