"You need to include some adapter that implements __karma__.start method" error after upgrading to 4.4.0

[dumbmatter]

Expected behaviour

Upgrading to 4.4.0 would not break my tests :)

Actual behaviour

When I run Karma, I get output like this:

$ yarn test-e2e
yarn run v1.19.1
$ karma start karma.conf.js
18 10 2019 00:21:11.344:INFO [preprocessor.rollup]: Generating bundle for ./src/deion/test/mocha.js
18 10 2019 00:21:11.601:INFO [karma-server]: Karma v4.3.0 server started at http://0.0.0.0:9876/
18 10 2019 00:21:11.601:INFO [launcher]: Launching browsers ChromeHeadless, FirefoxHeadless with concurrency unlimited
18 10 2019 00:21:11.608:INFO [launcher]: Starting browser ChromeHeadless
18 10 2019 00:21:11.640:INFO [launcher]: Starting browser FirefoxHeadless
18 10 2019 00:21:15.057:INFO [preprocessor.rollup]: Generating bundle for ./src/deion/test/smoke.js
18 10 2019 00:21:18.023:INFO [HeadlessChrome 77.0.3865 (Linux 0.0.0)]: Connected on socket --mqw4d12gSG7YxqAAAA with id 3778021
HeadlessChrome 77.0.3865 (Linux 0.0.0) ERROR
  You need to include some adapter that implements __karma__.start method!


18 10 2019 00:21:18.732:INFO [Firefox 69.0.0 (Ubuntu 0.0.0)]: Connected on socket wIsMYYYdCUttV51NAAAB with id 85435786
Firefox 69.0.0 (Ubuntu 0.0.0) ERROR
  You need to include some adapter that implements __karma__.start method!


error Command failed with exit code 1.

Environment Details

• Karma version (output of karma --version): 4.4.0
• Relevant part of your karma.config.js file

I'm not sure, so here's all of it:

// tools/karmaConfig.js

const alias = require("rollup-plugin-alias");
const build = require("./buildFuncs");
const rollupConfig = require("./rollupConfig");

const files = ["src/deion/test/mocha.js", "src/deion/test/smoke.js"];

const sport = build.getSport();

const rollupConfigTemp = rollupConfig("test");
rollupConfigTemp.plugins.unshift(
    alias({
        entries: [
            {
                find: "smoke-test-overrides",
                replacement: `./../../${sport}/worker/index.js`,
            },
        ],
    }),
);

module.exports = {
    frameworks: ["mocha", "source-map-support"],

    files: files.map(pattern => {
        return {
            pattern,
            watched: false,
        };
    }),

    preprocessors: {
        "src/**/*.js": ["rollup"],
    },

    // http://stackoverflow.com/a/42379383/786644
    browserConsoleLogOptions: {
        terminal: true,
        level: "",
    },

    autoWatch: false,

    singleRun: true,

    rollupPreprocessor: {
        ...rollupConfigTemp,
        output: {
            format: "iife",
            indent: false,
            name: "bbgm",
            sourcemap: true,
        },
    },

    browserNoActivityTimeout: 15 * 60 * 1000, // 15 minutes
    browserDisconnectTimeout: 15 * 60 * 1000, // 15 minutes

    browsers: ["ChromeHeadless", "FirefoxHeadless"],
};

// karma.conf.js

const karmaConfig = require("./tools/karmaConfig");

module.exports = function(config) {
    config.set({
        ...karmaConfig,
        autoWatch: false,
        singleRun: true,
        browsers: ["ChromeHeadless", "FirefoxHeadless"],
    });
};

Steps to reproduce the behaviour

1. Clone this repo https://github.com/dumbmatter/gm-games/
2. Upgrade Karma from 4.3.0 to 4.4.0
3. Run yarn install && yarn test-e2e

Additional info

I bisected the commits between v4.3.0 and v4.4.0 and found that this issue was introduced in commit 3ffcd83. I haven't looked into it any further than that.

[johnjbarton]

Please retry without 'source-map-support' and then without 'rollup'. Maybe related to #3383

[johnjbarton]

Please try 4.4.1

[dumbmatter]

That fixed it, thanks!