this undefined in unit test of a class method

[devjared1]

I'm new to Cypress and having an issue. I'm trying to test a method of a class that refers to a parameter of the class with this.parameter but the test is failing stating that this is undefined. I'm using cy.spy(object, 'methodName') to mock the method and call it. Any help is much appreciated!
The class:

Test file:

Error:

[bahmutov]

You are not preserving the this correctly when calling the method via function. See bahmutov/cypress-examples@c0d239d and https://youtu.be/g_7LZXuEIMA