ViewState.test.tsx

describe('ViewState', () => {
  test('default state', () => {
    const viewState = new ViewState();
    expect(viewState.showSomething).toBe(false);
  });

  test('toggleShowingSomething()', () => {
    const viewState = new ViewState();
    viewState.toggleShowingSomething();
    expect(viewState.showSomething).toBe(true);
    viewState.toggleShowingSomething();
    expect(viewState.showSomething).toBe(false);
  });
});

ViewState.ts

class ViewState {
  @observable
  showSomething: boolean = false;

  toggleShowingSomething() {
    this.showSomething = !this.showSomething;
  }  
}

@psalv, I agree tests aren't adding value here. But they're also super simple to write and pave the way for future good behaviours. Thoughts?