How do you explain the concept of end-to-end testing for web applications?

End-to-end (E2E) testing of web applications is the process of verifying the operation of the entire application, from the user interface to the database and back. The goal is to ensure that all system components interact correctly and that the user scenario is executed without errors.

E2E tests typically automate user actions: navigating through pages, entering data, clicking buttons, and checking results on the screen. This helps identify issues that are not visible during unit or integration testing.

Example: for a web application in Go, tools like Selenium or Cypress can be used, which control the browser and verify interface behavior.

Example in Go using the chromedp library:

import (
    "context"
    "github.com/chromedp/chromedp"
    "log"
)

func main() {
    ctx, cancel := chromedp.NewContext(context.Background())
    defer cancel()

    var pageTitle string
    err := chromedp.Run(ctx,
        chromedp.Navigate(`https://example.com`),
        chromedp.Title(&pageTitle),
    )
    if err != nil {
        log.Fatal(err)
    }
    log.Println("Page title is:", pageTitle)
}

This test checks that the page loads and has the expected title, which is part of E2E testing.