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/** * Run this example with: * * If using the nested testing API, use the unstable flag as indicated in the command below * deno test --unstable ./testing/fast_check_example.ts */
import fc from "https://cdn.skypack.dev/fast-check";
function lowercaseString(text: string): string {  return text.toLowerCase();}
function add(a: number, b: number): number {  return a + b;}
function absoluteAddition(a: number, b: number): number {  return Math.abs(a) + Math.abs(b);}
// Using the Nested testing API from Deno 1.15Deno.test("can use fast check for property based testing", async (t) => {  await t.step("string after lower case should be of same length", async () => {    fc.assert(      fc.property(        fc.string(),        (text: string) => text.length === lowercaseString(text).length,      ),    );  });
  await t.step(    "absolute addition should always be greater or equal to regular addition",    async () => {      fc.assert(        fc.property(          fc.integer(-99, 99),          fc.integer(-99, 99),          (a: number, b: number) => add(a, b) <= absoluteAddition(a, b),        ),      );    },  );
  await t.step("string should contain itself", async () => {    fc.assert(fc.property(fc.string(), (text: string) => text.includes(text)));  });
  await t.step("string must contain substring", async () => {    fc.assert(      fc.property(        fc.string(),        fc.string(),        fc.string(),        (a: string, b: string, c: string) => (a + b + c).includes(b),      ),    );  });});