bit 142:programming & data structures in c#. what is unit testing? 2

BIT 142:Programming & Data Structures in C#

What is Unit Testing?

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Unit Testing (Definition)• “To write test cases for every non-trivial

function or method in the module so that each test case is [as] separate from the others [as] possible.”www.discovercomputers.info/ComputerSecurity/glossary.html

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Example Function To Test• public bool isPrime( int num){ /*implementation omitted*/}

• Definition of a prime number:– “A prime number (or a prime) is a

natural number which has exactly two distinct natural number divisors: 1 and itself.” (Wikipedia)

• “The number 1 is by definition not a prime number”

http://en.wikipedia.org/wiki/Natural_number

http://en.wikipedia.org/wiki/Divisor

http://en.wikipedia.org/wiki/1_(number)

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Example Unit Tests• public bool isPrime( int num){ /*implementation omitted*/}

• Test with:– small primes (2, 3, 5, 7, 11)– large primes– non-primes (1, 4, 9, 12, 11*17)– zero– negative numbers

Using NUnit

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What is NUnit?

• A free, open-source framework to help people create their own unit tests.

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NUnit’s Goal(s):

• Make it quick and easy

to create unit tests,

and to run those tests,

and to get a list of which tests passed/failed.

How do I Use NUnit?

• For this class, you will NOT be required to create your own Unit Tests.

• You ARE required to write software that passes tests that are provided to you, by the teacher

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How do I Use NUnit?

• You will download a starter project, which includes all the NUnit materials

• A quick example of how this all will work will follow this slide

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Demo:

• Quick walkthrough of how to use this– (GUI , Normal console, grade gen)

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Demo:• Things you’ll need / find useful:

– To select which project will be run:• Right-click on a PROJECT, then select "Set Startup

Project"

– EditFind And ReplaceFind In Files• This will let you search ALL files for a particular string

– How to get VS to comment/uncomment a block

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Workflow• Student Workflow:

– Download starter project– Examine first exercise, in Word .DOC

• Figure out which tests are used in the exercise

• Run tests, figure out which ones have failed

• Write code to make one (or more) tests pass– Repeat until all tests pass

• Repeat until all exercises done

– DELETE DIRECTORIES ON NEXT SLIDE!!!– Hand in PCEs

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Submitting Your Work• Delete the directory named

DELETE_THIS_and_bin_and_obj_folders

• DELETE bin AND obj directories!!!

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Workflow• Instructor workflow:

– Run tests to get basic grade– Double-check code– Grade for feedback/ stuff that’s not auto-

graded– Finalize grade & email gradesheets

BIT 142: Intermediate Programming 16

• Select “01_PCE_Test_Runner” as startup project– Make sure that in RunTests.cs, the lineint doThis = RUN_TEST_IN_GUI; is uncommented

– Run in VS, then click the ‘Run’ button in Nunit– NUnit should auto-reload the code when you

recompile

Details: GUI Test Runner

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• Be careful about which test(s) you’ve selected

• Note the ‘Text Output' tab– Especially for the BubbleSort exercise– Since the BubbleSort uses randomly generated

arrays, you may not get the same array twice

Details: GUI Test Runner

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Details: Normal Console Program

• Select “03_PCE_StudentCode” as startup project & run like normal

• The 'split file' thing:– Student_Answers.cs contains the code you will

write, INCLUDING main!!

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Details: Normal Console Program

• Because the test code is in another project, you MUST make your classes PUBLIC in the StudentCode project

• This will either have been done for you, or else we’ll cover how to create your own classes in C#


• Select “PCE_Test_Runner” as startup project– Make sure that in RunTests.cs, the lineint doThis = RUN_TESTS_UNDER_DEBUGGER; is uncommented

– Put a breakpoint in the test (or your code)– Run in VS

• you MUST choose DebugStart Debugging

– Useful features:• Step, Step Into, Step Out

• Watch windows

Details: Using The Debugger

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• Select “PCE_Test_Runner” as startup project– Make sure that in RunTests.cs, the lineint doThis = PRODUCE_GRADESHEET; is uncommented

– Run in VS– Everything should run, and the gradesheet should

pop up in a web browser

Details: Generating A Gradesheet

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• Note about grading output:– Not all tests that you can see in the GUI are

graded– Failed tests are big, but passed tests are kinda

small & on the bottom


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• Note that compromising the system in any way will get you a zero – Hacking/changing/disabling tests– WRITING CODE TO PASS A TEST, DESPITE

NOT ACCOMPLISHING IT’S REAL GOAL• Ex: A ‘FindInArray’ method that just asks “Did I get

asked to find the value 8? If so, return true”, so that it passes the test which asks “Is 8 in the array?”


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• Note about grading output:– Not all tests that you can see in the GUI are

graded– Failed tests are big, but passed tests are kinda

small & on the bottom


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• Located in the 02_PCE_ForTests project, inside the PCE_Test.cs file

• You should never need to change or modify these– We’ll go through them now, briefly, in order to

make sure you’ve gotten a quick overview of how the NUnit tests work.

– If you need to disable a test, you can just comment the whole method out, and the rest of the system *should* just work

Details: NUnit tests

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Understanding The NUnit Tests

• Attributes:– [Test]

• Specifies that test will be automatically called by NUnit.

• How the name shows up in the GUI

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• Attributes to ignore:– [Category] – ignore this– [TestFixture], [TimeOut], [Description] –

ignore these• Point out that the class to be tested MUST be

public!!

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• Execution of a test:– Just like normal, it will be top to bottom– If the function crashes (or throws exception),

then the crash will be caught, prevented (normally), and the test will fail

– We can also tell NUnit to check that certain things are true at certain points, and fail if they’re not true

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• Assert.That( false, “message” );

– What this does

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• bool correctAnswer = false;

• Assert.That(correctAnswer, “message” );

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• int num = 10;

• Assert.That( num == 12, “message”);

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• “Message” can work like Console.WriteLine:

• int num = 10;

• Assert.That( num == 12, “num={0} isn’t what we expected”, num);

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• More Attributes:– [Values()] – on a parameter

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• More Attributes:– [TestCase]

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• Console stuff:– Stealing Console.In– Capturing Console.Out

• Importance of the ‘fuzzy’ string comparison

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Exercises:

• Drop existing, working code into a unit test, and watch the tests work– Look at a couple of simple tests– Go through & fiddle with test code, in order to

learn it

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bit 142:programming & data structures in c#. what is unit testing? 2

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