MSTest Unit Test - handling exceptions

Question

I have a C# unit test using Selenium WebDriver to test to see if a link exists. Here's the code:

   [TestMethod()]
    public void RegisterLinkExistTest()
    {
        IWebElement registerLink = genericBrowserDriver.FindElement(By.PartialLinkText ("Register1"));
        Assert.AreEqual("Register here", registerLink.Text, "Failed");
    }

I wanted to see what happens if I set the PartialLinkText as "Register1" instead of "Register". MSTest failed this test with a exception thrown from Selenium. I wanted the Assert.AreEqual to execute but MSTest throws a exception on the previous line. I know I can use ExpectedException attribute to specify "OpenQA.Selenium.NoSuchElementException" but I don't want to do that way because I'm not expecting that exception. How do I go about handling this?

It's not clear, you obviously know it should not exist and thus you'll get an exception. Thus the test is behaving as expected. — AD.Net, Oct 11 '12 at 23:28
I don't want MSTest to throw a unhandled exception in this case. For example, if I was looking for a correct link "Register" and the site didn't had it, how would I make the code don't throw unhandled exception but instead execute the Assert statement? — user1739627, Oct 12 '12 at 03:00

chaliasos · Accepted Answer · 2012-10-12T20:47:20.360

As @AD.Net already said, your test is working as expected.

You could catch the exception in case the link was not found but I don't see the point to do that. If the link is not found then the registerLink will be null. What's the point of asserting on a null object's property?

Your test works fine, just delete the Assert line.

However, if you also want to test the link's text try the following code:

[TestMethod()]
public void RegisterLinkExistTest()
{
    try
    {
        IWebElement registerLink = genericBrowserDriver.FindElement(By.PartialLinkText ("Register1"));
        Assert.AreEqual("Register here", registerLink.Text, "Register's link text mismatch");
    }
    catch(NoSuchElementException)
    {
        Assert.Fail("The register link was not found");
    }
}

EDIT

You can seperate your test, the first test will check if the link exists and the second will assert it's properties.

[TestMethod()]
public void RegisterLinkExistTest()
{
    IWebElement registerLink = genericBrowserDriver.FindElement(By.PartialLinkText ("Register1"));
}

[TestMethod()]
public void RegisterLinkTextTest()
{
    IWebElement registerLink = genericBrowserDriver.FindElement(By.PartialLinkText ("Register1"));
    Assert.AreEqual("Register here", registerLink.Text, "Register's link text mismatch");
}

Then use an OrderedTest and add them in that order so the RegisterLinkExistTest will be executed first. If it fails then the second test will not run.

Excellent reply. But, one quick question. I have read articles that don't recommend adding a try...catch block to unit tests. Having said that, can I check to see if the FindElement method returns null and then do a Assert.Fail? — user1739627, Oct 12 '12 at 19:09
Well, at first, I think that your test is not a unit test, but an automated GUI test. The `FindElement` method will never return null, it will always throw exception if your link is not found. What you can do is to seperate the two tests, the first one will check if the link exists and the second will assert it's properties. Then use an [OrderedTest](http://msdn.microsoft.com/en-us/library/ms182631(v=vs.100).aspx) to execute them one after the other. If the first fails the second will not be executed. I can post it in my answer if you want more details. — chaliasos, Oct 12 '12 at 19:45

MSTest Unit Test - handling exceptions

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