Functional programming is reemerging in popularity but can be difficult for you to use at your day job. At the same time automated browser testing is very practical and has become something that every developer can at least dip their toe in. Canopy, a simple framework in F# on top of Selenium for writing UI automation and tests, can be a great way to start learning a functional language. This talk will explore some of the basic functional concepts targeting those are new to functional programming and show how they can be practically used to automate your browser testing.

1. FUNCTIONAL BROWSER
AUTOMATION TESTING
FOR NEWBS
Bryan Arendt
@ctrlshiftbryan
Canopy F#

2. THIS TALK
Intro Story
Problem
Why Functional Programming & Functional Concepts
Why Functional Stories
F#
Selenium & Why Automated Testing
Canopy

3. THIS TALK
Intro Story
Problem
Why Functional Programming & Functional Concepts
Why Functional Stories
F#
Selenium & Why Automated Testing
Canopy

4. HISTORY OF BRYAN ARENDT
Commodore 64 + Basic (1989)
Guitar (1995)
OSU (1999)
The Sun (2002)
Quit Day Job (2005)
First Heard of F# (2013)
Code Mash (2016)

5. THIS TALK
Intro Story
Problem
Why Functional Programming
Functional Concepts
Why Functional Stories
F#
Selenium & Why Automated Testing
Canopy

6. THE PROBLEM(S)
How do we learn how to be a more
functional programmer(s)?
How do we reduce complexity of
automated browser testing?

7. THIS TALK
Intro Story
Problem
Why Functional Programming & Functional Concepts
Why Functional Stories
F#
Selenium & Why Automated Testing
Canopy

8. WHY FUNCTIONAL?
Readability and maintainability
 A function accomplishes a specific task given its arguments. The function does not
rely on any external state
Easier testing and debugging
 They can be tested in isolation
Reduce Code = Reduce Bugs
Easier reiterative development
 the code is easier to refactor, changes to design are often easier to implement

9. THINKING FUNCTIONALLY
Take parameters Transforms values Returns new values

10. FUNCTIONAL PROGRAMMING
CONCEPTS
Immutability Expressiveness
Types & Values Pure Functions

11. FUNCTIONAL PROGRAMMING
CONCEPTS
Immutability Expressiveness
Types & Values Pure Functions

12. IMMUTABILITY
Values and State cannot be changed once created
Removes side effects
Removes changing state

13. VALUES INSTEAD OF VARIABLES
Instead of changing the value of an existing variable, create a new
variable with the specified initial value.
In functional programming we bind a value to a name.

16. FUNCTIONAL PROGRAMMING
CONCEPTS
Immutability Expressiveness
Types & Values Pure Functions

17. EXAMPLE OF EXPRESSIVENESS
We are going to explore the idea of being terse or expressive.
I’m going to have some help from two people…

18. “There are only two hard things in Computer Science: cache
invalidation and naming things.”
Phil Karlton

19. Function f
Var x

20. UNCLE BOB

21. NAMES
Variable Names
Variables with large scope should be long, and small scope should be
short. Variables scope should be proportional with their length of
names. Variable names like I and j are just fine if their scope is five
lines long.
Function Names
The longer the scope of a function, the shorter its name should be.
Functions that are called locally from a few nearby places should have
long descriptive names, and the longest function names should be
given to those functions that are called from just one place.

23. IN FUNCTIONAL PROGRAMMING
Functions are commonly named f
Variables are commonly named x

24. FUNCTIONAL PROGRAMMING
CONCEPTS
Immutability Expressiveness
Types & Values Pure Functions

25. TYPES & VALUES
Every function is a value
Every value has a type
Entire programs can be type checked for correctness

26. PASSING A FUNCTION TO A
FUNCTION

27. FUNCTIONAL PROGRAMMING
CONCEPTS
Immutability Expressiveness
Types & Values Pure Functions

28. PURE FUNCTIONS: REMOVING SIDE
EFFECTS
Kris Jenkins – What is Functional Programming?
http://blog.jenkster.com/2015/12/what-is-functional-
programming.html
Two types of inputs and outputs

29. NORMAL

30. HIDDEN

31. “SIDE-EFFECTS ARE THE
COMPLEXITY ICEBERG”

32. “SIDE-EFFECTS ARE THE
COMPLEXITY ICEBERG”

33. FUNCTION W/ HIDDEN INPUT

34. PURE FUNCTION

35. REVIEW FUNCTIONAL
PROGRAMMING CONCEPTS
Immutability Expressiveness
Types Pure Functions

36. THIS TALK
Intro Story
Problem
Why Functional Programming & Functional Concepts
Why Functional Stories
F#
Selenium & Why Automated Testing
Canopy

