fix outputFile for multiple source files

[gronke]

• introduces Unit-Tests using Mocha and Chai.expect
• fixes handling of multiple files writing to an outputFile

Description

When running on multiple source files reporting to a shared outputFile, only the output of the latest file was stored, because the file was deleted on each iteration.

tslint: {
    stdout: {
        options: {
            configuration: grunt.file.readJSON("tslint.json")
        },
        files: {
            src: ["*.ts"]
        }
    },
    file: {
        options: {
            configuration: grunt.file.readJSON("tslint.json"),
            outputFile: '/tmp/outputFile'
        },
        files: {
            src: ["*.ts"]
        }
    }
}

Expected Result:

• the errors written to tmp/outputFile are the same as printed to stdout

Fix

After the report of the first queued file was written, the appendToOutput option is set to true, so that the further output is appended to the file.

[gronke]

@adidahiya I'd like to cover more features with tests and would like to fork from this branch. Would be easier if the test setup s merged to master first, so that Pull-Request do not duplicate the changes.

[gronke]

@adidahiya this one looks ready to merge. #52 is implementing the same feature, but without the tests. What do you think?

[Cayan]

@gronke I'm sorry for any inconveniences, I didn't mean to be disrespectful or anything like it.
The first commit from #52 and this PR, both generate an invalid XML (CheckStyle or PMD formatter).
Which generates a bug. Those format types are used with a third party and with an invalid file something that would be working, poorly, but working would completely stop working at all.

Grunt-TSLint depends on TSLint, the solution for this problem needs be merged there first. There is one opened PR with it: palantir/tslint/pull/1472

Edit: #52 has been closed.

[gronke]

@Cayan no worries about anything please 😜 I'm using a fork of this plugin and lost sight of keeping the branch rebased. #52 was a nice reminder to rebase and clean up the pull-request, because obviously it's not only me waiting for the fix. My question from the previous comment should just make sure it's not the unit tests blocking this PR from being merged.

[jkillian]

Thanks for the PR @gronke, this looks good to me, I think it can be merged. Of course palantir/tslint#1472 will help remedy some more issues, but that doesn't hold this back