class MockFunctionContext

A getter that returns a copy of the internal array used to track calls to the mock. Each entry in the array is an object with the following properties.

This function returns the number of times that this mock has been invoked. This function is more efficient than checking ctx.calls.length because ctx.calls is a getter that creates a copy of the internal call tracking array.

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);
});

This function is used to change the behavior of an existing mock for a single invocation. Once invocation onCall has occurred, the mock will revert to whatever behavior it would have used had mockImplementationOnce() not been called.

The following example creates a mock function using t.mock.fn(), calls the mock function, changes the mock implementation to a different function for the next invocation, and then resumes its previous behavior.

test('changes a mock behavior once', (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.mockImplementationOnce(addTwo);
  assert.strictEqual(fn(), 3);
  assert.strictEqual(fn(), 4);
});

Resets the call history of the mock function.

Resets the implementation of the mock function to its original behavior. The mock can still be used after calling this function.