gremlins-ts/src/strategies/bySpecies.ts

A monkey testing library written in JavaScript, for Node.js and the browser. Use it to check the robustness of web applications by unleashing a horde of undisciplined gremlins.

import { executeInSeries, configurable } from "../utils";

/**
 * For each species, execute the gremlin 200 times, separated by a 10ms delay
 *
 *   var bySpeciesStrategy = gremlins.strategies.bySpecies();
 *   horde.strategy(bySpeciesStrategy);
 *
 * The actual attack duration depends on the number of species in the horde.
 *
 * The bySpecies strategy can be customized as follows:
 *
 *   bySpeciesStrategy.delay(10); // delay in milliseconds between each gremlin action
 *   bySpeciesStrategy.nb(200);   // number times to execute each gremlin
 *
 * Example usage:
 *
 *   horde
 *     .gremlin(gremlins.species.clicker())
 *     .gremlin(gremlins.species.formFiller())
 *     .strategy(gremlins.strategies.bySpecies()
 *       .delay(1000) // one action per second
 *       .nb(10)      // each gremlin will act 10 times
 *     )
 *     .unleash();
 *
 *   // t     clickerGremlin clicked
 *   // t+1s  clickerGremlin clicked
 *   // ...
 *   // t+9s  clickerGremlin clicked
 *   // t+10s formFillerGremlin filled
 *   // t+11s formFillerGremlin filled
 *   // ...
 *   // t+19s formFillerGremlin filled
 *   // t+20s, end of the attack
 */

type Callback = () => void;
type Params = {
  nb: number;
};
type Config = {
  delay: number;
  nb: number;
};

export function bySpecies() {
  const config: Config = {
    delay: 10, // delay in milliseconds between each attack
    nb: 200 // number of attacks to execute (can be overridden in params)
  };

  let stopped: boolean;
  let doneCallback: Callback | null | undefined = null;

  function bySpeciesStrategy(
    gremlins: Array<() => void>,
    params: Params,
    done?: Callback
  ) {
    const nb = params && params.nb ? params.nb : config.nb;
    const gremlinsCopy = [...gremlins];
    // @ts-ignore
    const horde = this;

    stopped = false;
    doneCallback = done; // done can also be called by stop()

    function executeNext(
      gremlin: undefined | (() => void),
      i: number,
      callback: Callback
    ) {
      if (!gremlin || stopped) {
        return;
      }
      if (i >= nb) {
        return callback();
      }

      executeInSeries([gremlin], [], horde, () => {
        setTimeout(function() {
          executeNext(gremlin, ++i, callback);
        }, config.delay);
      });
    }

    function executeNextGremlin() {
      if (stopped) return;
      if (gremlinsCopy.length === 0) {
        return callDone();
      }
      executeNext(gremlinsCopy.shift(), 0, executeNextGremlin);
    }

    executeNextGremlin();
  }

  bySpeciesStrategy.stop = () => {
    stopped = true;
    setTimeout(callDone, 4);
  };

  function callDone() {
    if (typeof doneCallback === "function") {
      doneCallback();
    }
    doneCallback = null;
  }

  configurable(bySpeciesStrategy, config);

  return bySpeciesStrategy;
}