ResultCollector tries to ensure that multiple references to the same file in a Test Plan only generate a single Writer.

However, it does not canonicalise the file names, so the same physical file may be written by two Writers.

For example, test.jtl and ./test.jtl will result in separate entries in the files HashMap. This could be fixed by using File.getCanonicalPath()

Also test.jtl and Test.jtl currently generate separate entries even on case-insensitive file systems. 

There does not seem to be a way to detect file system case-sensitivity in Java.

Path.toRealPath() produces unique names for case-insenstive systems but only works for existing files, so would require the file to be exist first. That might be acceptable here, because the purpose of the ResultCollector is to write the file. File.toCanonicalPath() does not take account of case sensitivity.

It looks as though File.getCanonicalPath() returns the file name with its actual case if the file exists.

Note that case-sensitivity is a property of the file system, not the OS, so the same host could potentially have multiple file systems with different case-sensitivity