Advent of PBT 2021 - Day 16

Advent of PBT 2021 — Learn how to use property based testing and fast-check through examples

Our algorithm today is: reversed.
It comes with the following documentation and prototype:

/**
 * Produce a copy of the array but reversed
 * @param data - Reversed array
 */
declare function reversed<T>(data: T[]): T[];

We already wrote some examples based tests for it:

it("should be able to reverse the empty array", () => {
  expect(reversed([])).toEqual([]);
});
it("should be able to reverse an array with only one item", () => {
  expect(reversed([10])).toEqual([10]);
});
it("should be able to reverse an array with multiple items", () => {
  expect(reversed([10, 5, 2, 800])).toEqual([800, 2, 5, 10]);
});

How would you cover it with Property Based Tests?

In order to ease your task we provide you with an already setup CodeSandbox, with examples based tests already written and a possible implementation of the algorithm: https://codesandbox.io/s/advent-of-pbt-day-16-2uutt?file=/src/index.spec.ts&previewwindow=tests

You wanna see the solution? Here is the set of properties I came with to cover today's algorithm: https://dev.to/dubzzz/advent-of-pbt-2021-day-16-solution-3a4c

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Back to "Advent of PBT 2021" to see topics covered during the other days and their solutions.

More about this serie on @ndubien or with the hashtag #AdventOfPBT.