The Clean Coder - Robert C. Martin

The Clean Coder
Robert C. Martin
Management / Mentorship
Teams & Projects
Does it Blend?
No such thing as a half of person
Gelled Team
takes time for a team to form
Magical about a gelled team
anticipate each other, cover for each other,
support each other, and deman the best from
each other
Which came first, Team or the Project?
Team should not be formed around availability to
work on a project
Team should be first class decesion
Teams are harder to build than projects
Good books, manuals, api's are great mentors
that can reach lots of people
Working with someone
learning how they work, their tricks, the best
that they know of how to do things
Hard Knocks
learning everything on your own
most developers progress this way
very slow, very hard, not fun
10+ years of experience
lead of multiple projects
coordinate multiple teams
Maintain technical role by reading, studying,
practicing, doing and teaching
Trained, competent and energetic
Learn how to work well in teams and become
team leaders
Knowledgeable about current technology but
typically lack experience w/ many diverse
teach apprentices design principles, design
patterns, disciplines, and rituals
Graduates start here
Closely supervised by journeymen
Need intense pair programing
Ought to last a year
someone who works quickly, but without
rushing, who provides reasonoable
estimates and meets commitments
knows when to say no, but tries hard to say yes
a professional
Convincing People
can't convince people to be crafstmen
can't convince them to accept craftmanship
Acceptance is not so much rational as much
human thing
Make craftsmanship observable
act as a role model
What Bob Martin Uses
Source Control
Open Source tools are usually your best option
Enterprise controls usually suck
use open source throughout work, then check
into enterprise tool at the end of the iteration
2008 switched to GIT
old and vanishing as a coding tool
Great general purpose tool, still not premier for
editing code
Bob uses IntelliJ
Issue Tracking
Start small, grow as needed
Bob is using Pivotal Tracker
Continuous Builds
If the build fails, stop the presses and resolve
the issue
Unit Testing Tools
RSPEC foro Ruby
NUnit for .Net
Midje for Clojure
CppUTest for C(++)
Component Testing Tools
FitNesse (written by Bob)
Green Pepper
based on confluence?
Not worth it
Assumes the problem is code/design
problem is in the details
try to UML the details, and you might as well
code the thing
No great diagramming language today that
solves real problems
Behavioral Professionalism
Do no harm
Don't lookout for yourself, lookout for the project
and the customers
We must not create bugs
Human body is more complex and doctors take
an oath to do no harm
QA Should Find Nothing!
All code should be covered with automated unit
100% code coverage
Why write code and never test that it works
Professionally proves the system works
Delivering function at the expense of structure is
a fool's errand
You must be able to make changes without
exorbitant costs
Merciless refactoring
Make every class you touch slightly better
Always be improving
Difficulty to improve is bad design, fix it
Work Ethic
168 Hours per week
40 hours to solve your employers problems
20 hours on your career
3 hours per day
Lunch hour to read
Podcasts while traveling
56 hours for sleep
52 hours for everything else
Minimal list Software Professional should be
conversant with
Design patterns
all 24 in the GOF book
Design principles
SOLID principles
XP, Scrum, Lean, Kanban, Waterfall, Structured
Analysis and Structured Design
TDD, ObjectOriented design, Structured
Programming, Continuous Integration and Pair
UML, DFDs, Structure Charts, Petri Nets, State
Transition Diagrams and Tables, flow charts and
decision tables
Continuous Learning
Know your domain
Read a couple books on the new topic
Spend some time with the experts and try to
understand their principles and values
Identify with your employer
Saying No
Professionals speak truth to power, and have
the courage to say no to their managers
Being a Team Player
Telling the truth, committing to realistic
estimates and not backing down is best for
Don't allow anyone to lie to try to make the team
sound better, its not beneficial to anyone, the
project, the company or the customer
Admitting you can try harder implies you have
not been trying hard
It applies you and your team to a new
commitment that no one really thinks is
This will inevitably lead to failure and put the
project in a bad spot
Just say no
Don't accept you need to try to meet a date that
is not agreed upon by the team
A professional is already trying, there is no
magic pixie dust to make us work better on
Say no to trying
Response: I could try to levitate, but I promise
you I won't
I could try to change lead in to gold
I could try to swim across the Atlantic
Don't stop by washing your hands and saying no
If your boss is not taking 'no' seriously, make it
clear his/her boss needs to be told the truth, or
you will tell them
This is for the good of the company, not
yourself, not your boss, for everyone, this is
your professional responsibility and right
Saying Yes
Language of Commitment
Making a Commitment
Say you'll do it
Mean it
Actually do it
Most communicated commitments are never real
"Yeah, we really need to get some new routers"
Ask a team members to run tests >"Sure. I hope
to get to it by the end of the day"
But we know we will have to check with him the
next day
Management to the team >"We have to move
Which means the team needs to move faster
but management will not do anything toward
that goal
Recognizing Lack of Commitment
Signs of non commitment
We need to get this done
I need to lose weight
Someone should make that happen
I hope to get this done by tomorrow
I hope we can meet again some day
I wish I had time for that
I wish this computer was faster
"Let's" (not followed by"I")
Let's meet sometime
Let's finish this thing
How to Commit
"I will... by..."
