setState.md

.setState(nextState[, callback]) => Self

A method to invoke setState() on the root component instance, similar to how you might in the methods of the component, and re-renders. This method is useful for testing your component in hard-to-achieve states, however should be used sparingly. If possible, you should utilize your component's external API (which is often accessible via .instance()) in order to get it into whatever state you want to test, in order to be as accurate of a test as possible. This is not always practical, however.

NOTE: can only be called on a wrapper instance that is also the root instance.

Arguments

1. nextState (Object): An object containing new state to merge in with the current state
2. callback (Function [optional]): If provided, the callback function will be executed once setState has completed

Returns

ShallowWrapper: Returns itself.

Example

class Foo extends React.Component {
  constructor(props) {
    super(props);
    this.state = { name: 'foo' };
  }

  render() {
    const { name } = this.state;
    return (
      <div className={name} />
    );
  }
}

const wrapper = shallow(<Foo />);
expect(wrapper.find('.foo')).to.have.lengthOf(1);
expect(wrapper.find('.bar')).to.have.lengthOf(0);
wrapper.setState({ name: 'bar' });
expect(wrapper.find('.foo')).to.have.lengthOf(0);
expect(wrapper.find('.bar')).to.have.lengthOf(1);

Related Methods

• .setProps(props[, callback]) => Self
• .setContext(context) => Self