PROG8060_Lesson02_DebuggingRNHEdits.pptx

Debugging doc

1. Debugging PROG8060 Developing Quality Applications Spring 2020 Baljeet S. Bilkhu [email protected] Revised: [email protected] .ca

2. Today’s Agenda… From the Course Outline: 1.0 Background and relevance of Computing Systems in Software Development 1.3 Identify the key methods and techniques used in debugging computer applications. 1.4 Identify the key components and building blocks of developing algorithms. Agile – Product Vision, Product Objectives, Product Roadmap Project Work – Project Selection, Project Proposal Development

3. What is Debugging? From Wikipedia : The process of finding and resolving defects or problems within a computer program that prevent correct operation. In other words, computer programs rarely work on their very first attempt at execution Once we find that the program is not working correctly, we need to take steps to resolve the issue(s)

4. Debugging Process

5. Reproducing the Defect Once a defect has been noted, the next task is to clearly identify how it can be reproduced… For the ProSum V 1.0 application, there is a way to make this program crash  Try large numbers (say 5 digits or more) Not all 5 digit numbers will cause a crash!

6. Reproducing the Defect ( cont …) Often times, a customer may call in to say that they experienced a crash of an application, but it may not be reproducible again or in another environment (say when the development / testing team tries) Factors that can influence whether a defect is reproducible Actual steps used to reproduce Actual environment – including hardware, software Maybe even the time of day!

7. Narrowing Down The Problem After reproducing the defect, the next area to focus on is to narrow down the problem to the minimum amount of steps or precise data values used For the ProSum V 1.0 application, there is a precise way to make this program crash Have 32768 and 32767 (sum 65535) as the minimum

8. Narrowing Down The Problem ( cont …) Often times, we’ll need to use the “divide and conquer” approach to problems to narrow down the exact cause If we have a large set of data (such as in ProSum ), we can continue to divide the data set into two until we get the exact values. Testers / Developers can also try to remove various components (UI, Business Logic, Database) to continue to narrow down where the issue exists.

9. Tracing to the root of the problem Once, the minimum number of steps are determined, debugging tools can be used by the development / testing team to determine the exact cause of the defect These debugging tools can show the exact values of variables, contents of memory (heap and stack), as well as performance metrics and other key aspects.

10. Debugging Techniques - Breakpoints One key (and simplest) technique in debugging code (using Visual Studio, C#) is called using a Breakpoint Inserting a breakpoint where we want to start debugging Using “F10” to Step Over the code or “F11” to Step Into the code Step Over: for that code that you know is functioning Step Into: for that code that you have suspicions that it is not working Can also hit the pause button when the application is running and then see the values of the variables, etc …

11. Breakpoint - Example Click to the <left> of the line number where you want to add a Breakpoint:

12. Breakpoint – Example cont … Program here does not give any error…however, it doesn’t show the correct result either 

13. Breakpoint – Example cont … Run the program:

14. Breakpoint – Example cont … Hovering over any variables will give us the value of it

15. Breakpoint – Example cont … Next, press the F11 key to “Step Into” each line of code after the breakpoint.

16. Breakpoint – Example cont … To remove the Breakpoint, simply click on the red dot that is beside the line number:

17. Breakpoint – Other Information Other information that could be valuable when debugging while using a BreakPoint : Call Stack Window: will show which part of the code is calling a particular method as well as the sequence of access (for example, if you have multiple parts of the code calling the same method, they each could be changing values that you were not expecting); Locals Window: displays the current values of all variables declared locally in the method.

