Coverage artifacts in js code when stringifying a function at runtime.

[bsommardahl]

I learned about how Istanbul measures coverage in a really cool way thanks to my current problem. My current task is to write a javascript function and then return the function as a string. My unit test attempts to eval the string function and fails because of the following error:

ReferenceError: __cov_HnbYpbOoQM4MaLYAY_l6Ig is not defined

When I take a look at the value of my function string, I see this:

function (browser,tabTitle){
    __cov_HnbYpbOoQM4MaLYAY_l6Ig.f['3']++;
    __cov_HnbYpbOoQM4MaLYAY_l6Ig.s['10']++;
    var currentTabId=browser.getCurrentTabId();
    __cov_HnbYpbOoQM4MaLYAY_l6Ig.s['11']++;
    browser.getTabIds().forEach(id=>{
        __cov_HnbYpbOoQM4MaLYAY_l6Ig.s['12']++;
        browser.switchTab(id);
        __cov_HnbYpbOoQM4MaLYAY_l6Ig.s['13']++;
        if(browser.getTitle().indexOf(tabTitle)>-1){
            __cov_HnbYpbOoQM4MaLYAY_l6Ig.b['2'][0]++;
            __cov_HnbYpbOoQM4MaLYAY_l6Ig.s['14']++;
            return false;
        }
        else {
            __cov_HnbYpbOoQM4MaLYAY_l6Ig.b['2'][1]++;
            __cov_HnbYpbOoQM4MaLYAY_l6Ig.s['15']++;
            browser.switchTab(currentTabId);
        }
    });
}

Cool huh? Now I understand how instanbul is able to see what code was visited during unit test execution. In the coverage context, I'm sure __cov_HnbYpbOoQM4MaLYAY_l6Ig is defined and works fine. But, in my unit test context, it doesn't exist. :)

Here are a couple of gulp tasks that I think are relevant:

gulp.task('pre-test', function () {
  return gulp.src(['build/**/*.js', '!build/src/features/**/*'])
    .pipe(istanbul({includeUntested: true}))
    .pipe(istanbul.hookRequire());
});

gulp.task('unit-tests',** ['clean-coverage', 'pre-test'], function(){
    return gulp.src(['build/src/**/*.spec.js'])
        .pipe(mocha({reporter: 'spec'}))
        .pipe(istanbul.writeReports({
            dir: './coverage',
            reportOpts: {
                dir: './coverage'
            },
            reporters: ['text-summary', 'html']
        }))
        .pipe(istanbul.enforceThresholds({ thresholds: { global: 80 } }));
});

So, I think I need a way to prevent istanbul from adding coverage code to this function. I have tried /* istanbul ignore next */ in various places with no luck (coverage code still present). I would gladly provide my unit test context with a defined __cov_HnbYpbOoQM4MaLYAY_l6Ig but that slug changes each time.

Not sure what to try next. Any help would be appreciated!

[tagyoureit]

This (#310) helped me resolve the issue at runtime. Maybe it will help you with Gulp tasks, too?