How to handle new window, which opened automatically in new tab?

My test code do thomething, then automatically opening new tab and in a new tab automatically opening new window (not a tab).

When I use this code: driver.getWindowHandles() it is returns 2 tab ID instead 3 tab ID.

If it's a new window to count the number of WindowHandles you need to induce WebDriverWait for numberOfWindowsToBe(2) and you can use the following code block:

String mainWindowHandler = driver.getWindowHandle(); // store mainWindowHandler for future references
//line of code that opens a new TAB / Window
new WebDriverWait(driver, 5).until(ExpectedConditions.numberOfWindowsToBe(2));  //induce WebDriverWait
Set<String> handles = driver.getWindowHandles(); 
Iterator<String> iterator = handles.iterator(); 
while (iterator.hasNext()) 
{ 
    String subWindowHandler = iterator.next(); 
    if (!mainWindowHandler.equalsIgnoreCase(subWindowHandler))
    {
        driver.switchTo().window(subWindowHandler);
    }
}

References

You can find a couple of relevant detailed discussions in:

• Selenium switch focus to tab, which opened after clicking link
• Best way to keep track and iterate through tabs and windows using WindowHandles using Selenium
• org.openqa.selenium.WebDriverException: invalid argument: 'handle' must be a string while window handling with Selenium and Java in Linux