This function is used to change the behavior of an existing mock.
The following example creates a mock function using t.mock.fn(), calls the mock function, and then changes the mock implementation to a different function.
test('changes a mock behavior', (t) => {
let cnt = 0;
function addOne() {
cnt++;
return cnt;
}
function addTwo() {
cnt += 2;
return cnt;
}
const fn = t.mock.fn(addOne);
assert.strictEqual(fn(), 1);
fn.mock.mockImplementation(addTwo);
assert.strictEqual(fn(), 3);
assert.strictEqual(fn(), 5);
});