Goblin

A mutation testing tool and library for Go, originally developed for the Software Verification and Validation course at UNIFESP and subsequently adapted to be used as a real-world library.

Goblin analyzes Go source code, generates syntactic mutations (modifying logical, arithmetic, relational operators, etc.), runs the test suite against each generated mutant, and reports which mutants survived — exposing gaps in the logical coverage of the existing tests.

Key Features:

• Parallel Execution: Support for concurrent execution using multiple workers to optimize test suite execution time.
• CI Integration: Option to enforce a minimum mutation score threshold (--threshold) to fail continuous integration builds.
• Flexible CLI & Library: Available both as a command-line tool (CLI) and an importable Go package.
• Reports: Generation of JSON reports for integration with external analysis tools.

Technical Challenges & Learnings:

• AST Manipulation: In-depth usage of Go’s native packages (go/ast, go/parser, go/printer, go/token) to parse, manipulate, and rebuild Go Abstract Syntax Trees (ASTs).
• Concurrency in Go: Orchestrated concurrent workers to manage multiple subprocesses of go test running mutations in parallel without mutual interference.
• API Design: Refactoring an academic codebase into a professionally packaged library, making it clean, documented, and reusable by the open-source community.