Difference Between Clearing, Resetting, and Restoring Mocks
October 26, 2024
Clearing
.mockClear() clears the recorded calls to the mock functions.
const fn = vi.fn()
fn('one')
expect(fn).toHaveBeenCalledTimes(1) // ✅
// Makes the mock function forget about
// any calls that happened before this point.
fn.mockClear()
fn('two')
expect(fn).toHaveBeenCalledTimes(1) // ✅
Resetting
.mockReset() clears the recorded calls and removes any mock implementation.
// Let's spy on console!
// Calling `vi.spyOn` wraps the global `console.log` function
// in a mock function. Let's also provide a mock implementation
// so console calls in test don't actually print anything.
const spy = vi.spyOn(console, 'log').mockImplementation(() => {})
console.log('you will not see this') // nothing is printed!
expect(console.log).toHaveBeenCalledTimes(1) // ✅
// Makes the mock forget about any calls to it
// and also removes any mock implementation it may have.
spy.mockReset()
console.log('you will see this!') // prints "you will see this"
expect(console.log).toHaveBeenCalledTimes(1) // ✅
Restoring
.mockRestore() removes the mock, undoing it altogether.
const spy = vi.spyOn(console, 'log')
console.log(1)
expect(console.log).toHaveBeenCalledTimes(1) // ✅
// Revert this mock, restoring the original implementation
// of the spied function (console.log).
spy.mockRestore()
expect(console.log).toHaveBeenCalledTimes(0)
// ❌ TypeError: [Function log] is not a spy or a call to a spy!