keep-silent

Keep console silent.

The output console.log may disturb normal testing log when you test some code which contains console output, keep-silent will help you to solve it.

Example usage:

const silent = require('keep-silent')
const assert = require('assert')

function output() {
  console.log('output some console logs for user')
  console.log('CATCH ME!')
}

silent(function (log) {
  output()

  assert(log.contains('CATCH ME'))
})

The silent function will capture console logs of it's callback, you can access caputred logs by param log.

Synopsis

Promise<String>|String silent(callback, options)

Arguments

callback

The callback can be a normal function or a generator function, you can return a Promise when your callback is async. Callback contains one parameter log, which has methods (see next section) for processing logs.

For async useage, we suggest use generator in slient callback just like co does:

slient(function * (log) {
  yield async1()
  assert(log.flush() === 'foo')

  yield async2()
  assert(log.flush() === 'bar')
})

options

• errorOutput: print output when error occurs (default: true)

Return

If callback is sync, the return value will be full captured logs String. If callback is async (return Promise or Generator function), the return value will be a Promise with full captured logs String.

The captured logs will NOT lose even if you have called log.clear() or log.flush().

Parameter log

The methods and props of callback parameter log:

log.clear()

Clear captured logs, the log.value will be a empty String.

log.contains(part[, strip])

• part, the part of log to check
• strip, strip cli ansi color chars (default: false)

Whether logs contain specified string, the part can be a String or RegExp object.

log.flush()

Clear captured logs and return it, the log.value will be a empty String.

log.value

Current captured logs.

Example

Keep some function slient:

const silent = require('keep-silent')

// keep silent (sync case)
let captured = silent(function () {
  outputSync('bla bla bla ....')
})

// keep silent (promise)
silent(function () {
  return outputPromise('do some async work ...')
}).then(function (captured) {
  // do what you like
})

// keep silent (generator)
silent(function * () {
  yield outputAsync('do some async work ...')
}).then(function (captured) {
  // do what you like
})

Capture logs for unit test (with mocha):

const assert = require('assert')
const silent = require('keep-silent')

function outputSync() {
  console.log('hello')
}

function outputAsync() {
  return new Promise(resolve => {
    setTimeout(_ => {
      console.log('world')
      resolve()
    }, 100)
  })
}

function dump() {
  console.log('just dump annoyed text .... HAHAHA LALALA')
}

describe('Testing for demo', function () {
  it('should output hello', function () {
    silent(function (log) {
      outputSync()
      assert(log.flush() === 'hello\n')

      dump()
      assert(log.contains('HAHAHA'))
    })
  })

  it('should output world', function () {
    return silent(function * (log) {
      yield outputAsync()
      assert(log.value === 'world\n')
    })
  })
})

License

MIT