propcheck 0.1.6

A library for exhaustive and randomized testing of Dart properties.

Exhaustive and Randomized Testing of Properties

A library for exhaustive and randomized testing of Dart properties, based on enumerators. It is inspired by Haskell's smallcheck and quickcheck. If you don't know these libraries, have a look at the small demo below to get an idea of what it can be useful for. I also wrote a post that goes into more details.

Quick Start

import 'dart:collection';
import 'package:propcheck/propcheck.dart';
import 'package:enumerators/combinators.dart' as c;
import 'package:unittest/unittest.dart';

// defines append and reverse
part 'demolib.dart';

/* --- the properties to test --- */

// this should always hold
bool good(List xs, List ys) =>
    Arrays.areEqual(reverse(append(xs, ys)),
                    append(reverse(ys), reverse(xs)));

// this should NOT always hold
bool bad(List xs, List ys) =>
    Arrays.areEqual(reverse(append(xs, ys)),
                    append(reverse(xs), reverse(ys)));

/* --- how we test them --- */

main() {
  // we define an enumeration of lists of integers
  final boolsLists = c.listsOf(c.bools);

  // 'good' and 'bad' take 2 arguments each so we use forall2
  Property goodProperty = forall2(boolsLists, boolsLists, good);
  Property badProperty = forall2(boolsLists, boolsLists, bad);

  // we test the properties against *every* pair of lists of bools whose
  // combined size is <= 10.
  group('smallcheck', () {
    final sc = new SmallCheck(depth: 10);
    test('good', () => sc.check(goodProperty));
    test('bad', () => sc.check(badProperty));
  });

  // we test the properties against random pairs of lists of bools of
  // combined size 0, 1, ..., 300.
  group('quickcheck', () {
    final qc = new QuickCheck(maxSize: 300, seed: 42);
    test('good', () => qc.check(goodProperty));
    test('bad', () => qc.check(badProperty));
  });
}

Output:

unittest-suite-wait-for-done
PASS: smallcheck good
FAIL: smallcheck bad
  Caught falsified after 11 tests
    argument 1: [true]
    argument 2: [false]
  
  [...]
  
PASS: quickcheck good
FAIL: quickcheck bad
  Caught falsified after 5 tests
    argument 1: [false]
    argument 2: [false, false, true]
  
  [...]

2 PASSED, 2 FAILED, 0 ERRORS

Try it!

git clone https://code.google.com/p/dart-check/
cd dart-check
pub install
dart example/demo.dart

Enjoy the progress indicator, probably the most elaborate part of this library :)