findElement By xpath not working using Selenium WebDriver

Question

I'm was trying to find the following element by xpath:

<input class="t-TextBox" type="email" test-id="test-username"/>

Then I tried:

element = findElement(By.xpath("//[@test-id='test-username']"));

This is the error Expression is not a legal expression.

Answer 1

element = findElement(By.xpath("//*[@test-id='test-username']");

element = findElement(By.xpath("//input[@test-id='test-username']");

(*) - any tagname