How to cover Catch block in ApexUnitTest class when using DML statement in try body

Question

I have some apex code, where I try to upsert a list of records:

try {
       upsert recordList Accounts;
} catch (DmlException e) {
            //do a loooot of stuff in order to provide a proper error message
            //which will be returned to the component
  }

Now I built two test scenarios in its respective test class.

The one will be able to upsert the list. Works fine of course.

The other one (which is supposed to cover the catch block) won't because I porpously try to add duplicate values for a unique field. But instead of covering the catch block, the test class run will result into a failed one, becuase it will run into a System.AuraHandledException: Script-thrown exception and return the catch blocks error message in the dev console log, instead of happily cover the catch block.

Is there a way to do it in a cleaner way?

Answer 1

If you are trying to verify that your exception bubbles up as AuraHandledException, I typically prefer a pattern as follows:

// set up data

AuraHandledException expectedException;
Test.startTest();
    try
    {
        // do stuff
    }
    catch (AuraHandledException e)
    {
        expectedException = e;
    }
Test.stopTest();

system.assertNotEquals(null, expectedException, 'DMLException should bubble up to the Aura framework');

Answer 2

Personally I would put all the code in the catch block into a separate method that accepts the exception and any other state that is needed as its parameters (it can also return a value if required). Then I would write a unit test just for that method and not worry about the single uncovered line (the call to this method) from the catch block in the first method.

try {
    upsert recordList Accounts;
} catch (DmlException e) {
    handleException(e);
}

And:

@TestVisible
private void handleException(DmlException e) {
    //do a loooot of stuff in order to provide a proper error message
    //which will be returned to the component
}

Then write a unit test for the first method containing the upsert and a separate one for "handleException".

There are other ways to deal with this, including use of a Test.isTestRunning block in a trigger for the objects being inserted that uses some static state to determine if it should throw an exception, for example, but I don't really see the need since all that does it give you coverage on 1 extra line.

Answer 3

Further to @AdrianLarson's suggestion, the variant on this pattern that I use is:

// Set up the test data
...

try {
    // Do the stuff you want
    ...

    // Directly after where we expect an exception, add:
    System.assert(false, 'Expected an exception to be thrown');
} catch (TheExceptionTypeExpected e) {
    // Inspect the exception's details and apply any required asserts against them
    ...
} catch (Exception e) {
    System.assert(false, 'Wrong type of exception thrown: ' + e);
}

You can include the start/stop test around this as needed. What I like about this slightly more verbose structure is the ability to provide more detail and different assert messages.