Frontend web unit tests and functional/integration tests are both types of tests that are used to ensure that a web application is working correctly, but they serve different purposes and test different aspects of the application.
Frontend web unit tests are used to test the individual units of code that make up a web application, such as individual JavaScript functions or React components. These tests are typically written using a testing framework such as Jest or Mocha and are run in a simulated browser environment (e.g. JSDOM) or using headless browser (e.g. Puppeteer) . They are focused on testing the logic and behavior of individual units of code, and are typically fast to run.
Functional/integration tests, on the other hand, are used to test the overall functionality of the web application. They are focused on testing how the different units of code work together to create a cohesive user experience. These tests are typically written using a testing framework like Cypress or Selenium, and are run using a real browser. They are focused on testing the interactions between the different parts of the application, and are typically slower to run than unit tests.
In summary, unit tests are focused on testing the individual units of code while functional/integration tests are focused on testing the overall functionality of the web application, how the different units of code work together. Unit tests tend to be faster to run and are focused on specific pieces of code, while functional/integration tests tend to be slower to run and focus on overall functionality and user experience.