io-ts-fuzzer - Fuzzing for io-ts codecs and types

io-ts-fuzzer lets you generate examples of a given io-ts type.

Please note: API elements marked @experimental may be changed in breaking ways (including removal) without a major version release. Don't use such APIs if that's not acceptable for you.

Quick Start

After yarn add fp-ts io-ts io-ts-fuzzer...

import * as t from 'io-ts';
import * as fuzz from 'io-ts-fuzzer';

// Fuzzers for common types
const r = fuzz.createCoreRegistry();

// Type to fuzz
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 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()])));
}

See examples/quickstart/index.ts.

Types Supported

Currently supports (along with their closure under composition):

• t.array
• t.boolean
• t.exact
• t.Int
• t.intersection
• t.keyof
• t.literal
• t.null
• t.number
• t.partial
• t.readonly
• t.readonlyArray
• t.record
• t.recursive
• t.string
• t.tuple
• t.type (interface)
• t.undefined
• t.union
• t.unknown
• t.UnknownArray
• t.UnknownRecord
• t.void

If you yarn add monocle-ts io-ts-types and register the io-ts-types extra fuzzers via r.register(...await loadIoTsTypesFuzzers()), the following additional types will be supported:

• date
• BooleanFromString
• DateFromISOString
• DateFromNumber
• DateFromUnixTime
• IntFromString
• NonEmptyString
• NumberFromString
• UUID
• regexp

The following io-ts-types are composed of core types and you do not need to loadIoTsTypesFuzzers to fuzz them:

• either
• option

How To

Generate Conforming Examples and Verifying Decoder Behavior

Given a d = t.Decoder<I,A> (aka a t.Type), fuzz.exampleGenerator will build a t.Encoder<[number,FuzzContext],I> that will give example instances of I. The example instances should all pass on d.decode (which should return an identical example in the case of basic types). No exceptions should be thrown.

Configure Core Fuzzers

The FluentRegistry interface lets you easily configure certain core fuzzers, currently:

• maximum array length (array, readonlyArray, UnknownArray)
• extra properties inserted into partial and type (interface) objects
• type used to fuzz unknown types
• maximum record count (record, UnknownRecord)

Fuzz Recursive Types

When fuzzing recursive types, you can provide to the context a maxRecursionHint which specifies the requested maximum instantiations of any recursive type in a single path. Note that this is the maximum depth of recursive types, not all types. If the recursive depth has been reached, fuzzers that have a choice of which child(ren) to instantiate (like unions, partials, or arrays) will attempt to choose children that won't recurse.

Note this is only a hint -- sometimes the type definition won't allow the fuzzer to choose such a non-recursive path (and you'll get a stack limit error when attempting to generate the actual example from the generator).

Generate Variations of a Type

TODO

Piping Fuzzers

TODO

License

Read the LICENSE for details.
The entire NOTICE file serves as the NOTICE that must be included under Section 4d of the License.

# io-ts-fuzzer

This product contains software originally developed by Holvonix LLC.
Original Repository: https://github.com/holvonix-open/io-ts-fuzzer

Copyright (c) 2019 Holvonix LLC. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this software except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Dependencies may have their own licenses.