Building unit tests correctly with visual studio 2013

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Building Unit Tests correctly with VS 2013

About.ME
• Senior Consultant @CodeValue
• Developing software (Professionally) since 2002
• Mocking code since 2008
• Test...

/*
* You may think you know what the following code does.
* But you dont. Trust me.
* Fiddle with it, and youll spend many...

//This code sucks, you know it and I know it.
//Move on and call me an idiot later.
http://stackoverflow.com/questions/184...

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

Legacy code

“Code without tests is bad code...
With tests, we can change the
behavior of our code quickly and
verifiably...”
Michael F...

$This is a unit test [Test] public void CheckPassword_ValidUser_ReturnTrue() { bool result = CheckPassword(“user”, “pass”);...$

$This is also a unit test [TestMethod] public void CheckPassword_ValidUser_ReturnTrue() { bool result = CheckPassword(“user...$

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 bug...

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
Tim...

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 T...

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 Defect...

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
Frame...

Development environment
• Make it easy to write and run tests
– Unit test framework
– Test Runner
– Isolation framework
• ...

Unit testing frameworks
• Create test fixtures
• Assert results
• Additional utilities
• Usually provide command-line/GUI ...

[Test]
public void AddTest()
{
var cut = new Calculator();
var result = cut.Add(2, 3);
Assert.AreEqual(5, result);
}
This ...

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 ...

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

$[Test] public void IsLoginOK_LoggerThrowsException_CallsWebService() { var fakeLogger = Isolate.Fake.Instance<ILogger>(); ...$

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:/...

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 v...

Build run at a Glance

How I failed unit testing my code
Unit testing is great!
Everything should be tested
I can test “almost” everything
Tests ...

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 ...

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 ...

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

Learn to write “clean tests”
[Test]
public void CalculatorSimpleTest()
{
calc.ValidOperation = Calculator.Operation.Multip...

Or suffer the consequences!
[Test]
public void CalculatorSimpleTest()
{
var calc = new Calculator();
calc.ValidOperation =...

$Writing a good unit test [Test] public void Multiply_PassTwoPositiveNumbers_ReturnCorrectResult() { var calculator = Creat...$

So what about code reuse
Readability is more important than code reuse
• Create objects using factories
• Put common and o...

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 ...

How to start with unit tests
1. Test what you’re working on – right now!
2. Write tests to reproduce reported bug
3. When ...

Building unit tests correctly with visual studio 2013