Regex to match only some filenames

Using std::regex and given a file path, I want to match only the filenames that end with .txt and that are not of the form _test.txt or .txtTEMP.

So, for example:

• somepath/testFile.txt should match.
• somepath/testFile_test.txt should not match.
• somepath/testFile.txtTEMP should not match.

What is the correct regex for such a pattern?

What I have tried:

(.*?)(\.txt) ---> This matches any file path ending with .txt.

To exclude files that contains _test I tried to use negative lookahed:

(.*?)(?!_test)(\.txt)

But it didn't work.

I also tried negative lookbehind but MSVC14 (Visual Studio 2015) throws a std::regex_error exception when creating the regex, so I'm not sure if it's not supported or I'm using the wrong syntax.