add renderer test for student performance subject comparison

[AviraL0013]

Renderer Test: Student Performance Subject Comparison

This PR adds a renderer test based on a subject comparison plot from
my Student Performance Analytics Dashboard built with animint2.

Visualization

The test renders a subject comparison bar chart showing mean grades
per subject (Mathematics, Physics, Chemistry, Biology, English, History)
with individual student grade points overlaid. The semester selector
allows filtering by semester.

What the test verifies

• 6 bar rect elements are rendered, one per subject
• Point circles are rendered for individual student grades
• A selector widget is present in the page
• The semester selector has exactly 2 options (Sem1 and Sem2)
• The plot title "Subject Performance Comparison" is rendered in SVG
• All 6 subject names appear as x-axis tick labels

How to run

library(animint2)
library(XML)
setwd("tests/testthat")
source("helper-functions.R")
source("helper-HTML.R")
tests_init()
testthat::test_file("test-renderer-grade-trends.R")

Result

PASS 11 | FAIL 0 | WARN 0 | SKIP 0

Screencast

demo.1.mp4

@tdhock Please review :)

[tdhock]

your code should show interaction, clickID()

in your video please try line by line execution so we can see the web browser before and after clickID()

[tdhock]

you should change expect_true to expect_ something more specific

[AviraL0013]

Hi @tdhock,

Thank you for the review! I have addressed both points:

1. Added clickID("Physics") in test 7 to verify that clicking a subject bar updates the selected subject and circles are still rendered correctly in the browser.

2. Changed expect_true(length(titles) > 0) to expect_equal(length(titles), 1L) in test 5 for a more specific assertion.

All 13 tests pass locally:
PASS 13 | FAIL 0 | WARN 0 | SKIP 0

Screencast will be added shortly.

[tdhock]

thanks, but the video does not work for me in the comment.
why didn’t you upload to vimeo as was requested in the hard test question?

[AviraL0013]

So Sorry about that! There was a voice glitch in the video.
I am re-recording and will upload the correct Vimeo link shortly.

[AviraL0013]

Hi @tdhock,

Please find the screencast here:
https://vimeo.com/1172330910

The video shows:

• install.packages("chromote")
• tests_init() to start the remote controlled browser
• animint2HTML() to render the subject comparison visualization
• Line by line execution with browser visible throughout
• clickID() interaction showing Physics label opacity change from 0.5 to 1 before and after click
• All 13 tests passing with FAIL 0

Thank you for your patience!