18. Conditional Breakpoints These are useful debugging techniques that can break when (for instance) a particular variable takes on a specific value. (This may not be present in Visual Studio Express versions)

19. Conditional Breakpoints ( cont …) Set your breakpoint (as you normally would); Right click on the breakpoint and select “Conditions…”

20. Conditional Breakpoints ( cont …) Set your condition – in this case, let’s set i equal to four

21. Conditional Breakpoints ( cont …) See that the red dot changes to include a “+”

22. Conditional Breakpoints ( cont …)

23. Breakpoint – Hands On Work Copy the following code into a new project and set a BreakPoint at: static string titleAdd = "The sum of the numbers 11 and 22 is:"; use F11 to step into the code, keeping an eye out on each variable. class Program { static string titleAdd = "The sum of the numbers 11 and 22 is:" ; static void CalculateSum () { int firstNumber = 11; int secondNumber = 22; int sum = firstNumber + secondNumber ; Console .WriteLine (sum); } static string titleProduct = "The product of the numbers 33 and 44 is:" ; static void CalculateProduct () { int thirdNumber = 33; int fourthNumber = 44; int product = thirdNumber * fourthNumber ; Console .WriteLine (product); } static void Main() { Console .WriteLine ( titleAdd ); CalculateSum (); Console .WriteLine ( titleProduct ); CalculateProduct (); Console .ReadLine (); } }

24. Try – Catch Blocks To avoid unexpected program crashes and to generate meaningful responses for errors, we can use try-catch blocks. When an error is encountered, the code in the try section is skipped and execution resumes in the catch section. try { using (var myObject = new MyClass ()) { // Actual code is here } } catch ( Exception ex) { // How to handle an exception here }

25. Try – Catch Block - Example

26. Try – Catch Block – Example ( cont …)

27. Try – Catch Block – Example ( cont …)

28. Logging Data When working with large programs (say, hundreds or thousands of lines of code), it may be difficult to find exactly where the error occurred C# allows the ability to output text to a log file using the StreamWriter class (in the System.IO namespace)

29. Logging Data

30. Developing Algorithms As we can recall, Algorithms are simply instructions or a set of steps for completing a task or problem. We can take this definition to add the words “…in an efficient method or manner” If we’re able to devise a set of steps that is more efficient than another set of steps to solve the same problem, we will be able to make the most of the finite resources (say CPU, Memory, Network, Disk, etc …) that are at our disposal.

31. Developing Algorithms ( cont …) For instance, if we are given the problem “add all integers from 0 to 4 and show the result”, we can develop the solutions as follows: Solution A Solution B Var1 = 0; Var2 = 1; Var3 = 2; Var4 = 3; Var5 = 4; Sum = Var1 + Var2 + Var3 + Var4 + Var5; Print (Sum); Sum = 0; For i in range(4): Sum += I Print (Sum);

32. Building Blocks of Algorithms The key building blocks of Algorithms: Sequence / Action Selection / Decision Iteration / Loop

33. Building Blocks of Algorithms The key building blocks of Algorithms: Sequence / Action For example, sum var1 and var2 Selection / Decision If the temperature is greater than 27C, then print “it is hot outside” Iteration / Loop Calculate the sum of all even numbers from zero to one-hundred

34. Building Blocks of Algorithms – Class Work Print the name of your best friend Compute the area of a circle with a radius of 5cm Print the conversion equivalents of 0 to 100 from mph to km/h If Jack is taller than Jill, then print “Jack is taller” Print the square root of all integers between 0 and 49

35. Agile

36. Product Vision This is usually the first stage in any Agile project – defining the Product Vision – essentially an “elevator pitch” about what your product is and how it will support your overall company’s vision / objectives

37. Product Objectives Focus is applied on developing / defining: Goals of the product Intended Customers Need Competition Distinctive Differences

38. Product Roadmap Provides an overall view of all of the product’s requirements Categorizes requirements into logical groupings Estimates the effort required Outlines what features will be delivered at what point in time Agile Best Practices: Road Maps Video

39. Definition of Done (DoD) Within Agile, each iteration or Sprint should deliver some part or increment of the overall product with a focus on increasing the quality, functionality or overall completeness. The Definition of Done (DoD) is a definition that each team / project group will define as to what they consider as being “Done” for that particular sprint, iteration, or release. It may be something as simple as “all unit tests must pass”

40. Project Work

41. Task 2: Preparing Your Proposal Develop a Project Proposal using the template provided in eConestoga for this week. Due on Friday at the end of the Lab One submission per group / team Worth 5% of your overall project mark – deductions will apply for any late / absentees Need to include: Project Background and Description Problem Statement Project Scope High-Level Requirements Materials, Tools Required References Used

42. Thank You ! Any questions?