I will finish this by Tuesday
Bad Excuses
It wouldn't work because I rely on person X to
get this done
You can still commit to different parts, and you
should make those apparent and clear
I can sit with Gary for an hour and understand the
I can create an interface that abstracts the
module's dependency
I can meet three times this week w/ the build guy
to make sure your changes work well in the
build system
I can create an integration test for the module
It wouldn't work because I don't really know if it
can be done
You can still commit to actions. Instead to
committing to fixing all 25 remaining bugs for a
I can go through all 25 bugs and try to recreate
I can sit down with the QA who found each bug to
see a repro of that bug
I can spend all the time I have this week trying to
fix each bug
It wouldn't work because sometimes I just won't
make it
Sometimes this is life, but you need to raise a
red flag as soon as possible to whoever you
committed to
Going to be late for a meeting, as soon as you
know, call your colleague and find a solution,
maybe postpone or change locations
You can work to change the commitment in the
best way possible
A task/bug is more difficult than anticipated, tell
the team and come to a conclusion on how to
move forward. Maybe fix specific pieces that
you have discovered.
Don't allow vagueness
Never say or accept you will try to meet a goal
Don't hope for a goal you don't think is a
certainty. Promise what you honestly need for a
This will force an awkward conversation to make
a change. Maybe you reduce features to meet a
desired deadline. Maybe the deadline gets
moved back.
Potentially being responsibly creative to meet a
deadline can be okay, just don't be the only one
I will work 4 hours on Saturday and work with
Willy Monday, but I will take Tuesday off
because I know I will be useless without a
Time Management
Huge Time Wasters
need to use your time wisely
don't accept meetings unless it is a meeting for
which your participation is immediately and
significantly necessary to the job your doing now
You are the only one who can manager your
time, your current project is highest priority, it is
your responsibility to weigh which is more
Your management should help keep you out of
unnecessary meetings
When the meeting gets boring, leave
politely exit that meeting
remaining in a meeting that has become a
waste of time for you and you can no longer
significantly contribute is unprofessional
Have an Agenda and a Goal
When invited, try to get the details of agenda
and how much time is alloted for them
if you can't get this information politely decline
When meeting gets side tracked ask the new
topic be tabled and the agenda be followed
if this doesn't happen you should politely leave
when possible
Data is the best way to argue, not relentless
Run experiments or do some simulation or
Sometimes flipping a coin is best
If one path works out great, otherwise you can go
down the other path
Pick a time frame in which to decide if path's
need to change
Passive aggressive behavior is unprofessional
'This is how he wants it so this is how he will
get it'
If an argument must truly be settled, ask each of
the arguers to present their case to the team in
5 minutes
have the team vote
whole meeting will take less than 15 min
Good nights sleep
Moderate caffeine
long walk
conversation w/ friends
power nap
listen to podcast
Muscle focus
bike riding
building models
Pomodoro Technique
25 minute timer
politely decline all interruptions to get back to
them within 25 min
Priority Inversion
Convincing yourself something else is more
important to avoid doing the real work
Unprofessional Don't do!
Blind Alleys
technical pathways that will lead no where
The Rule of Holes: When you are in one, stop
What Is an Estimate?
