jest - how to avoid using a spy for a getter

Question

I have this

jest.spyOn(store.customerData, "isValid", "get").mockReturnValue(true);

that I'd like to refactor to use a typical jest.fn() mock like this:

store.customerData.isValid = jest.fn().mockResolvedValue(true)

but I get an error claiming that the property is read only.

Can you add the minimal code which you want to test and the error detail? — Lin Du, Nov 12 '19 at 01:49

score 0 · Accepted Answer · answered Nov 12 '19 at 17:29

Check for the ObjectProperties of your method.

If the configurable attribute is set to true, you can try using Object.defineProperty():

Object.defineProperty(store['customerData'], 'isValid', {writable: true});
// And then put your code
store.customerData.isValid = jest.fn().mockResolvedValue(true);

If it's set to false, I'm afraid I don't have any solution. I had a problem close to yours a few months ago (that I did not resolve) and I asked a question on SO, you can check what I tried, see if anything works for you: Override Object Property for unit testing purposes

jest - how to avoid using a spy for a getter

1 Answers1