Building unit tests correctly with visual studio 2013

Building Unit Tests correctly with VS 2013

About.ME
• Senior Consultant @CodeValue
• Developing software (Professionally) since 2002
• Mocking code since 2008
• Test driven professional
• Blogger: http://blog.drorhelper.com

/*
* You may think you know what the following code does.
* But you dont. Trust me.
* Fiddle with it, and youll spend many a sleepless
* night cursing the moment you thought youd be clever
* enough to "optimize" the code below.
* Now close this file and go play with something else.
*/
//
// Dear maintainer:
//
// Once you are done trying to 'optimize' this routine,
// and have realized what a terrible mistake that was,
// please increment the following counter as a warning
// to the next guy:
//
// total_hours_wasted_here = 42
//

//This code sucks, you know it and I know it.
//Move on and call me an idiot later.
http://stackoverflow.com/questions/184618/what-is-the-
best-comment-in-source-code-you-have-ever-encountered
We fear our code!
//Abandon all hope ye who enter beyond this point
//When I wrote this, only God and I understood what I was doing
//Now, God only knows
// I dedicate all this code, all my work, to my wife, Darlene, who will
// have to support me and our three children and the dog once it gets
// released into the public.
//The following 1056 lines of code in this next method
//is a line by line port from VB.NET to C#.
//I ported this code but did not write the original code.
//It remains to me a mystery as to what
//the business logic is trying to accomplish here other than to serve as
//some sort of a compensation shell game invented by a den of thieves.
//Oh well, everyone wants this stuff to work the same as before.
//I guess the devil you know is better than the devil you don't.

“If we’re afraid to change
the very thing we’ve
created,
we failed as professionals”
Robert C. Martin

“Code without tests is bad code...
With tests, we can change the
behavior of our code quickly and
verifiably...”
Michael Feathers - “Working effectively with legacy code”

This is a unit test
[Test]
public void CheckPassword_ValidUser_ReturnTrue()
{
bool result = CheckPassword(“user”, “pass”);
Assert.That(result, Is.True);
}
D

This is also a unit test
[TestMethod]
public void CheckPassword_ValidUser_ReturnTrue()
{
bool result = CheckPassword(“user”, “pass”);
Assert.IsTrue(result);
}
D

A unit test is…
1. Tests specific functionality
2. Clear pass/fail criteria
3. Good unit test runs in isolation

Unit testing is an iterative effort
Unit testing is an iterative effort

There’s more to unit tests then just “tests”
Written by the developer who wrote the code
Quick feedback
Avoid stupid bugs
Immune to regression
Change your code without fear
In code documentation

13
copyright 2008 trainologic LTD
13
One last reason
You’re already Testing your code – manually
So why not save the time?

The cost of unit testing
120%
135%
115%
125%
0%
20%
40%
60%
80%
100%
120%
140%
IBM: Drivers MS: Windows MS: MSN MS: VS
Time taken to code a feature
WithoutTDD Using TDD

The value of unit testing
61%
38%
24%
9%
0%
20%
40%
60%
80%
100%
120%
140%
IBM: Drivers MS: Windows MS: MSN MS: VS
Using Test Driven Design
Time To Code Feature Defect density of team
Major quality improvement for minor time investment

The cost of bugs
0
1
2
3
4
5
6
7
8
9
10
0%
20%
40%
60%
80%
100%
Thousand$s
%defectscreated
Where does it hurt?
% of Defects Introduced Cost to Fix a Defect
The pain is here! This is too late…

Supporting environment
• The team
• Development environment

The Team
• The team commitment is important
• Learn from test reviews
• Track results

Tools of the trade
Server Dev Machine
Source
Control
Build Server
Test Runner
Code
CoverageBuild Script
Unit Testing
Framework
Isolation
Framework

Development environment
• Make it easy to write and run tests
– Unit test framework
– Test Runner
– Isolation framework
• Know where you stand
– Code coverage

Unit testing frameworks
• Create test fixtures
• Assert results
• Additional utilities
• Usually provide command-line/GUI runner
http://en.wikipedia.org/wiki/List_of_unit_testing_frameworks

[Test]
public void AddTest()
{
var cut = new Calculator();
var result = cut.Add(2, 3);
Assert.AreEqual(5, result);
}
This is not a real unit test

Real code has dependencies
Unit test
Code under test
Dependency Dependency

The solution - Mocking
Fake object(s)
Unit test
Code under test
Dependency

Isolation
• Replace production logic with custom logic
• We do this in order to
– Focus the test on one class only
– Test Interaction
– Simplify Unit test writing

What Mocking framework can do for you?
• Create Fake objects
• Set behavior on fake objects
• Verify method was called
• And more...

