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const arb = miniFc.integer(0, 100);
abr.shrink(64) // potential output: 32, 16, 8, 4, 2, 1, 0

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type Generator<T> = {
    generate(mrng: Random): T;
    shrink(value: T): IterableIterator<T>;
}

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Property failed after 11 runs with value ["","w","vmethwd"] (seed: 42)

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miniFc.assert = (property, { seed = Date.now() } = {}) => {
    let rng = prand.xoroshiro128plus(seed);
    for (let runId = 0 ; runId !== 100 ; ++runId) {
        const valueUnderTest = property.generate(new Random(rng));
        if (!property.run(valueUnderTest)) {
            throw new Error(`Property failed after ${runId + 1} runs with value ${JSON.stringify(valueUnderTest)} (seed: ${seed})`);
        }
        rng = rng.jump();
    }
}

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miniFc.assert = property => {
    for (let runId = 0 ; runId !== 100 ; ++runId) {
        const seed = runId;
        const mrng = new Random(prand.xoroshiro128plus(seed));
        const valueUnderTest = property.generate(mrng);
        if (!property.run(valueUnderTest)) {
            throw new Error(`Property failed after ${runId + 1} runs with value ${JSON.stringify(valueUnderTest)}`);
        }
    }
}

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declare function assert<T>(property: Property<T>): void;

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const isSubstring = (pattern, text) => {
    return text.indexOf(pattern) > 0;
}

miniFc.assert(
    miniFc.property(
        miniFc.tuple(miniFc.string(), miniFc.string(), miniFc.string()),
        ([a, b, c]) => isSubstring(b, a + b + c)
    )
)

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miniFc.property = (generator, predicate) => {
    return {
        generate(mrng) {
            return generator.generate(mrng);
        },
        run(valueUnderTest) {
            return predicate(valueUnderTest);
        }
    }
}

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type Property<T> = {
    generate(mrng: Random): T;
    run(valueUnderTest: T): boolean;
}

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miniFc.string = () => map(
    miniFc.array(miniFc.character()),
    characters => characters.join('')
)

miniFc.dictionary = (valueGenerator) => map(
    miniFc.array(
        miniFc.tuple(
            miniFc.string(),
            valueGenerator