By default focus will change newly opened window , so change your focus to old window
String winHandleBefore = driver.getWindowHandle();
// Perform the actions to.open new tab
// Switch back to original browser (first window)
driver.switchTo().window(winHandleBefore);
If it's opens in same tab,
Then
driver.manage().timeouts().pageLoadTimeout(1, TimeUnit.SECONDS);
try {
driver.get("http://url/to/my/slow/loading/page");
} catch (TimeoutException e) {
// Ignore the exception.
}
//Validate , and set pageloadtimeout to normal which is 15 mins
driver.manage().timeouts().pageLoadTimeout(900, TimeUnit.SECONDS);
Also try Page loading strategy.