CODEWITHSUNDEEP
node.jsjestjs
Kinfol
Kinfol

Reputation: 75

Test a console log function

  1. I have a function that prints a string

  2. I want to test that function actually prints the string provided

The way I understand this should work is: 1. store the log in a var 2. assert content stored in the var is toBe what I expect

const log = 'hello2';

let myFunction = (log) => {
    console.log(log);
    };
myFunction(log);

const {myFunction} = require('../function-conversion');

test('Function prints message: "hello"', () => {
    expect(myFunction(log).toBe(console.log("hello")))
});

Function prints message: "hello" (1ms)

Function prints message: "hello"

ReferenceError: log is not defined

at Object.log (tests/function-conversion.test.js:4:20)

console.log ../function-conversion.js:11 hello2

Upvotes: 1

Views: 3419

Answers (2)

Kinfol
Kinfol

Reputation: 75

I pumped up the initial function a bit. In case one should test a console.log message, he should push the string to an array.

let arrayOfMessages = [];
let functionThatPrintsTheArrayOfMessages = () => {
// pushing the messages to the array can be done when invoking the function as in line 19
//  console.log(message.push('hello','hi'));
    for (let i in arrayOfMessages){
    console.log(arrayOfMessages[i])
    };
    return arrayOfMessages;
};
functionThatPrintsTheArrayOfMessages(arrayOfMessages.push('hello', 'hi'));

This is the jest test.

test('Function prints message: "hello", "hi"', () => {
expect(functionThatPrintsTheArrayOfMessages()).toContain('hello')

expect(functionThatPrintsTheArrayOfMessages()).toContain('hi')

expect(functionThatPrintsTheArrayOfMessages()).toEqual(['hello', 'hi'])
});

I would like to know if this is correct and other ways of testing. Involving Jest.

Upvotes: 1

Hardik Shah
Hardik Shah

Reputation: 4200

There is an error to below line:

expect(myFunction(log).toBe(console.log("hello")))

While calling function myFunction(log) you should pass any string instead of log variable which is not declared anywhere (into function-conversion.test.js file) like "hello".

I don't have an environment up so couldn't test. But what you can do is:

describe('SearchResultsComponent', () => {
  let spy;
  
  let myFunction = (log) => {
    console.log(log);
  };
  myFunction(log);
  
  beforeAll(async () => {
    spy = jest.fn();
  });

  test('Function prints message: "hello"', () => {
    const log = 'hello';
    spy = jest.spyOn(console, 'log');
    myFunction(log);
    expect(spy).toHaveBeenCalled();
    expect(spy.calls.argsFor(0)).toEqual(['hello']);
  });
});

Upvotes: 1

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