1. ERROR HANDLING AND DEBUGGING
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Structured Programming: Unit 4 Slide 1

2. Objectives Write a program that uses structured exceptions.
Compare the exception hierarchy in Java with the exception hierarchy in .NET
Use a Try...Catch...Finally construct.
Throw exceptions
Create custom exceptions
Perform debugging techniques.
Identify the principles of debugging
Identify debugging strategies
Set breakpoints and step through code
Use the call stack to isolate a problem
Compare the following types of testing: Desk checking, Unit testing, Integration testing, Code reviews.
Compare and contrast black box, white box, and architectural tests
Describe the purpose of unit testing
Describe the purpose of integration testing
Design tests
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3. Exception Class Hierarchy (Java)
java.lang
java.io
Throwable
Interface
Serializable
Exception
Error
RuntimeException
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4. Exception Class Hierarchy .NET
System.Object
System.Exception
ISerializable
System.ApplicationException
System.SystemException
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5. Try…Catch…Finally Try Catch Finally Code that might throw an exception
Code to handle the exception
Finally
Cleanup code to execute when exit is normal or because of exception
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6. Standard Exception Handling Options
Log exception
Ask for input
Use default or alternate value
Forward control somewhere else
Convert the exception
Ignore the exception
Retry the action that caused the exception
Take a recovery action
Prepare to terminate
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7. Dos and Don’ts Dos Don’t Handle exceptions if you can
Handle specific exceptions specifically
Log exceptions
Convert exceptions to a business context
Don’t
Ignore an exception
Use blanket exception handling
Convert a specific exception to a general exception
Handle an exception you could avoid
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8. Custom Exceptions (Java)
Define the exception class
public class MyException extends Exception
Declare the methods as “throws CustomerException”
public void MyMethod () throws MyException
Throw the exception
Throw new MyException(“Problem”)
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9. Custom Exceptions (VB.NET)
Define the exception class
Public Class MyException Inherits Exception
Throw the exception
Throw new MyException(“Problem”)
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10. Common Misconceptions about Testing
Developers should do no testing
Developers should do all the testing
You just need to do one thing to test
You can fully test an application
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11. Types of Testing Black box White box Architectural Testers and users
Developers
Architectural
Load test
Performance test
Security test
Stress test
Usability test
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12. Improving testability
Modularize code
Use encapsulation and interfaces
Define services to relate to business behavior
Define methods that capture
State
Flow
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13. Moving to Integration Testing
Different coding styles might present an issue
More use of abstraction and encapsulation
Context and invocation order become important
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14. Debugging Principles Know your system Repeatability
Understand the differences between the bug and your system
Debugging requires testing
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15. Debugging Strategies Reproduce the bug Test around the bug
Look for differences between systems where the bug occurs and where it doesn’t
Narrow the scope
Identify the “Point of Departure”
Brainstorm with the group
Look for similar problems in bug database
Look for patterns over time
Filter your system’s output
Simulate system behavior
Monitor the system
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16. Debugging Techniques Breakpoints Stepping through code Watch window
Step into
Step over
Watch window
Call stack
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17. Summary In this unit, students learned:
How to perform structured error handling.
How to create and throw exceptions.
Methods for testing an application.
Debugging techniques.
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