Jest-Bench

Run benchmark with Jest, write benchmark files along your test files and benchmark using any existing test environment you're using. This package rely on the excellent benchmark package to function.

Which version to install

Some environments such as jest-electron are only useable with Jest version 27, therefore this package take its version after jest version for easy installation:

Jest version	Jest-Bench version
26.x.x	26.x.x
27.x.x	27.x.x

For contributors, branch main works with Jest version 27, while branch v26 works with Jest version 26.

How to use

Install

npm i -D jest-bench

Create a jest config file just for running benchmarks. You can use name such as jest-bench.config.json.

{
  // Jest-bench need its own test environemtn to function
  "testEnvironment": "jest-bench/environment",
  "testEnvironmentOptions": {
    // still Jest-bench environment will run your environment if you specify it here
    "testEnvironment": "jest-environment-jsdom",
    "testEnvironmentOptions": {
      // specify any option for your environment
    }
  },
  // always include "default" reporter along with Jest-bench reporter
  // for error reporting
  "reporters": ["default", "jest-bench/reporter"],
  // will pick up "*.bench.js" files or files in "__benchmarks__" folder.
  "testRegex": "(/__benchmarks__/.*|\\.bench)\\.(ts|tsx|js)quot;,
  ...
}

To see more examples, look at jest-*.config.ts files. You can now write your benchmark files with name *.bench.js or save them in __benchmarks__ folder.

import { benchmarkSuite } from "jest-bench";

let a;

benchmarkSuite("sample", {
  // setup will not run just once, it will run for each loop
  setup() {
    a = [...Array(10e6).keys()];
  },

  // same thing with teardown
  teardown() {
    if (a.length < 10e6) a.unshift(0);
  },

  ["Array.indexOf"]: () => {
    a.indexOf(555599);
  },

  ["delete Array[i]"]: () => {
    expect(a.length).toEqual(10e6);
    delete a[0];
  },

  ["Array.unshift"]: () => {
    a.unshift(-1);
  },

  ["Array.push"]: () => {
    a.push(1000000);
  },
});

To see more examples, check out test folder. You can now run benchmarks like this:

npx jest --projects jest-bench.config.json

Benchmark results are output to benchmarks/result.txt in addition to being print so you might want to add that to .gitignore.

# .gitignore
benchmarks/result.txt

Reference

benchmarkSuite(name, description[, timeout])

Create and run a new suite. Each suite create and is associated with a describe block underneath.

• name: string, name of suite.
• description: object, an object with each key represent a single benchmark. Behind the scene each benchmark run in a test block therefore you can also write jest assertion, even though it makes little sense to do so as it will affect benchmark result. Special keys include:
  • setup: run before each loop of benchmark. Note that this along with teardown are evaled together with the benchmark so once you declare this, any variable defined outside of setup and teardown become invisible to the benchmark. If this and teardown are not defined then benchmarks will still be able to see variables in outer scopes.
  • teardown: run after each loop of benchmark. Note the caveat above.
  • setupSuite: run once before all benchmarks. This in effect is the same as a beforeAll block (and it does call beforeAll underneath). Again you probably don't want to define or initialize variables here if you also include setup or teardown.
  • teardownSuite: run once after all benchmarks have concluded.
• timeout: number of milliseconds before a benchmark timeout. Default to 60000.