I get the following message when checking the challenge for the "Testing Apex Triggers" section:

"Challenge Not yet complete... here's what's wrong: 
No Apex test class named 'TestRestrictContactByName' was found"

I've verified that there is a public class with this exact name. What am I missing?
 

@isTest
public class TestRestrictContactByName {
    public static testMethod void TestRestrictContactByNameTrigger(){
        Contact c = new Contact(LastName = 'INVALIDNAME');
    Test.startTest();
        Database.SaveResult result = Database.insert(c,false);
        Test.stopTest();
        
        System.assert(!result.isSuccess());
    }

The class is visible to all user profiles.