issue_comments

https://github.com/PostHog/posthog/tree/master/cypress/integration has some useful examples, linked from this article: https://posthog.com/blog/cypress-end-to-end-tests

Also useful: their workflow https://github.com/PostHog/posthog/blob/master/.github/workflows/e2e.yml

Important to absorb the slightly bizarre assertion syntax from Chai - docs here https://www.chaijs.com/api/bdd/

I got Cypress working! I added the datasette.plugins code to the table template and ran a test called plugins.spec.js using the following: javascript context('datasette.plugins API', () => { beforeEach(() => { cy.visit('/fixtures/compound_three_primary_keys') }); it('should exist', () => { let datasette; cy.window().then(win => { datasette = win.datasette; }).then(() => { expect(datasette).to.exist; expect(datasette.plugins).to.exist; }); }); it('should register and execute plugins', () => { let datasette; cy.window().then(win => { datasette = win.datasette; }).then(() => { expect(datasette.plugins.call('numbers')).to.deep.equal([]); // Register a plugin datasette.plugins.register("numbers", (a, b) => a + b, ['a', 'b']); var result = datasette.plugins.call("numbers", {a: 1, b: 2}); expect(result).to.deep.equal([3]); // Second plugin datasette.plugins.register("numbers", (a, b) => a * b, ['a', 'b']); var result2 = datasette.plugins.call("numbers", {a: 1, b: 2}); expect(result2).to.deep.equal([3, 2]); }); }); });

Jest works with Puppeteer: https://jestjs.io/docs/en/puppeteer

I don't know if Jest on the command-line is the right tool for this. It works for the plugins.js script but I'm increasingly going to want to start adding tests for browser JavaScript features - like the https://github.com/simonw/datasette/blob/0.53/datasette/static/table.js script - which will need to run in a browser.

So maybe I should just find a browser testing solution and figure out how to run that under CI in GitHub Actions. Maybe https://www.cypress.io/ ?

Turned that into a TIL: https://til.simonwillison.net/javascript/jest-without-package-json

https://www.valentinog.com/blog/jest/ was useful.

I created a static/__tests__ folder and added this file as plugins.spec.js:

```javascript const datasette = require("../plugins.js");

describe("Datasette Plugins", () => { test("it should have datasette.plugins", () => { expect(!!datasette.plugins).toEqual(true); }); test("registering a plugin should work", () => { datasette.plugins.register("numbers", (a, b) => a + b, ["a", "b"]); var result = datasette.plugins.call("numbers", { a: 1, b: 2 }); expect(result).toEqual([3]); datasette.plugins.register("numbers", (a, b) => a * b, ["a", "b"]); var result2 = datasette.plugins.call("numbers", { a: 1, b: 2 }); expect(result2).toEqual([3, 2]); }); }); ```

In static/plugins.js I put this: ```javascript var datasette = datasette || {}; datasette.plugins = (() => { var registry = {}; return { register: (hook, fn, parameters) => { if (!registry[hook]) { registry[hook] = []; } registry[hook].push([fn, parameters]); }, call: (hook, args) => { args = args || {}; var results = []; (registry[hook] || []).forEach(([fn, parameters]) => { / Call with the correct arguments / var result = fn.apply(fn, parameters.map(parameter => args[parameter])); if (result !== undefined) { results.push(result); } }); return results; } }; })();

module.exports = datasette; `` Note themodule.exports` line at the end.

Then inside static/ I ran the following command:

``` % npx jest -c '{}' PASS tests/plugins.spec.js Datasette Plugins ✓ it should have datasette.plugins (3 ms) ✓ registering a plugin should work (1 ms)

Test Suites: 1 passed, 1 total Tests: 2 passed, 2 total Snapshots: 0 total Time: 1.163 s Ran all test suites. `` The-c {}was necessary because I didn't have a Jest configuration or apackage.json`.

https://jestjs.io/ looks worth trying here.