ReactJS test: How to test a component function been called when componentDidMount?

I have a component MyComponent and I would like to test the following use case:

It should call updateSomething() when component on mount

And I've come up with the following code:

System Under Test (SUT)

export class MyComponent extends React.Component<Props, State> {
    public componentDidMount() {
        console.log("componentDidMount"); // Debug purpose.
        this.fetchSomething()
            .then(() => {
                console.log("fetchSomething"); // Debug purpose.
                this.updateSomething();
            });
    }

    // These are public for simplicity
    public async fetchSomething(): Promise<any> { }
    public updateSomething() {
         console.log("updateSomething"); // Debug purpose.
    }
}

Test

it("should update something, when on mount", () => {
    const props = { ...baseProps };
    sinon.stub(MyComponent.prototype, "fetchSomething").resolves();
    const spy = sinon.spy(MyComponent.prototype, "updateSomething");

    shallow(<MyComponent {...props} />);

    sinon.assert.calledOnce(spy);
});

The result is the test failed with AssertError: expected updateSomething to be called once but was called 0 times but all three console.log() printed.

My understanding is since I want to test the event when on mount, I have to spy/stub it before it's even created, therefore I have to spy on MyComponent.Prototype. Also, for fetchSomething(), I have to stub the async call and make it .resolves() to let it progress.

But I couldn't understand how it can still console.log("updateSomething") without being spied.