ERROR [preprocessor.coverage]: Unexpected token

I am trying to add coverage to my project, I keep getting this error every time I run `npm run karma`


snippet of `algorithms.js`

```
/**
Currently used only for adding 'assert' class to algorithm lists
*/

import css from "text!../../assets/algorithms.css";

export const name = "core/algorithms";

export async function run() {
const elements = Array.from(document.querySelectorAll("ol.algorithm li"));
elements
.filter(li => li.innerText.trim().startsWith("Assert: "))
.forEach(li => li.classList.add("assert"));
if (document.querySelector(".assert")) {
const style = document.createElement("style");
style.textContent = css;
document.head.appendChild(style);
}
}
```

`karma.conf.js`

```
// Karma configuration
// Generated on Fri Feb 26 2016 13:09:51 GMT+1100 (AEDT)
/*globals module, require, process*/
"use strict";
module.exports = function(config) {
const options = {
// base path that will be used to resolve all patterns (eg. files, exclude)
basePath: "./",

// frameworks to use
// available frameworks: https://npmjs.org/browse/keyword/karma-adapter
frameworks: ["jasmine", "requirejs", "detectBrowsers"],

// configuration
detectBrowsers: {
enabled: !config.browsers.length,
usePhantomJS: false,
postDetection(browsers) {
return (
browsers
// Remove IE
.filter(browser => browser !== "IE")
);
},
},

// list of files / patterns to load in the browser
files: [
"js/deps/jquery.js",
{
pattern: "assets/**/*.*",
included: false,
served: true,
},
{
pattern: "tests/support-files/**/*",
included: false,
served: true,
},
{
pattern: "builds/**/*.*",
included: false,
served: true,
},
{
pattern: "js/deps/marked.js",
included: false,
served: true,
},
{
pattern: "js/**/*.*",
included: false,
served: true,
},
{
pattern: "tests/**/*-spec.js",
included: false,
served: true,
},
{
pattern: "tests/data/**/*",
included: false,
served: true,
},
{
pattern: "tests/*.html",
included: false,
served: true,
},
{
pattern: "tests/**/*.html",
included: false,
served: true,
},
{
pattern: "worker/*.js",
included: false,
served: true,
},
{
pattern: "src/**/*.js",
included: false,
},
"tests/spec/SpecHelper.js",
"tests/test-main.js",
],

// list of files to exclude
exclude: ["**/*.swp", "*.swp", ".DS_Store"],

proxies: {
"/about-blank.html": "/base/tests/about-blank.html",
"/assets/": "/base/assets/",
"/js/": "/base/js/",
"/builds/": "/base/builds/",
"/tests/": "/base/tests/",
"/spec/": "/base/tests/spec/",
"/deps/": "/base/js/deps/",
"/js/deps/": "/base/js/deps/",
"/base/deps/": "/base/js/deps/",
"/worker/respec-worker.js": "/base/worker/respec-worker.js",
"/support-files/hljs-testlang.js":
"/base/tests/support-files/hljs-testlang.js",
},

// preprocess matching files before serving them to the browser
// available preprocessors: https://npmjs.org/browse/keyword/karma-preprocessor
preprocessors: {
// source files, that you wanna generate coverage for
// do not include tests or libraries
// (these files will be instrumented by Istanbul)
"src/**/*.js": ["coverage"],
},

// test results reporter to use
// possible values: "dots", "progress"
// available reporters: https://npmjs.org/browse/keyword/karma-reporter
reporters: ["mocha", "progress", "coverage", "coveralls"],

// web server port
port: config.port || 9876,

// enable / disable colors in the output (reporters and logs)
colors: true,

// level of logging
// possible values: config.LOG_DISABLE || config.LOG_ERROR || config.LOG_WARN || config.LOG_INFO || config.LOG_DEBUG
logLevel: config.LOG_INFO,

// enable / disable watching file and executing tests whenever any file changes
autoWatch: true,

// See "detectBrowsers"
//browsers: ["Chrome", "Safari", "Firefox"],

// Continuous Integration mode
// if true, Karma captures browsers, runs the tests and exits
singleRun: false,

// Concurrency level
// how many browser should be started simultaneous
concurrency: 1,

browserNoActivityTimeout: 100000,

client: {
args: ["--grep", config.grep || ""],
},

coverageReporter: {
includeAllSources: true,
type: "lcov", // lcov or lcovonly are required for generating lcov.info files needed for coveralls.
dir: "coverage/",
},
};
if (process.env.TRAVIS) {
process.env.CHROME_BIN = require("puppeteer").executablePath();
options.detectBrowsers.enabled = false;
options.autoWatch = false;
options.singleRun = true;
options.concurrency = 1;
options.reporters = ["mocha", "progress", "coverage", "coveralls"];
options.browsers = ["ChromeHeadless"];
}
config.set(options);
};
```

Reproduce the failure with `npm run karma`, then start with `karma.conf.js` and its `src/**/*.js` coverage preprocessor. Compare the reported unexpected token with the syntax in `algorithms.js` and the configured test entry points. Done means the Karma run completes without the preprocessor error and coverage is generated.

Written by the indexing model from the issue text.