test-module-is-runnable.js

const puppeteer = require("puppeteer");

const http = require("http");
const fs = require("fs");
const port = 3876;

const scriptContent = `
import sinon from '/sinon-esm.js';

console.log('sinon is here', typeof sinon);
console.log('the answer of all is', sinon.stub().returns(42)());
window.sinonLoaded = true;
window.mySinon = sinon;
`;

const htmlWithModuleScript = "";
//const htmlWithModuleScript = `
//<script type="module">
//${content}
//</script>
//`;

// change to where our built sinon module resides
process.chdir(`${__dirname}/../../pkg/`);
const sinonModule = fs.readFileSync("./sinon-esm.js");

// This runs in the browser (Chrome)!
async function evaluatePageContent() {
    console.log("Starting browser ...");

    const browser = await puppeteer.launch();
    const page = await browser.newPage();
    await page.goto("http://localhost:3876");

    page.on("error", function(err) {
        const theTempValue = err.toString();
        console.log("Error: " + theTempValue);
    });

    const frame = page.mainFrame();
    await frame.addScriptTag({ content: scriptContent, type: "module" });

    page
        .waitForFunction(() => typeof window.sinonLoaded !== "undefined", {
            timeout: 5000
        })
        .then(() => browser.close())
        .then(() => {
            console.log("We were successful");
            process.exit();
        })
        .catch(err => {
            console.log("Failed: ", err);
        })
        .then(() => browser.close())
        .then(() => process.exit(1));
}

const app = http.createServer((req, res) => {
    res.writeHead(200);

    if (req.url.match(/sinon-esm\.js/)) {
        console.log("server responded with sinon module");
        res.end(sinonModule);
    } else {
        res.end(htmlWithModuleScript);
    }
});

app.listen(port, evaluatePageContent);
//app.listen(port);

This times out, for some reason. Chrome and Firefox finds the sinonLoaded without problems.