Test your vim with js

A harness for testing vim via javascript. Provides an ergonimic interface to a NeovimClient for easy testing of vim (plugins or the like).

How to install it

Install nvim-test-js along with your chosen test runner (I'm using yarn, and am choosing mocha to run my tests with)

yarn init
yarn add nvim-test-js mocha

Then add the test script name to your package.json and run with yarn test

"scripts": {
  "test": "mocha --exit test/**/*.test.js",
}

Typescript?

I find it easier to explore unknown apis (like Neovim's) with typescript. If you have the same preference you can do the above but with typescript:

yarn init
yarn add nvim-test-js mocha @types/mocha @types/node ts-node typescript

Then your test script in your package.json would become:

"scripts": {
  "test": "mocha --require ts-node/register --exit test/**/*.test.ts",
}

How to use it

Use the entrypoint withVim to encapsulate your test with a live headless vim instance. You can then exercise vim to your liking via the NeovimClient api. Depending on whether you're running typescript or vanilla js - you can execute the files below with yarn test

// test/index.test.js

const assert = require("assert");
const { withVim } = require("nvim-test-js");

it("gives me the vim", () =>
  withVim(async nvim => {
    const result = await nvim.commandOutput('echo "It works!"');
    assert.equal(result, "It works!");
  }));

// test/index.test.ts

import assert from "assert";
import withVim from "nvim-test-js";

it("gives me the vim", () =>
  withVim(async nvim => {
    const result = await nvim.commandOutput('echo "It works!"');
    assert.equal(result, "It works!");
  }));

A few helpers

Commonly when testing plugins I find I need to setup the buffer with the cursor in a particular location. A helper method for this is available as setBuffer where the cursor is represented by |.

import assert from "assert";
import withVim, {getBuffer, setBuffer} from "nvim-test-js";

it("poulates a buffer with a cursor position", () =>
  withVim(async nvim => {
    await setBuffer(nvim, "f|oo")

    assert.deepEqual(await getBuffer(nvim), "foo")
    assert.deepEqual(await nvim.call("getpos", "."), [0, 1, 2, 0])
  }));

it("can do the same with an array of lines", () =>
  withVim(async nvim => {
    await setBuffer(nvim, ["foo", "b|ar"])

    assert.equal(await getBuffer(nvim), "foo\nbar")
    assert.deepEqual(await nvim.call("getpos", "."), [0, 2, 2, 0])
  }));

Why?

I do enjoy playing with vim projects - but after all that work I find myself fatigued when testing it with vim related frameworks annd concepts. Give me some good ol' mocha, or jest or whatever and I'm happier. I find the javascript testing universe much more joyful - maybe you will too.