Test Drive Development

Test Driven Development
by Satya Sudheer

Before We Start!
4 There is just Code;
there is no good or bad.
4 Everything we are going to
discuss is already known to you!
4 Using automated feedback loops
doesn't mean no manual testing.
4 Most of them are subjective, also debatable ..

Agenda
4 Basics
4 Test Driven Development
4 Coding Kata
4 TDD Pitfalls
4 Q&A

Testing
4 Testing is an act of gaining insights.
1. Is the app is usable.
2. Whats the user experience like?
3. Does the workflow make sense?

Verification
4 Verification, on the other hand, is an act of
confirmation.
1. Does the code do what it's supposed to do?
2. Are the calculations right?
3. Regression, is the program working as excepted
after the code or config. changes?

Do manual testing to gain insights and
automated versification to influence
the design and to confrim the code
continues to meet the excpetations.

What is a "Unit Test"
"it's a situational thing - the team
decides what makes sense to be a
unit for the purposes of their
understanding of the system and
its testing." - Martin Fowler
A unit can be a method, function,
class, group of classes.

Why Do We Write Unit Tests?
4 Validate the System, Immediate Feedback
4 Code Coverage
4 Enable Refactoring
4 Document the System Behavior
4 Your Manager Told You To

How many unit test do you write?
public bool IsLoginSuccessful(string user, string password)
{
// ...
}
As part of that, we will do
4 State Verification
4 Behaviour Verification

Unit tests isolate the unit of work
from its real dependencies, such as
time, network, database, threads,
random logic, and so on.
Unit Tests runs in memory & quick!

Sociable Unit Test
4 Sociable unit testing covers
more functionality, easier to
maintain, but harder to debug.

Solitary Unit Test
4 Solitary unit testing enables
higher code coverage,
promotes decoupling; executes
faster than sociable unit
testing and enables better
software designs.

What is a Boundary?
A boundary is "a database, a queue, another system, or
even an ordinary class. if that class is 'outside' the area
your trying to work with or are responsible for"
-- William E. Caputo

Solitary unit testing motivates us
towards pure functions while allowing
us to keep the benefits of OOP.

Test Doubles (Stunt Double)
4 Dummy, just used to fill parameter lists.
4 Fake objects actually have working implementations.
4 Stubs provide canned answers to calls made during
the test.
4 Spies are stubs that also record some information.
4 Mocks are objects pre-programmed with
expectations.

Test Pyramid?
Its essential point is that you
should have many more low-level
unit tests than high level end-to-
end tests running through a GUI.
In short, tests that run end-to-
end through the UI are: brittle,
expensive to write, and time
consuming to run.

Agile Testing
Quadrants
4 Quadrant 1: Technology-facing
tests that support the team
4 Quadrant 2: Business-facing
tests that support the team
4 Quadrant 3: Business-facing
tests that critique the product
4 Quadrant 4: Technology-facing
tests that critique the product

Why Do We Write Unit Tests?
[Revisting]

To find "Bugs" quickly.
What if your "Unit Test" has bugs!

We need processes to help us do things well.
4 Algorithms help you do arithmetic.
4 Test Driven Development (TDD) helps you write
software.
4 Solitary Unit Testing helps you write well designed
software.

Test Driven Development
Red - Green - Refactor
Test-driven development (TDD), is a rapid cycle of testing,
coding, and refactoring.

TDD is Not New!
4 1960: NASA used a similar process in project
Mercury.
4 1994: Simple Smalltalk testing (SUnit)
4 1999: eXtreme Programming by Kent Beck
4 2002: TDD by Example by Kent Beck

TDD Cycle
Red - Green - Refactor
4 Write a failing test for the next bit of functionality.
4 Write the functional code until the test passes.
4 Refactor both new and old code.
TDD is not about "Testing", its more about
"Development".

