1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
|
import {
pairOf,
positiveInt,
property,
shrinkPair,
shrinkPositive,
} from './property';
// from https://github.com/jlink/shrinking-challenge/blob/main/challenges/difference.md
const predicate1: (pair: [number, number]) => Promise<boolean> = ([x, y]) =>
Promise.resolve(x < 10 || x !== y);
describe('Find minimal counterexample', () => {
test('do not shrink example if no shrinker given', async () => {
const result = await property(pairOf(positiveInt), predicate1).then(p =>
p(42, 1),
);
expect(result.result).toBe('Falsified');
expect(result.counterexample).toBeNull;
});
test('shrink example if shrinker given', async () => {
const result = await property(
pairOf(positiveInt),
predicate1,
shrinkPair(shrinkPositive, shrinkPositive),
).then(p => p(42, 1));
expect(result.result).toBe('Falsified');
if (result.counterexample !== null) {
expect(result.counterexample.counterexample).toStrictEqual([10, 10]);
} else {
fail('no counterexample');
}
});
});
|
