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What is Unit Testing?

Writing snippets of code that try to use methods (functions) from your program.

Each snippet should test one (and only one) function......by calling the function, then comparing what the function actually produced to what it was supposed to produce.

Running the test code thus verifies that (at least part of) your program is doing

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Unit Testing (Definition)

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”

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Example Function To Test

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

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Example Test Cases

Using the NUnit-Based Autograded Projects

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A free, open-source framework to help people create their own unit tests for any .Net language◦ We’ll use it for C#

Related to (“inspired by”) JUnit◦ JUnit is for Java testing

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What is NUnit?

Make it quick and easy

to create unit tests,

and to run those tests,

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

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NUnit’s Goal(s):

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

You ARE required to write software that passes tests. The tests 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

Extract the .ZIP

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How do I Use NUnit?

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Open the Solution (.SLN) file◦ Note multiple projects

There are three projects inside the starter solution:◦ 01_PCE_Test_Runner

This contains all the (instructor-provided) code that handles running the tests.

This includes running the test in the GUI, and running the auto-grading logic

◦ 02_PCE_ForTests This is where the units tests themselves are located

◦ 03_PCE_StudentCode This is where YOUR CODE must be put

Details: Solution Setup

Ignore anything except the RunTests.cs◦ You can set the ‘mode’ here (you’ll see this later)

01_PCE_Test_Runner

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This project contains all the tests

TestHelpers.cs contains stuff that multiple tests, across multiple assignments, make use of◦ Input/output capturing code ◦ ‘Fuzzy’ comparisons

02_PCE_ForTests

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PCE_Tests_To_Run.cs contains the actual tests – you’ll want to look in here for the details of each particular test.

02_PCE_ForTests

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This is where YOUR CODE will be put.◦ There will be just one file (Student_Answers.cs)

◦ Your code (that you will hand in) always goes into Student_Answers.cs

03_PCE_Student_Code

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If you want to experiment with a normal, console application, you do so by setting this project as the startup project, and then adding code to Main.

03_PCE_Student_Code

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Demo:How to run the tests in the NUnit GUI

Make sure that “01_PCE_Test_Runner” is startup project◦ Right-click on it, and “Set as startup project” if it’s

not◦ Make sure that in RunTests.cs, the linedoThis = RUN_TEST_IN_GUI; is uncommented

In VS: DebugStart (Without) Debugging◦ (If either doesn’t work, email prof!)

In the NUnit test runner: click ‘Run’ button◦ Be careful about which test(s) you’ve selected

Details: GUI Test Runner

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NUnit should auto-reload your code when you recompile◦ If it doesn’t, you can force it to reload:

File Reload Project orFile Reload Tests

You can then leave the test runner open, switch back to Visual Studio,change your program, and re-run your tests◦ Without having to quit-and-restart NUnit

Details: GUI Test Runner

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Run the test(s) in the GUI Get the name of a test that is failing

1. Edit Find And Replace Find In Filesa) Type in the name of the failing test & go find it.

2. In 02_PCE_ForTests, in PCE_Tests_To_Run.csfind the test by hand

How to find a failing test

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Note the tabs at the bottom: Errors And Failures:

◦ Lists out the exact error message when the test failed

◦ Tries to tell you where the failure occurred Tests Not Run:

◦ This should never happen (unless there’s an error with the test)

Test Output:◦ Anything you (or the test) Console.Writes will be

displayed here

Details: GUI Test Runner

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Details: The Unit Tests

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[Test]

◦ Specifies that test will be automatically called by NUnit.

◦ The GUI automatically finds this test, and gets the name to display in the GUI

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[Test] Attribute

[Category]◦ Used by the instructor to put a test into a grading

category [TestFixture], [TimeOut], [Description]

◦ Used to tell Nunit about tests

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Attributes to ignore:

NUnit ‘magically’ finds the tests to run◦ Once the test starts, it runs just like normal code

We can tell NUnit to check that certain things are true at certain points, and fail if they’re not true◦ This is done using the Assert.That command

◦ If the function crashes (or throws exception), then the crash will be caught, prevented (normally), and the test will fail

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Execution of a test

Assert.That( false, “msg” );

