How to get coverage on concatenated sources?

Thanks for the fantastic library; I had a question around getting coverage reports for build that use the grunt-concat plugin to concatenate several source files (or indeed, those projects that make use of browserify / require a pre-build step to generate valid JS).

I am using the following Gruntfile:

    grunt.initConfig({
        pkg: grunt.file.readJSON('package.json'),
        concat: {
            all: {
                src: ['src/js/**/*.js'],
                dest: 'dist/concatenated.js',
                options: {
                    banner: ";(function(root, undefined){\n'use strict';\n",
                    footer: "}(this));"
                }
            }
        },
        qunit: {
            options: {
                coverage: {
                    disposeCollector: true,
                    src: ['src/js/**/*.js'],
                    instrumentedFiles: 'temp/',
                    htmlReport: 'report/coverage',
                    coberturaReport: 'report/',
                    linesThresholdPct: 85
                }
            },
            all: ['test/unit/qunit-test-runner.html']
        }
    });

And my qunit-test-runner.html file has the following <head> to include the sources:

<!DOCTYPE html>
<html>
<head>
    <script src="lib/qunit-1.14.0.js"></script>
    <script src="../../dist/concatenated.js"></script>

    <script src="fileATests.js"></script>
    <script src="fileBTests.js"></script>
</head>
</html>

When I execute my build, I can see the QUnit assertions passing, however the coverage plugin does not pick up on my instrumented files, ie:

Running "concat:all" (concat) task
File dist/concatenated.js created.

Running "qunit:all" (qunit) task
Testing test/unit/qunit-test-runner.html ...................OK
>> 20 assertions passed (39ms)
>> Coverage:
>> -  Lines: 100%
>> -  Statements: 100%
>> -  Functions: 100%
>> -  Branches: 100%

If I modify my Gruntfile to point the coverage src at the concatenated output, I do get a valid coverage report, ie:

qunit: {
    options: {
        coverage: {
            ...
            src: ['dist/concatenated.js'],
            ...

However the HTML report now only shows a single file (concatenated.js) which is hard to consume / read, especially with a large project.

Is there a trick for mapping the coverage report back to the individual JS files, or do I actually need to make my QUnit Test Runner use the actual sources instead of the concatenated JS sources?

Thanks again Jonny.

asciidisco / grunt-qunit-istanbul

How to get coverage on concatenated sources? #28