Write up more extensive (and more robust) testing

[Paulj1989]

Problem

Code coverage is currently at just below 50%, which is definitely less than ideal! There is a lot of functionality in the app that isn't being tested, and because there are a lot of dependent elements in the app, this could easily lead to small changes making big problems.

Proposed Solution

The code coverage needs to be, at a minimum, over 80%. There needs to be robust testing in place to make sure the data is pulling through as expected, that the app looks as expected when it loads, that typical usage produces consistent results, and that downloaded plots and data are generated correctly.

Additional Context

R packages and Shiny testing overview:

• R Packages: Testing
• Engineering Production-Grade Shiny Apps: Testing Your App
• Shiny Testing Overview

For basic testing of outputs and business logic in the app:

• {testthat}
• {vdiffr}
• {waldo}

For testing Shiny:

• {shinytest}
• {shinytest2}
• {shinyloadtest}
• {reactor}