Using Chai and Jest assertions together with Jest's expect (thanks Ruben Oostinga!)

setup.js

import chai from 'chai';
import sinonChai from 'sinon-chai';
import chaiAsPromised from 'chai-as-promised';
import chaiEnzyme from 'chai-enzyme';

chai.use(sinonChai);
chai.use(chaiAsPromised);
chai.use(chaiEnzyme());

// Make sure chai and jasmine ".not" play nice together
const originalNot = Object.getOwnPropertyDescriptor(chai.Assertion.prototype, 'not').get;
Object.defineProperty(chai.Assertion.prototype, 'not', {
    get() {
        Object.assign(this, this.assignedNot);
        return originalNot.apply(this);
    },
    set(newNot) {
        this.assignedNot = newNot;
        return newNot;
    }
});

// Combine both jest and chai matchers on expect
const jestExpect = global.expect;

global.expect = actual => {
    const originalMatchers = jestExpect(actual);
    const chaiMatchers = chai.expect(actual);
    const combinedMatchers = Object.assign(chaiMatchers, originalMatchers);
    return combinedMatchers;
};

You need also add a loop at the end of the file to copy additional static methods. Just fixed the bug today related to jest-styled-components.

Object.keys(jestExpect).forEach(
  key => (global.expect[key] = jestExpect[key])
);