Mocha is a test framework to run tests.
Chai is an assertion library and you can find full documentation in the following link.
There are three type of assertion libraries in Chai.
should use the same chainable language to construct assertions.
Assume that expect library is used like below
expect(firstName).to.be.a('string'); expect(firstName).to.equal('kenan'); expect(firstName).to.have.lengthOf(5); expect(beverages).to.have.property('tea').with.lengthOf(3);
Above code could be written with should library like below.
firstName.should.be.a('string'); firstName.should.equal('kenan'); firstName.should.have.lengthOf(5); beverages.should.have.property('tea').with.lengthOf(3);
You can find more detailed usage with Express, Mocha and Chai in the following repository