backoff-web/tests/exponential_backoff_strategy.js

Fibonacci and exponential backoffs.

var ExponentialBackoffStrategy = require('../src/strategy/exponential');

exports['ExponentialBackoffStrategy'] = {

  'backoff delays should follow an exponential sequence': function (test) {
    var strategy = new ExponentialBackoffStrategy({
      initialDelay: 10,
      maxDelay: 1000
    });

    // Exponential sequence: x[i] = x[i-1] * 2.
    var expectedDelays = [10, 20, 40, 80, 160, 320, 640, 1000, 1000];
    var actualDelays = expectedDelays.map(function () {
      return strategy.next();
    });

    test.deepEqual(expectedDelays, actualDelays,
      'Generated delays should follow an exponential sequence.');
    test.done();
  },

  'backoff delay factor should be configurable': function (test) {
    var strategy = new ExponentialBackoffStrategy({
      initialDelay: 10,
      maxDelay: 270,
      factor: 3
    });

    // Exponential sequence: x[i] = x[i-1] * 3.
    var expectedDelays = [10, 30, 90, 270, 270];
    var actualDelays = expectedDelays.map(function () {
      return strategy.next();
    });

    test.deepEqual(expectedDelays, actualDelays,
      'Generated delays should follow a configurable exponential sequence.');
    test.done();
  },

  'backoff delays should restart from the initial delay after reset': function (test) {
    var strategy = new ExponentialBackoffStrategy({
      initialDelay: 10,
      maxDelay: 1000
    });

    strategy.next();
    strategy.reset();

    var backoffDelay = strategy.next();
    test.equals(backoffDelay, 10,
      'Strategy should return the initial delay after reset.');
    test.done();
  }
};