This blog post explains how Trail of Bits developed a fuzzing harness for Fuel Labs and used it to identify opcodes that charge too little gas in the Fuel VM, the platform on which Fuel smart contracts run. The LibAFL-based fuzzer is implemented as a Rust binary with subcommands for generating seeds, executing test cases in isolation, collecting gas usage statistics of test cases, and actually executing the fuzzer. Figure 4: Python script to determine gas usage vs execution time of the discovered test inputs