The 1.0 version of NSRegexTester for Mac was available to download on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The NSRegexTester installer is commonly called nsregextester.zip.
This free Mac app was originally designed by Aaron Vegh. We recommend checking the downloaded files with any free antivirus. The software lies within Productivity Tools, more precisely Office Tools. The most popular version of the application is 1.0. This free software can be installed on Mac OS X 10.8 or later.
From the developer:
NSRegexTester is a very simple Mac OS X open source application that allows you to test regular expressions against sample text. It is based on the Mac OS SDK's implementation of NSRegularExpression, which is based on ICU. This tool ensures that the expressions you enter will actually work when implemented in code.
You may want to check out more Mac applications, such as PitStop Extreme, FileOpenInstaller or Blurb Tally, which might be similar to NSRegexTester.