当使用assertEquals时，应该捕获哪种异常？

Question

I'm making a webdriver and part of it is to check the title to make sure that it is on the right page. Just for my benefit now I want it to show a dialog box when it the title doesn't match but right now all it does is give me an error message in the console. I believe it's my exception that is the problem. Any suggestions?

try{
    assertEquals("Current page title", "Account Inventory - Select Manager", pageTitle);
}
catch(Exception ex)
{

    JFrame frame = new JFrame("Message");
    JOptionPane.showMessageDialog(frame ,
            "The title does not match");
}

Answer 1

assertEquals with throw an AssertionError when the condition is not met. So you should probably either catch that error explicitly, or widen your catch to include Throwable rather than Exception .

See the type hierarchy diagram below to understand why catch (Exception e) won't catch an AssertionError .

java.lang.Object
  |--- java.lang.Throwable
         |--- java.lang.Error
                | --- java.lang.AssertionError  // not a descendent of Exception
         |--- java.lang.Exception

However... tests are generally supposed to be automated so I can't imagine why you'd want to introduce a human element by showing a dialog.

Answer 2

Actually, assertions are not for handling exceptions, they are for asserting some test cases. If an asserted case doesn't come to be true, then there is a serious problem with the input causing the problem which require special attention, that's why you get AssertionError when an assertion fails.

And I think you are mixing the intentions of using exceptions and errors.

Answer 3

I am assuming that this is unit test code. You can handle it in 2 ways.

1. Catch the error and write error log.
2. Do not catch the exception and to allow a method further up the call stack to handle it