CalculatorTests.cs

[Test]
public void Addition()
{
    _driver.FindElementByName("Five").Click();
    _driver.FindElementByName("Plus").Click();
    _driver.FindElementByName("Seven").Click();
    _driver.FindElementByName("Equals").Click();
            
    var calculatorResult = GetCalculatorResultText();
    Assert.AreEqual("12", calculatorResult);
}

private string GetCalculatorResultText()
{
    return _driver.FindElementByAccessibilityId("CalculatorResults").Text.Replace("Display is", string.Empty).Trim();
}