Why can't I simulate an event in Enzyme?

Question

Unit testing

I made a form in React using Formik and Material-UI. There is one field "Card number" in the form. If you enter the number correctly and press the button, you will receive the message “Card added”: this is done through the state.
I am writing a unit test using Jest and Enzyme. Does not pass the test, which simulates data entry and button press. The error is the following:

Method “simulate” is meant to be run on 1 node. 0 found instead

but the field and the button are there, and it's even been tested. What is the problem? Please help me fix it.
I googled the error, saw a lot of advice, but I did not find a solution for myself.
Sandbox

Answer 1

Judging by the text of the error, Enzyme did not find the component on which you want to simulate the callback. There can be two reasons: either you misspelled the selector, or the name of the component when rendering does not look like what you think. To find the error, try typing wrapper.debug() to the console and see what the render looks like, maybe you will find something interesting. Well, in any case, try to give the component an id and search by it, it usually works.