mock function from bun:test. 
test.tsimport { test, expect, mock } from "bun:test"; const random = mock(() => Math.random()); import { test, expect, mock } from "bun:test"; const random = mock((multiplier: number) => multiplier * Math.random()); mock() is a new function that’s been decorated with some additional properties. test.tsimport { mock } from "bun:test"; const random = mock((multiplier: number) => multiplier * Math.random()); random(2); random(10); random.mock.calls; // [[ 2 ], [ 10 ]] random.mock.results; // [ // { type: "return", value: 0.6533907460954099 }, // { type: "return", value: 0.6452713933037312 } // ] expect assertions about usage of the mock function, including how many times it was called, the arguments, and the return values. test.tsimport { test, expect, mock } from "bun:test"; const random = mock((multiplier: number) => multiplier * Math.random()); test("random", async () => { const a = random(1); const b = random(2); const c = random(3); expect(random).toHaveBeenCalled(); expect(random).toHaveBeenCalledTimes(3); expect(random.mock.args).toEqual([[1], [2], [3]]); expect(random.mock.results[0]).toEqual({ type: "return", value: a }); }); Was this page helpful?