test-fuzz-gen

Generate _fuzz_test.go fuzz tests conforming to cryptoutil project standards.

Purpose

Use when creating fuzz tests for functions that parse or process external input. Fuzz tests go in a separate _fuzz_test.go file (ONLY fuzz functions). Use test-table-driven for deterministic example coverage and this skill for mutation-style input exploration.

Key Rules

• File suffix: _fuzz_test.go (ONLY fuzz functions, never mixed with unit tests)
• Minimum fuzz time: 15s per test
• CRITICAL: Function names MUST NOT be substrings of other fuzz function names — e.g. use FuzzHKDFAllVariants, NEVER FuzzHKDF if FuzzHKDFAllVariants exists in the same package
• Omit //go:build fuzz by default; only add a fuzz build tag when the package has fuzz-only helpers that must stay out of normal test builds
• Property tests that MUST NOT run during fuzzing: add //go:build !fuzz at top of _property_test.go file
• Corpus: provide seed entries covering edge cases (empty, nil, boundary values)
• Run from project root: go test -fuzz=FuzzXxx -fuzztime=15s ./path/to/pkg

Template

package mypkg_test

import (
"testing"
)

func FuzzParseInput(f *testing.F) {
// Seed corpus — cover edge cases
f.Add([]byte(""))
f.Add([]byte("valid-input"))
f.Add([]byte("{invalid json}"))
f.Add([]byte("\x00\xff"))

f.Fuzz(func(t *testing.T, data []byte) {
// Must not panic
result, _ := ParseInput(data)
if result != nil {
// Validate invariants
_ = result
}
})
}

References

Read ENG-HANDBOOK.md Section 10.7 Fuzz Testing Strategy for fuzz testing requirements — apply the 15s minimum fuzz time, _fuzz_test.go file suffix, unique function name rule, and seed corpus requirements from this section.

Read ENG-HANDBOOK.md Section 10.1 Testing Strategy Overview for test file type suffixes — ensure _fuzz_test.go files contain ONLY fuzz functions and cross-check that _property_test.go files use //go:build !fuzz if they must not run during fuzz corpus execution.