Test prevProps in componentDidUpdate in React via Jest

Question

Having following code:

componentDidUpdate(prevProps: JsonInputProps) {
  if (prevProps.value !== this.props.value) {
    this.validateJsonSchema(this.props.value || '');
  }
}

and test code:

  it('componentDidUpdate should mount', () => {
    const onChange = jest.fn();
    const event = { target: { value: 'simulate-event' } };
    const wrapper = enzyme
      .shallow(<JsonInput onChange={onChange} onValueChange={mockOnValueChange}/>)
      .simulate('change', event);
    wrapper.setProps({ value: 'example' });
    expect(onChange).toBeCalled;
  });

and test coverage:

I got 'else path not taken' and I do NOT want to ignore the else path but dunno how to change props. Any idea?

Answer 1

To cover else case you can pass in same prop value along with possibly something else along with it so that it covers else case upon update.

  it('componentDidUpdate should mount', () => {
    const onChange = jest.fn();
    const event = { target: { value: 'simulate-event' } };
    const wrapper = enzyme
      .shallow(<JsonInput onChange={onChange} onValueChange={mockOnValueChange}/>)
      .simulate('change', event);
    wrapper.setProps({ foo: 'something' });
    expect(onChange).toBeCalled;
  });