New tool RealDiff detects hidden runtime behavior changes in pull requests across six languages

RealDiff is an open-source tool that compares two Git revisions by actually running their tests, rather than just diffing source code, to catch behavior changes that ripple beyond the files a pull request touched. It builds a noise baseline from repeated base runs, then flags the first divergent behavior in each call tree, supporting analysis across six programming languages including .NET, Java, and Node.js. A demo shows a one-line change from an unstable to a stable sort algorithm silently altering the output of an unrelated pricing engine elsewhere in the codebase.