Business sees them as Commitment
must achieve
no matter what it takes
Professionals don't commit unless they KNOW
they can achieve the goal
Developers sees them as Guesses
A Guess
no commitment is implied
no promise is made
Professional needs to be careful not to make
any implied commitments with estimates
Missing an estimate is not dishonorable
An Estimate is a probability distribution
most likely will get done at our estimate forced
can get done sooner if things work out
can take much longer, twice, three times as
long if things go poorly
Program Evaluation and Review Technique
Trivariate analysis
O Optimistic Estimate
N Nominal Estimate
P Pessimistic Estimate
Expected duration
Mue= (O + 4N + P)/6
Standard deviation
(P O)/6
O 1
N 3
P 12
Expected: 4.2 days
Standard Deviation: 1.8 days
Sequence Calculations
Sequence expected
Summation of each expected
Sequence deviation
sqrt(sum of squares of deviations)
Wideband Delphi
Team of people assemble, discuss a task,
estimate the task, and iterate the discussion
and estimation until they reach agreement
Flying Fingers
Fingers below table and show on 3, if
agreement or close move on
Planning Poker
see scrum planning poker
Affinity Estimation
Cards with the tasks written on them are silently
ordered by the team from smaller to larger left to
Once most cards settle, discuss disagreements
Assign bucket points to the cards
Trivariate Estimates
Get three estimates, pessimistic, nominal and
Can use any of the three approaches still
Law of large numbers
break up tasks into smaller tasks and estimate
them independently
Don't want your surgeon to stop best practices
while under 'dead'lines
Avoid Pressures
avoid committing to deadlines we can't meet
help the business meet goals set by others but
don't take ownership of the commitment
If we can't find a way to meet the promises
made by the business, then the people who
made the promises must accept the
Stay Clean
"quick and dirty" is an oxymoron
Dirty always means slow
Crisis Discipline
How you behave in crisis shows what you truly
believe in
If you don't do TDD in crisis then you don't truly
believe it's helpful
If you make messes during crunch time, then you
don't truly believe messes slow you down
Choose the methods you feel comfortable
following in a crisis, then follow them all the
Handling Pressure
Don't Panic
Don't stay up all night, sit and frett, or rush,
none of these things will help solve the
Slow down and think the problem through
Let your team and superiors know you are in
Discuss the best plans to get out of trouble, ask
for their input
Avoid creating surprises for anyone
Rely on your disciplines
TDD more
Refactor harder
Get Help
Pair Program!
Coding Professionalism
Your code must work
Never write 3am code: It's crap even if it works,
and that crap will be copied and pasted
Never write code when distracted with personal
Same analogy for driving, driving needs your
focus, don't drive when distracted
Learn how to manage your time with those
problems. Spend some blocks of time
throughout the day working on both to ease
your mind and allow you to code
Avoid the 'zone'
True the zone will allow you to write more code
however that's not an indicator your more
The zone causes tunnel vision and causes you to
lose sight of the big picture
This will cause you to revisit this code a lot which
defeats the purpose of the increase in code
Pair programming makes it near impossible to
enter the zone
Avoid listening to music and headphones this
doesn't usually help you code, it helps you stay
in the zone which is undesired
The zone causes you to be rude to interruptions
extremely unprofessional to be rude
Pairing helps avoid or deal with interruptions to
allow the other to be productive and help you
get back into context after the interruption
TDD helps you stay in context as well, having a
failing test to gain context, this will help with
Writers Block
Pair Program
Reduce debugging time to a minimum
Do this with TDD
Layers constantly retrying cases, surgeons reopening up
patients are unprofessional
constantly having to debug your code is
No False Delivery
Worst unprofessionalism of all
Your code must solve the problem set for you by
the customer
Not the requirements given, it is up to you to
negotiate with the customer the true solution to
their problem
Your code needs to follow solid engineering
Your code must be readable by other
programmers (clean code)
Help Others
your responsibility to be available to help each
unprofessional to sequester yourself in a
cubicle and refuse the queries of others
Your work is not so important that you
cannot lend some of your time to help
If needed set office hours
Offer to help, don't wait to be asked
Accept Help
Mentor junior developers personally
Test Driven Development
It just works!
Surgeons don't have to defend handwashing
Developers don't have to defend TDD
3 Laws
You are not allowed to write any production
code until you have first written a failing unit
You are not allowed to write more of a unit
test than is sufficient to fail and not
compiling is failing.