[Test]
public void IsLoginOK_LoggerThrowsException_CallsWebService()
{
var fakeLogger = Isolate.Fake.Instance<ILogger>();
Isolate
.WhenCalled(() => fakeLogger.Write(""))
.WillThrow(new LoggerException());
var fakeWebService = Isolate.Fake.Instance<IWebService>();
var lm = new LoginManagerWithMockAndStub(fakeLogger,fakeWebService);
lm.IsLoginOK("", "");
Isolate.Verify.WasCalledWithAnyArguments(() => fakeWebService.Write(""));
}

Open source
• FakeItEasy
• Moq
• NMock3
• nSubtitute
• Rhino
Mocks
Free
• MS Fakes
Commercial
• Isolator
• JustMock

Moq
45%
Rhino Mocks
23%
None
9%
FakeItEasy
6%
Nsubstitute
6%
Isolator
4%
Moles
2%
MS Fakes
2%
JustMocks
2%
Other
1%
http://osherove.com/blog/2012/5/4/annual-poll-which-isolation-framework-do-
you-use-if-any.html

Code Coverage
So, What is a good code coverage?

Source Control
Build Server
Commit
There you go
What’s new?
Build Agents
We automatically get
•Error reports & logs
•New version installer
•Help files
•More…

How I failed unit testing my code
Unit testing is great!
Everything should be tested
I can test “almost” everything
Tests break all the time
Unit testing is a waste of time 

A good unit test should be:
• Easy to understand
• Trustworthy
• Robust
Trust Your Tests!

Trustworthy means deterministic
Problem
• I cannot re-run the exact same test if a test fails
Solution
• Don’t use Random in tests
– If you care about the values set them
– If you don’t care about the values put defaults
– Do not use Sleep & time related logic – fake it
• Use fake objects to “force” determinism into the test
• When possible avoid threading in tests.

Trustworthy also means not fragile
Ideally
A test would only fail if a bug was introduced
OR
Requirements changed

How to avoid fragile tests
• Don’t test private/internal (most of the time)
• Fake as little as necessary
• Test only one thing (most of the time)

Readable unit tests
Unit test intent should be clear!
1.What is being tested?
2.What is the desired outcome?
3.Why did test fail?

Learn to write “clean tests”
[Test]
public void CalculatorSimpleTest()
{
calc.ValidOperation = Calculator.Operation.Multiply;
calc.ValidType = typeof (int);
result = calc.Multiply(1, 3);
Assert.IsTrue(result == 3);
if (calc.ValidOperation == Calculator.Operation.Invalid)
{
throw new Exception("Operation should be valid");
}
}

Or suffer the consequences!
[Test]
public void CalculatorSimpleTest()
{
var calc = new Calculator();
var result = calc.Multiply(-1, 3);
Assert.AreEqual(result, -3);
Assert.IsTrue(result == 3);
if (calc.ValidOperation == Calculator.Operation.Invalid)
{
throw new Exception("Operation should be valid");
}
Assert.AreEqual(result, 30);
}

Writing a good unit test
[Test]
public void
Multiply_PassTwoPositiveNumbers_ReturnCorrectResult()
{
var calculator = CreateMultiplyCalculator();
var result = calculator.Multiply(1, 3);
Assert.AreEqual(result, 3);
}

So what about code reuse
Readability is more important than code reuse
• Create objects using factories
• Put common and operations in helper
methods
• Use inheritance – sparsely

Avoid logic in the test (if, switch etc.)
Problem
• Test is not readable
• Has several possible paths
• High maintain cost

Tests should be deterministic
Solution
• Split test to several tests – one for each
path
– If logic change it’s easier to update some of the
tests (or delete them)
• One Assert per test rule

How to start with unit tests
1. Test what you’re working on – right now!
2. Write tests to reproduce reported bug
3. When refactoring existing code – use unit tests to
make sure it still works.
4. Delete obsolete tests (and code)
5. All tests must run as part of CI build

Building unit tests correctly with visual studio 2013

Building unit tests correctly with visual studio 2013

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