We rarely have trouble writing code, but they find it
extremely hard to write tests before writing code.
The nature and complexity of code widely affects the ability
to write and run automated tests

Prepare to Experince Awesomeness!
FizzBuzz Kata (TDD)

FizzBuzz
4 Write a program that prints
the numbers from 1 to 100.
4 For multiples of three print
“Fizz” instead of the
number
4 For the multiples of five
print “Buzz”.
4 For numbers which are
multiples of both three and
five print “FizzBuzz”.

Noodle Break, Not
Exactly! Git Help
4 Fork & Getting Started
git clone <url>
cd kata
4 Sync with remote repo
git pull origin master
4 Adding files:
git add .
git commit -m "appropriate message"
git push origin master

"Unit Test" Frameworks
4 To Write Tests: Provides you an
easy way to create & organize
Tests.
4 To Run Tests: Allows you to run
all, or a group of tests or a
single test.
4 Feedback & Intergration:
Immediate "Pass"/"Fail"
feedback.
Examples: MSUnit, JUnit, etc..

Canary Test
Start with a "Canary Test".
Its the simplest test you write to
make sure your good with the
code setup.

TDD: Step 1
Write a "Failing Test"

How to Write Super Awesome
"Unit Tests"
4 Name - 3 Parts
4 Unit Of Work
4 Scenario
4 Expected behaviour
4 Structure - 3 "A"s
4 Arrange
4 Act
4 Assert

Do's & Dont's!
4 Zero logic
4 One assertion per test.
4 DAMP, not DRY
4 Write "Solitary", avoide Social
Tests!
4 Don’t use variables, constants
and complex objects in your
assertions, rather stick with
literals.

TDD: Step 2
Just code enough to "Pass the Test"

How to make a Test
"Green"?
1. Fake It: Return a hard coded
value, replace the hard coded
values with variables; until the
real code exits.
2. make It: Real code
implementation, if it is
immediately obvious.
3. Triangulate: Generalize code,
when there are two or more

Super Simple "Tip"
4 Take Baby Steps:
4 Rule 1: The next step to take
should always be as small as
possible.
4 Rule 2: Read "Rule 1" - Yes,
as small as possible.

Why Baby Steps?
We will produce well-designed,
well-tested, and well-factored
code in small, verifiable baby steps.

TDD: Step 3
Improve the code by "Refactoring".

Oh, Yeah Refactoring
4 No "Logic Changes", Just
moving the code around!
4 Explore performant code
options.
4 Keep watching your "Unit
Tests"
4 Remember "Baby Steps" Rule.

Refactoring is
Important!
The most common way that I hear
to screw up TDD is neglecting the
third step. Refactoring the code
to keep it clean is a key part of
the process, otherwise you just
end up with a messy aggregation
of code fragments.

Its Treasure ..
Treat them as important as
production code because they
allow you to make changes
confidently and correctly,
improving your flexibility and
maintainability over time.

TDD Benefits
For Business
4 Requirement Verification
4 Regression Catching
4 Lower Maintenance Costs

TDD Benefits
For Developers
4 Design First
4 Avoiding Over-Engineering
4 Momentum/ Developer
Velocity
4 Confidence

TDD Pitfalls
4 Coverage as a goal.
4 Not recognising what phase
you’re in.
4 Too many end-to-end tests.
4 Too much noise, not enough
signal.
4 Not listening to the tests.
4 Not tackling slow tests.
4 Leaving broken tests.

"TDD doesn't drive good design. TDD
gives you immediate feedback about
what is likely to be bad design." - Kent
Beck

The basic steps of TDD are easy to
learn, but the mindset takes a while to
sink in.
Until it does, TDD will likely seem clumsy, slow, and
awkward. Give yourself two or three months of full-time
TDD use to adjust.

Coding Dojo
To Become Awsome Developer

Image Credits
4 Dreamworks
4 Martin Flower Bliki
Blogs
4 Martin Flower
4 James Shore

Content Reference
4 Test-Driving JavaScript Applications by Venkat
Subramaniam

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