Setting a mockFunction through context on a class based component with jest and enzyme

I have a very simple class based component. Which looks like the following:

class MyComponent extends React.Component {
    onPressButton () {
        console.warn('button pressed')
        const { contextFunction } = this.context
        contextFunction()
    }

    render () {
        return (
            <div>
                My Component
                <button onClick={() => onPressButton()}>Press button</button>
            </div>
        )
    }
}


MyComponent.contextType = SomeContext

That is all fine and well and works as expected. However, I am having trouble adding unit tests with jest and enzyme. My current code looks as follows:

test('should render test Press button', async () => {
    const contextFunctionMock = jest.fn()
    const wrapper = shallow(<MyComponent {...props} />)
    wrapper.instance().context = { contextFunction: contextFunctionMock }

    console.log('wrapper.instance()', wrapper.instance())

    await wrapper.instance().onPressButton() // this works just fine
    expect(contextFunctionMock).toHaveBeenCalled() // this errors, basically because ti complains contextFunction is not a function
})

As you can see above, I console.logged my wrapper.instance() to see what is going on. Interestingly enough, the context on the root of the instance object is indeed what I expected it to be based on setting the context, which is something like:

context: {
        contextFunction: [Function: mockConstructor] {
          _isMockFunction: true,
          getMockImplementation: [Function (anonymous)],
          [...Other mock function properties]
        }
...

However, there is a second context, which is in the updater property of the wrapper.instance(), and it is an empty object. Basically looks like the following:

updater: <ref *2> Updater {
        _renderer: ReactShallowRenderer {
          _context: {},
          ...
        }

Not exactly sure if this is the context being used for my component's unit test, but it is currently just an empty object, which makes me think this may be the one being used for it.

Anyway, how can I properly mock my context functions to run on this particular unit tests? Also, why is this happening but does not happen in others with a similar set of circumstances?

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