Node's built-in assert API augmented with message formatting printf-style.
npm install assertf
var assert = require('assertf')
var apples = 2
var bananas = 3
// message vars are automatically positioned appropriately
assert.equal(apples, bananas, 'Oops, %d does not equal %d!')
// => AssertionError: Oops, 2 does not equal 3!
// you can also supply your own substitutions
assert.equal(apples, bananas, 'We have %d bananas, but only %d apples.',
bananas, apples)
// => AssertionError: We have 3 bananas, but only 2 apples.
MIT