Selenium conf functional programming workshop

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Functional Programming
in
Test Automation
-Narmadha & Sameena
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Narmadha Ramasamy
Senior Consultant @Thoughtworks
linkedin.com/in/narmadha956/
narmadha956@gmail.com
Sameena Syed
Senior Consultant @Thoughtworks
linkedin.com/in/sameena-syed/
sameena9010@gmail.com

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Functional
Programming
Functional Programming is a
programming style where we use Pure
functions extensively
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● Functions as variables
● Functions as arguments
● Functions as return types
First class citizens – FUNCTIONS
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Impure Functions
f(x)
Pure Functions
f(x)
Pure & Impure Functions
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Same input Same output Same input
Output 1
Output 2
……….

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Business Requirement
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Hey Team !
Our app juice shop is ready,
can we have automated tests
to test different workflows

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Functional Programming thinking
 IMPURE FUNCTIONS (Actions)
 PURE FUNCTIONS (Calculations)
 DATA (Data about events, users etc)
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Application Tour
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Business use case
Buy juice items from juice shop
o Given user is logged in
o When cart is empty
o Then user should be able to select juice items and checkout successfully
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We need to ensure checkout of juice items works as expected, as it’s the most sold type of item.

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User Journey
1. Login to application with registered user
2. Get all items in Juice shop portal
3. Add juices to cart
4. Navigate to cart
5. Checkout items in cart
6. Select delivery address
7. Select delivery speed
8. Select payment method
9. Validate cart total and checkout
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CODE Walkthrough
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1. Launch application -> launchApplication()
2. Login to application with registered user -> login()
3. Get all items in Juice shop portal -> getAllItems()
4. Add juices to cart -> getJuiceTypeItems(), addJuicesToCart()
5. Navigate to cart -> navigateToCart()
6. Checkout items in cart -> checkoutCart()
7. Select delivery address -> selectAddress()
8. Select delivery speed -> selectDelivery()
9. Select payment method -> payAndContinue()
10. Validate total price -> assert.equal(totalPriceDisplayed,expectedTotalPrice)
11. Validate order confirmation -> getOrderConfirmation()
Method Mapping

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Business Requirement
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Hey Team !
Looks like we are getting
more data and business
flows, is our existing
automated tests are scalable
???

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 Map : Returns list of same length as input
 Filter : Returns list reduced length as input
 Reduce : Returns single object
Commonly used Higher Order Functions
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CODE Refactoring
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Call Graph
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expectedTotalPrice()
addJuicesToCart()
getJuiceTypeItems()
filter() map() reduce() slice()
getAllItems()
navigateToCart() checkoutCart()
selectDeliverySpeed() getOrderConfirmation()
BUSINESS LAYER
CART OPERATIONS
ITEM OPERATIONS
selectAddress() payAndContinue()
Array-Built Ins

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 Always separate out business rules as functions
 Using call graph to design test case
 Extract calculations from actions as much as possible
 Keep data immutable
 Avoid implicit input & output instead use function arguments & return statements
 Refactor specific names to generic names
 Duplicate code is code smell
Practices to Follow
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New Requirement
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Clients have decided to give
bonus points for cart price
above 999 !
Can we develop this asap

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Currying
How to stop passing the same arguments repeatedly to different functions??
• Use currying
Transformation of a function with multiple arguments to a function with single arg and
returns a function that takes the other args
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CODE Refactoring
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Call Graph
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expectedTotalPrice()
addItemsToCart()
geRequiredItems()
filter() map() reduce() slice()
getAllItems()
navigateToCart() checkoutCart()
calcDeliveryCharges() getOrderConfirmation()
BUSINESS LAYER
CART OPERATIONS
ITEM OPERATIONS
selectAddress() payAndContinue()
Array-Built Ins
calcBonusPoints()

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 Dynamic systems
 Distribution
 Data heavy systems
 Concurrent systems
FP is more suitable for
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Other FP languages
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• Elixir
• Erlang
• Common Lisp
• Haskell
• F#
• Clojure
• Elm
• Racket
• OCaml
• Idris
• PureScript
• Wolfram
• Scala
• Python
• Kotlin
• JavaScript

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● Data immutability affects performance. If
performance takes a hit , then code will have to be
refactored
● Recursion is complex than loop iteration
Disadvantages
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References
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https://www.manning.com/books/grokking-simplicity
https://www.youtube.com/watch?v=BQ-9e13kJ58&t=2035s
https://www.youtube.com/watch?v=sCAR8ZPM6ew
https://dev.to/darkmavis1980/a-practical-example-on-how-to-use-currying-in-javascript-1ae9

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THANK YOU !!