What this does:◦ If the first parameter (‘false’) is false,

then the test will fail, with the message “msg”

Test: Basic_Fail in the Nunit_Demo project

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Basic (Failing) Test

bool correctAnswer = false;Assert.That(correctAnswer, “msg” );

This separates out the ‘is it correct?’ logic from the Assert statement

Notice that we can (and often will) use this pattern

◦ Test: Basic_Fail_2, Basic_Fail_3

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More typical pattern

“Message” can work like Console.WriteLine:

int num = 10; Assert.That( num == 12, “num={0} isn’t what we expected”, num);

Test: Basic_Console_WriteLine

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Using Assert Like Console.Write*

Typically, a test will call into your code, check the result, and then Assert that your answer is the same as the expected answer

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#

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Calling Student Code

This is the first ‘real’ unit test Call into your codeCheck the answerPass (or fail) the test

Test: Basic_Unit_Test

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Calling Student Code

If you’re having trouble getting a test to pass,

you can try adding print statements to your code,

so that as the program runs,

it tells you about what it’s doing

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Debugging Strategy: Printing

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Test Attribute Details

Certain tests may redirect input, output◦ This means that they can ‘feed’ input to your

code, and ‘capture’ the output that you produce

Capturing Console.Out in the Test◦ Importance of the ‘fuzzy’ string comparison

Test-Supplied Console.In

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Redirecting I/O

Using the TestHelpers software, the tests can capture output.◦ This is in the TestHelpers.cs file ; you’re welcome to

look at it, if you’re curious about how it works

Anything that you print (using Console.Write) can be captured

Test: Unit_Test_Console_WriteLine

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Output (captured by the test)

The TestHelpers software also provides for a number of helpful routines, including ‘fuzzy’ comparisons◦ ‘Fuzzy’ for strings means case-insensitive, and

without (too much) regard for blank spaces

Test: Unit_Test_Console_WriteLine_Fuzzy

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Fuzzy String Comparisons

The test can also assemble a string, which will be used as the input to your code.

Whenever you call Console.Readline, you will read everything up to the next newline◦ Enter key (Newline) in C#: \n

Example of input: ◦ “2\n3\nquit\n” is the same as typing

2<enter>3<enter>quit<enter>

Test: Unit_Test_Console_IO_Fuzzy35

Test-Supplied Input

public void Unit_Test_Values( [Values(-1, 0, 1, 10)]int valueToTry)

Tells NUnit to call this function four separate times:◦ once with valueToTry set to -1◦ once with valueToTry set to 0, ◦ once with valueToTry set to 1◦ once with valueToTry set to 10

Test: Unit_Test_Values

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[Values] Attribute

public void Unit_Test_Values_2([Values(1, 10)]int a, [Values(2, 4)]int b)

Tells NUnit to call this function with ALL POSSIBLE COMBINATIONS OF a and b:◦ a = 1, b = 2◦ a = 1, b = 4◦ a = 10, b = 2◦ a = 10, b = 4

Test: Unit_Test_Values_2

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[Values] Attribute - Combo

[TestCase( 1, 2)][TestCase( 10, 4)]public void Unit_Test_TestCase(int a, int b)

Tells NUnit to call this function with EACH TestCase: ◦ a = 1, b = 2◦ a = 10, b = 4

Test: Unit_Test_TestCase

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[TestCase] Attribute

Notice that before each test, the method marked with [Setup] will be run

In the example test, we’ll use this to initialize x to be 10, y to be 20, and ex5 to refer to an object

Test: Unit_Test_Setup

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Tests that use the [Setup] Attribute

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Demo:How to Generate a gradesheet

(including grade)

Not all tests that you can see in the GUI are neccessarily graded

Failed tests are big, but passed tests are kinda small & on the bottom

Details: Autograder

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Note that compromising the system in any way will get you a zero   ◦ Cracking/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?”

Details: Autograder

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Demo:How to run the program in normal console mode

Make sure that 03_PCE_StudentCode is the startup project◦ Right-click on the PROJECT, and choose “Set as

Startup Project” to make it the startup project

Put whatever code you want to into the main method.

Normal Console Program

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If you want, you can always create a new console solution, then copy your code into it.

Normal Console Program

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