Be The Best With Shinytest

Chris CampbellSenior Consultant

ccampbell@mango-solutions.com

@CSJCampbell

Be The Best With Shinytest

Web Development

Shiny

Testing

Shinytest

Web Development

Two Roles for Data Scientists

• Analyst • Developer

Analyst

• design and build workflow – asking a question– gathering data– generating insight– guiding decision making

• investigate impact of assumptions and determine value of workflow

• use existing tools and develop new tools

Developer

• design algorithms that are independent of data

• identify desirable behaviours of algorithm, recognise edge cases

• abstract algorithm into conceptual units• create and document code• test units to demonstrate expected

behaviour• maintain code as software dependencies

and needs of business change

More Roles

• Analyst • Web Developer

• Developer

Web Developer

• wireframe/layout a web application• write HTML and CSS• turn a design into a working website• add interactivity to a website with JavaScript or

jQuery• write an application in an object-oriented

programming language (Ruby, Python or PHP)• work with a version control system like Git• manage a domain’s DNS settings• deploy a website to a website hosthttps://teamtreehouse.com/community/the-list-of-minimum-skills-you-need-to-master-to-call-yourself-a-web-developer

Shiny

Shiny

• Massively popular web application framework

• Winston Chang, Joe Cheng, ...

Web Developer

• wireframe/layout a web application• write HTML and CSS• turn a design into a working website• add interactivity to a website with JavaScript or

jQuery• write an application in an object-oriented

programming language (Ruby, Python or PHP)• work with a version control system like Git• manage a domain’s DNS settings• deploy a website to a website host

Web Developer

• shiny• shiny• shiny• shiny• write an application in R

• work with a version control system like Git• manage a domain’s DNS settings• deploy a website to a website host

Soon Every R Conference Presentation will be about Shiny

Testing

Testing

• Define expected output• Compare object with expected• Fast and fun

Testing Vital for Effective Development• Find defects• Manage impact of new features• Manage impact of changes to

dependencies

Testing Essential for Validation

• Demonstrate features are present• Qualify operation of installed application

Quick to Check Tests Pass

> library(testthat)> test_package("mangoNCA") test AUCInfObs: ......... test AUCInfPred: ......... test AUCLast: ....................test AUCLin: .............. test AUCLog: ................

Clear Failures

Failed --------------------------

1. Failure: check selectPoints(@test_selectPoints.R#25) --------

test3$lamznpt not equal to 4.

1/1 mismatches [1]

3 - 4 == -1

Shinytest

Shinytest

• R-based testing framework for Shiny• Gabor Csardi

Shinytest

Shinytest

• Snapshot based testing• Record– script of test actions– app state

• Replay and compare

Not yet on CRAN

library(devtools)

install_github("rstudio/webdriver")

install_github("rstudio/shinytest")

Create New Test

• Start recording• Interact with Shiny app• Take snapshots

Start Recording

> recordTest("Quiz")

Interact with Shiny app

• Click through app

Take Snapshot

• Recorder app

• Snapshot and continue or exit

Script of Test Actions

app <- ShinyDriver$new("..")

app$snapshotInit("mytest")

app$setInputs(

q1 = "reg = read.csv('Temp/reg.csv')")

app$setInputs(button = "click")

app$snapshot()

Test Directory Created in App

• Test script• App data• Screenshot

Running Tests

• Test driver process• Shiny server process• Web browser client process

Quick to Check Tests Pass

testApp("Quiz", "mytest")

Running mytest.R

====== Comparing mytest ======

Clear Failures

testApp("Quiz", "mytest")Running mytest.R====== Comparing mytest ======Differences detected between

mytest-current/ and mytest-expected/:

Name Status 001.json != Files differ001.png != Files differ

Shinytest

• Automated testing framework for Shiny apps

• All necessary tools installable from R• Outputs can be used with other test

frameworks• Best development practice makes the

best web apps

References

• https://github.com/rstudio/shinytest• https://rstudio.github.io/shinytest/• https://www.mango-

solutions.com/datascience/products/valid-r/