fix: ensure non-integers can be used as input to fuzzers

Author: holvonixAdvay

README.md

@@ -30,7 +30,7 @@ const target = t.union([t.string, t.type({ n: t.number, b: t.boolean })]);
 // Builds a particular fuzzer from the registry.
 const fuzzer = fuzz.exampleGenerator(r, target);
 
-// Make examples. The input integer and context
+// Make examples. The input number and context
 // fully determines the output example.
 for (const n of new Array(10).keys()) {
   console.log(JSON.stringify(fuzzer.encode([n, fuzz.fuzzContext()])));

src/core.ts

@@ -78,15 +78,15 @@ function gen<T, C extends t.Decoder<unknown, T> & BasicType>(
 }
 
 export function fuzzBoolean(_: FuzzContext, n: number): boolean {
-  return n % 2 === 0;
+  return rng(n).int32() % 2 === 0;
 }
 
 export function fuzzNumber(_: FuzzContext, n: number): number {
-  return n;
+  return n / Math.PI;
 }
 
 export function fuzzInt(_: FuzzContext, n: number): t.TypeOf<typeof t.Int> {
-  return Math.floor(n) as t.TypeOf<typeof t.Int>;
+  return rng(n).int32() as t.TypeOf<typeof t.Int>;
 }
 
 export function fuzzString(_: FuzzContext, n: number): string {

test/extra-fuzzers/test-io-ts-types.ts

@@ -10,6 +10,7 @@ import {
 import { isRight, Right } from 'fp-ts/lib/Either';
 import { date } from 'io-ts-types/lib/date';
 import { Encode } from 'io-ts';
+import { rngi } from '../../src/rng';
 
 const count = 100;
 
@@ -27,9 +28,9 @@ describe('extra-fuzzers', () => {
           r.register(...fz);
           p = exampleGenerator(r, b).encode;
         });
-        it(`generates decodable examples for inputs '[0, ${count})`, () => {
+        it(`generates decodable examples for seeds '[0, ${count})`, () => {
           for (const n of new Array(count).keys()) {
-            const v = p([n, fuzzContext()]);
+            const v = p([rngi(n) / Math.PI, fuzzContext()]);
             const d = b.decode(v);
             assert.ok(isRight(d), `must decode ${JSON.stringify(v)}`);
             assert.deepStrictEqual(
@@ -44,7 +45,7 @@ describe('extra-fuzzers', () => {
           .slow(500);
         it(`generates same examples 2nd time`, () => {
           for (const n of new Array(count).keys()) {
-            const v = p([n, fuzzContext()]);
+            const v = p([rngi(n) / Math.PI, fuzzContext()]);
             assert.deepStrictEqual(v, old[n]);
           }
         })

test/test-index.ts

@@ -5,6 +5,7 @@ import { exampleGenerator, fuzzContext } from '../src/';
 import { isRight, Right } from 'fp-ts/lib/Either';
 import { types } from './tested-types';
 import { Encode } from 'io-ts';
+import { rngi } from '../src/rng';
 
 const count = 100;
 
@@ -18,9 +19,9 @@ describe('io-ts-fuzzer', () => {
           const r = lib.createCoreRegistry()!;
           p = exampleGenerator(r, b).encode;
         });
-        it(`generates decodable examples for inputs '[0, ${count})`, () => {
+        it(`generates decodable examples for seeds '[0, ${count})`, () => {
           for (const n of new Array(count).keys()) {
-            const v = p([n, fuzzContext()]);
+            const v = p([rngi(n) / Math.PI, fuzzContext()]);
             const d = b.decode(v);
             assert.ok(isRight(d), `must decode ${JSON.stringify(v)}`);
             assert.deepStrictEqual(
@@ -35,7 +36,7 @@ describe('io-ts-fuzzer', () => {
           .slow(500);
         it(`generates same examples 2nd time`, () => {
           for (const n of new Array(count).keys()) {
-            const v = p([n, fuzzContext()]);
+            const v = p([rngi(n) / Math.PI, fuzzContext()]);
             assert.deepStrictEqual(v, old[n]);
           }
         })