What is the difference between a unit test and a functional/integration test?

Unit Tests are tests focused on the unit of execution (usually, the unit of code, being a function or a class method). Those types of tests are extremely useful for maintaining a strict code base that can scale and grow without major side-effects, and also for asserting input/output types of expectations.

Integration or Functional Tests are tests which are usually executed in controlled environments, such as a staging environment which can be a copy of production, and are mainly focused on finding integration bugs, meaning the whole application is tested as a whole, feature by feature, usually with the help of tools such as Selenium or such for simulating a full-fledged user of the application.

Thank you for the question,

Here is the answer: https://codeutopia.net/blog/2015/04/11/what-are-unit-testing-integration-testing-and-functional-testing/