You should be able to write a simple fuzzer that hits your arguments to make sure your program is properly checking inputs. Actually, I would take this time to write a fuzzer to just learn how they are built.
Source: wiktionary
Fuzzer
Synonyms for "fuzzer"
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Sample sentences
3 total sentences available.
Found this bug on my own, no need for a fuzzer
Source: wiktionary
In exchange for this additional complexity it is more efficient in finding bugs than fuzzers that blindly generate inputs with rand.
Source: wiktionary