37. WHY FUNCTIONAL – STORY 1
Rachel Reese
http://rachelree.se/rewriting-from-c-into-f/
I rewrote into F# a super simple data transferring app from C#

38. C# -> F#
70% less time! - F# 2 minutes
25% less code! – 140 lines to 103
Bug - processing tremendously more data than needed (F# made this
apparent)
Bug Couple Hours -> 7 Minutes – fixing C#

39. WHY FUNCTIONAL – STORY 2
Does the Language You Use Make a Difference (revisited)?
http://simontylercousins.net/does-the-language-you-use-make-a-
difference-revisited/
Simon Tyler Cousins @simontcousins

40. WHY FUNCTIONAL – STORY 2
Develop an application to evaluate the revenue due from Balancing
Services contracts
Existing solution implemented in C#

41. PROBLEMS
not all of the contracts had been implemented – too complex
hard to maintain the large code base
impossible to test without live data
low confidence in the numbers it produced
failed to evaluate the contracts in near-real-time

42. DESIGN PRINCIPLE
Stay safe, Stay functional.
In particular, we have an immutable domain model and persistence
store. Pure functions are used to work with this domain model.

46. Simon Tyler Cousins @simontcousins

47. HOW CAN WE ALL DO THIS?
How can we convince this guy?

48. THIS TALK
Intro Story
Problem
Why Functional Programming & Functional Concepts
Why Functional Stories
F#
Selenium & Why Automated Testing
Canopy

50. F#
Mostly Functional
Leverage .Net Environment
We can call a compiled C# .Net program or library from F# very easily
Nuget!

51. C# MOST POPULAR FEATURES
Generics / Type parameterization
Lambda Expressions
Delegates
Type Inference (limited)

52. F#
Functional Imperative
Haskel,
OCaml
F# C# C
Multi-paradigmFunctional Imperative

53. MIXED PARADIGM LANGUAGES
If C# is a object oriented language that supports and includes some
functional concepts
F# in the inverse.
Then F# is a functional language that supports object oriented
concepts

54. LOOKING FOR AN EXCUSE TO USE
F#

55. CANOPY - F#RICTIONLESS WEB TESTING
one goal in mind, make UI testing simple:
• Solid stabilization layer built on top of
Selenium.
• Quick to learn. Even if you've never done UI
Automation, and don't know F#.
• Clean, concise API.

56. THIS TALK
Intro Story
Problem
Why Functional Programming & Functional Concepts
Why Functional Stories
F#
Selenium & Why Automated Testing
Canopy

57. WHY AUTOMATED TESTING?
Regression
Test More Like A User (High Level)
Combinatorial Testing
Exact Requirements
Many Browsers

58. WHAT IS SELENIUM?
A Unified API for Browsers
WebDriver
Server/Grid
IDE (For Recording)

59. SELENIUM ARCHITECTURE
Library- [C#][Ruby][Java][Python][...]
 Navigate to a Page
 Send Keystroke
 Click on Elements
 Read Information
WebDriver API Rest Based Web Service
WebDriver Executable
 translates API calls
 each browser has its own web driver
 Chrome and IE each have separate executables
 Firefox and PhantomJS are built-in

60. THIS TALK
Intro Story
Problem
Why Functional Programming & Functional Concepts
Why Functional Stories
F#
Selenium & Why Automated Testing
Canopy

61. CANOPY F#
Canopy F# .Net C# Nuget
WebDriver
REST Api
WebDriver
Executable

62. CANOPY
Actions
Assertions
Testing
Configuration
Reporting

64. OPEN LIBRARIES AND START A
BROWSER

65. DEFINE A TEST

66. THE &&& FUNCTION

67. INFIX FUNCTION
Prefix notation: + 3 4
Infix notation: 3 + 4

69. NO BRACES

70. ASSERTION FUNCTIONS

73. PATTERN MATCHING
Common.fs
Login.fs

75. THIS TALK RECAP
Intro Story
Problem
Why Functional Programming & Functional Concepts
Why Functional Stories
F#
Selenium & Why Automated Testing
Canopy

76. LEARN MORE

77. LEARN MORE
http://fsharpforfunandprofit.com/
http://fsharpforfunandprofit.com/series/low-risk-ways-to-use-
fsharp-at-work.html

78. FUNCTIONAL PROGRAMMING @
CODEMASH
Programs that Write Programs: How Compilers Work
 Thursday 4:45 PM Indigo Bay
Functional Programming Basics in ES6
 Thursday 4:45 PM Zambezi
A Developer’s Journey from Object Oriented to Functional
Programming
 Friday 11:00 AM Zambezi
Erlang, or How I Learned to Stop Worrying and Let Things Fail
 Friday 2:45 PM Orange