You are not allowed to write more production
code that is sufficient to pass the currently
failing unit test
tens of unit tests written a day makes me certain
the code works when I wrote it and still works
Defect Injection Rate
Proven to reduce the amount of bugs
Bad code is scary to fix without unit tests so
often it doesn't get fixed
TDD helps give us courage and the confidant
ability to refactor and fix code
When developers lose their fear of cleaning,
they clean
Each unit test defines how the system should
be used
Unit test displays:
how to create every object
every way that object can be created
how to call every function in the system
every way that those functions can
meaningfully be called
Anything you need to know how to do will be a
unit test
Implicit, constantly updating, constantly added
Following the laws forces you to be able to test
your code
This forces you to consider and implement good
design qualities
If tests are written after the code is written, it's
written defensively and will force the
implementation to work
Tests written first are written offensively and will
design the objects in the best way possible so
it's easiest to use, forcing good design
Magic Formula
Does not guarantee the benefits and you can
still write bad code with it
You can even write bad tests
Always be practical or appropriate
professionals should never follow a discipline
when that discipline does more harm than good
a precise set of choreographed movements that
stimulates one side of a combat
Attempt to practice so much to reach perfection
Practicing over and over how to solve a
particular problem
You already know the solution, but practicing the
problem solving motions of TDD is the goal
Drive common problem/solution pairs into your
The Bowling Game
Integer Square Root
Prime Factors
Word Wrap
Twoman kata
Pingpong pair programming pattern
First person writes a failing test
Second person passes it
Second person writes a failing test
First person passes it
When you both really know the kata
Critique each other's keyboarding and
mousing techniques.
Switch it up and add constraints in the tests
speed & memory
Make it competitive and fun
freeform combat
Wasa with more than 2 people
People rotate through while the code is
projected on the wall
Can go in order, people can skip, move
around, etc no specific rules just with more
Broaden Your Experience
Open Source projects
Practice on your own time, its not your
employers responsibility to keep you sharp
Acceptance Testing
Premature Precesion
Business wants to know exactly what they are
going to get, programmers want to know
exactly what they are supposed to deliver
Both want a precision that simply cannot be
Uncertainty principle
requirements when implemented often aren't
really what is desired in the end
observer effect
Estimation anxiety
Late Ambiguity
Testing ALWAYS gets cut first
Rerunning manual tests are very expensive
Having a product that the customer doesn't
want is very expensive for everyone
Automated acceptance testing is cheap
Can maybe appear more expensive/work but
it's the only way to prove it's working and
continues to work
Who writes them?
Ideally stakeholders and QA
realistically business analysts and QA
analysts test happy paths
QA tests unhappy paths
If developers are forced to write them
Should not be the same developer who
implemented it
When to write?
Should be written before the implementation
Midsprint should have all the acceptance
tests written and failing
It is your professional responsibility to
negotiate with whom has written the test and
make a better test when necessary
NEVER be passiveaggressive
X has to run in under 2 seconds
Negotiate on average 2 seconds
"not what requirements say"
realistically though it's the only way
run test 15 times and average is less than 2
NOT unit tests
not redundant
test things very differently
Testing Strategies
Should never find any bugs
But probably still will
Should be a part of the team
Test Automation Pyramid (coverage %)
5% Manual Exploratory
NOT automated, nor scripted
NOT written test plan of this kind of testing
Some teams will have a specialist do this,
others will declare a day or two of 'bug hunting'
to bang on the system
10% System tests
Ultimate integration tests across the entire
NOT test business rules
written by system architects and technical leads
20% integration tests
choreography tests how well the
assembly of components dances
NOT test business rules
Written by system architects or lead designers
of the system
typically not executed as part of CI
Usually apart of nightly/weekly builds
50% component tests
Acceptance tests of specific components
Written by QA and business with assistance
from development
apart of continuous integration suite
100% unit tests
written by programmers for programmers
as close to 100%, generally in the 90s of true
With Employers
First responsibility is to meet the needs of your
understand business goals
collaborate with managers, business analysts,
testers and other team members to understand
understand the business and keep it afloat
With Programmers
owned code
Programmers should never own a piece of code
Collective Ownership
Break down all walls of code ownership and
have the team own the code
Many programmeres dislike the idea
odd because most pair in emergencies
clearly the most efficient way to solve the
two heads are better than one
Professionals Pair
Best way to solve problems
Best way to share knowledge with eachother
Professionals don't create knowledge silos
Best way to review code
Need to be close to team members
need to hear frustrated mutters, serendipitous
Need to communicate as a unit
Some may work better alone for just themselves
but that doesn't mean the team works better
when you work alone
And its unlikely you work better when you work
Probably just work more comfortably