Imported from jezek/funson (AGENTS.md). Install upstream with npx skills add jezek/funson. Copyright stays with the author.

Agent Guidelines

This project uses Go modules. When making changes:

• If you modify any Go files, format the changed code with gofmt -w.
• Run go test ./... only when Go code is updated and ensure it succeeds. Include the test output in the PR description.
• Keep commit messages concise.
• PR description should have a summary of changes and testing details.

Testing Conventions

• Tests should be table-driven. Declare a slice of test cases with a name field and execute each case using t.Run.
• Compare returned values and errors with reflect.DeepEqual as done in globalFunctions_test.go.
• When a function returns both a result and an error, store expected values in want and wantErr fields, mirroring TestPathFuncAndIsPathFunc.
• Use custom error types instead of fmt.Errorf when equality checks are required.
• Place tests in the *_test.go file that corresponds to the source file and keep them in the same order as the functions they verify.