Fuzzing

Fuzzers live separately from specs, usually in assembly/__fuzz__/*.fuzz.ts.

Example:

import { expect, fuzz, FuzzSeed } from "as-test";

fuzz("bounded integer addition", (left: i32, right: i32): bool => {
  const sum = left + right;
  expect(sum - right).toBe(left);
  return sum >= i32.MIN_VALUE;
}).generate((seed: FuzzSeed, run: (left: i32, right: i32) => bool): void => {
  run(
    seed.i32({ min: -1000, max: 1000 }),
    seed.i32({ min: -1000, max: 1000 }),
  );
});

Commands:

bash

ast fuzz
ast fuzz math --runs 10000 --seed 42
ast test --fuzz
ast test --fuzz --fuzz-runs 10000 --fuzz-seed 42

Evaluation rules:

a thrown error or trap is a crash
a failed expect(...) is a failure
returning false is a failure
returning true or void passes if no assertion failed

Built-in seed helpers:

seed.boolean()
seed.i32({ min, max, exclude })
seed.u32({ min, max, exclude })
seed.f32({ min, max, exclude })
seed.f64({ min, max, exclude })
seed.bytes({ min, max, include, exclude })
seed.buffer({ min, max, include, exclude })
seed.string({ charset, min, max, include, exclude, prefix, suffix })
seed.array((seed) => value, { min, max })
seed.pick(values)

Supported string charsets:

ascii
alpha
alnum
digit
hex
base64
identifier
whitespace
custom

Notes:

fuzzers are registered separately from tests
ast test does not run fuzzers unless --fuzz is set
ast fuzz always builds fuzz targets as bindings
failures are reported in a fuzz summary, not in normal test counts
generator callback parameters currently need explicit type annotations in AssemblyScript

Related guides:

Fuzzing ​

Fuzzing