CODEWITHSUNDEEP
javascriptnode.jsunit-testing
Catfish
Catfish

Reputation: 19284

How can I test a method that logs to the console?

I want to test this method that logs (either to console.error, or a logger you pass in) properly. 

/**
 * Logs access errors in a way that is easy to quickly decipher the endpoint that was hit and the error that was received
 *
 * This was inspired from axios recommendation on handling errors https://www.npmjs.com/package/axios#handling-errors
 *
 * @param {Object | String} err      The error we want to log
 * @param {Object} [logger=console]  An optional logger which defaults to console
 * @public
 * @since 5.3.0
 */
function logAxiosErr(err, logger = console) {
  if (err.response) {
    const error = {
      error: `${err.response.status} - "${err.response.data}" with ${err.config.method.toUpperCase()} ${err.config.url}`,
      headers: err.config.headers,
      payload: err.config.data
    }
    // The request was made and the server responded with a status code that falls out of the range of 2xx
    logger.error(error)
  } else if (err.request) {
    // The request was made but no response was received
    // `error.request` is an instance of XMLHttpRequest in the browser and an instance of
    // http.ClientRequest in node.js
    logger.error(err.request)
  } else if (err.message) {
    // Something happened in setting up the request that triggered an Error
    logger.error(err.message)
  } else {
    logger.error(err)
  }

This test obviously doesn't test anything. How can I improve it to actually test that what was logged is what I'm expecting?

describe('#logAxiosError', () => {
    it('should log a string error ', () => {
      const err = 'SOME ERROR'
      expect(utils.logAxiosErr(err))
    })
})

Upvotes: 0

Views: 83

Answers (1)

Adi
Adi

Reputation: 727

One way to test dependency is to create a spy object (if using jasmine) for logger and pass it to logAxiosErr and then verify expectations on the spy object. So in your test above

describe('#logAxiosError', () => {
    it('should log a string error ', () => {
    const err = 'SOME ERROR'
    var logger = jasmine.createSpyObj('logger', ['error']);
    utils.logAxiosErr(err, logger);
    expect(logger.error).toHaveBeenCalledWith(err);
  })
})

Upvotes: 3

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