Fuzzing

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

Basic shape:

import { expect, FuzzSeed, fuzz } 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 }),
  );
});

You can give one target its own operation count without changing the global fuzz.runs config:

fuzz("hot path stays stable", (): void => {
  expect(1 + 1).toBe(2);
}, 250);

Read Next

• Running Fuzzers
• Seed Generators
• Failure Reproduction

Core Rules

• failed expect(...) calls fail the current iteration
• returning false fails the current iteration
• returning true or void passes when no assertion failed
• traps, throws, and runtime failures are treated as crashes

ast test only runs fuzzers when you pass --fuzz.