Add test coverage for moduleFilenameHelpers

[TheLarkInn]

After approving #16756, I realized we do not have coverage (that I could find) for this or other moduleFilenameHelper scenarios.

Documentation usages:
https://webpack.js.org/configuration/output/#outputdevtoolmodulefilenametemplate

Let's add a set of cases to cover this in tests.

[dhananjay0610]

Hi, @TheLarkInn can I start working on this, can you please assign this to me..

[alexander-akait]

You can send a PR

[webpack-bot]

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[webpack-bot]

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[ArchitGajjar]

Hi @TheLarkInn - is this issue still open ? can i work on this ?

[mayankkamboj47]

@TheLarkInn I've opened a PR. But I couldn't test some parts of the file, because the examples/test cases you guys left out in the comments actually don't match the output the functions give.

For replaceDuplicates, the comment says :

 const array = ["a", "b", "c", "a", "b", "a"];
 const result = ModuleFilenameHelpers.replaceDuplicates(array, (item, index, count) => `${item}-${count}`);
 // result: ["a-1", "b-1", "c", "a-2", "b-2", "a-3"]

But the actual output starts counting from 0, ["a-0", "b-0", "c-0", "a-1", "b-1", "a-2"]

For matchPart, the comment says

 ModuleFilenameHelpers.matchPart("foo.js", "foo."); // false

but the actual output is true.

Once you reply, I will first update the functions and then add tests for them. Let me know whether I should add the updates in a separate PR or the same one. Thanks ! I'm excited to make my first ever contribution that isn't just stylistic or a one-liner :))