esbuild-plugin-run-node-test

Please write tests in your source file.
This esbuild plugin runs the tests and remove them from the bundle.

Installation

npm i -D esbuild esbuild-plugin-run-node-test

Usage Example

The following example uses Preact, but this plugin is framework-agnostic.

Source Code

• src/app.tsx

import { Fragment, h, render } from "preact";
import { add } from "./add";
import { mul } from "./mul";

const App = () => (
  <>
    <p>20 + 22 = {add(20, 22)}</p>
    <p>6 × 7 = {mul(6, 7)}</p>
  </>
);

render(<App />, document.body);

• src/add.ts

import assert from "node:assert/strict";
import test from "node:test";

export const add = (x: number, y: number) => x + y;

test("add(1, 2) should be 3", () => {
  assert.equal(add(1, 2), 3);
});

• src/mul.js

import assert from "node:assert/strict";
import test from "node:test";

export const mul = (x, y) => x * y;

test("mul(3, 2) should be 6", () => {
  assert.equal(mul(3, 2), 6);
});

Build Script

• build.mjs

import esbuild from "esbuild";
import runNodeTest from "esbuild-plugin-run-node-test";

esbuild.build({
  entryPoints: ["src/app.tsx"],
  outdir: "dist/",
  format: "esm",
  jsxFactory: "h",
  jsxFragment: "Fragment",
  bundle: true,
  plugins: [runNodeTest()],
});

Execution

$ node build.mjs

ok 1 - mul(3, 2) should be 6
  ---
  duration_ms: 0.000448975
  ...
ok 2 - add(1, 2) should be 3
  ---
  duration_ms: 0.00015755
  ...
1..2
# tests 2
# pass 2
# fail 0
# skipped 0
# todo 0
# duration_ms 0.133946737

$ cat dist/app.js

// node_modules/preact/dist/preact.module.js
/* ... */

// src/add.ts
var add = (x2, y2) => x2 + y2;

// src/mul.ts
var mul = (x2, y2) => x2 * y2;

// src/app.tsx
var App = () => /* @__PURE__ */ v(d, null, /* @__PURE__ */ v("div", null, "20 + 22 = ", add(20, 22)), /* @__PURE__ */ v("div", null, "6 \xD7 7 = ", mul(6, 7)));
S(/* @__PURE__ */ v(App, null), document.body);

Behavior

When bundling source files using esbuild with this plugin,

1. let testSourceCode = ""
2. each source file to be bundled is parsed using swc
   • if a source file includes import test from "node:test" and the imported test is called:
     • remove all test(...)
     • testSourceCode += `import "${the source file path}";`
   • remove the following import statements (by default):
     • "node:test"
     • "node:assert"
     • "node:assert/strict"
3. finally, when the bundling is complete, testSourceCode is also bundled using esbuild and run

Options

The options for this plugin and their default values are as follows:

runNodeTest({
  // narrow down the files to which this plugin should be applied.
  // https://esbuild.github.io/plugins/#filters
  filter: /\.[cm]?[jt]sx?$/,

  // if `false`, just remove import statements and `test(...)`, and tests are not run.
  run: true,

  // modules to be removed.
  removeImports: [
    // "node:test" is removed even if not specified.
    "node:assert",
    "node:assert/strict",
  ],

  // esbuild options used to bundle tests.
  // https://esbuild.github.io/api/
  testBuildOptions: {
    // define, external, loader, target, etc.
  },
});

Limitations

• Currently, the module format of the test bundle is CommonJS, not ES Module. This imposes some limitations (e.g., top-level await cannot be used).
• Currently, tests are not run in esbuild serve mode. Test code removal is fine.
  • Plugins' onEnd callback isn't triggerred in serve mode · Issue #1384 · evanw/esbuild
    https://github.com/evanw/esbuild/issues/1384
• Regardless of scope, function call statements whose names match the default import from "node:test" are removed.

  import foo from "node:test";
  
  {
    const foo = () => {};
    foo(); // will be removed
  }

With esbuild-plugin-pipe

If you use this plugin with esbuild-plugin-pipe, pass the same plugin instance to both esbuild-plugin-pipe and esbuild.

import esbuild from "esbuild";
import pipe from "esbuild-plugin-pipe";
import runNodeTest from "esbuild-plugin-run-node-test";

const runNodeTestInstance = runNodeTest({ filter: /^$/ });

esbuild.build({
  entryPoints: ["src/app.ts"],
  outdir: "dist/",
  bundle: true,
  minify: true,
  plugins: [
    pipe({
      filter: /\.[cm]?[jt]sx?$/,
      plugins: [runNodeTestInstance],
    }),
    runNodeTestInstance,
  ],
});

License

WTFPL