Using shinytest2 with R packages

For R packages that have Shiny applications, there are generally two ways that the applications will be present in the package. The first is to have an app.R in a subdirectory of inst/. The second way is to have a function which returns a Shiny app object.

Applications in `inst/`

An application could live in a subdirectory of inst/, as shown below:

/
├── DESCRIPTION
├── NAMESPACE
├── R
├── inst
│   └── sample_app
│       ├── app.R
│       └── tests
│           ├── testthat
│           │   ├── _snaps
│           │   │   └── shinytest2
│           │   │       └── 001.json
│           │   └── test-shinytest2.R
│           └── testthat.R
└── tests
    ├── testthat
    │   └── test-inst-apps.R
    └── testthat.R

In this case, you can run record_test() and test_app() as normal. After you create and run the tests, there will be a tests/ subdirectory in the application directory that stores the test scripts and results.

Since we are using {testthat} for automated tests, you would create a test driver script in tests/testthat/. In this example, it’s named test-inst-apps.R and contains the following:

# File: tests/testthat/test-inst-apps.R
library(shinytest2)

test_that("sample_app works", {
  # Don't run these tests on the CRAN build servers
  skip_on_cran()

  appdir <- system.file(package = "exPackage", "sample_app")
  test_app(appdir)
})

If the application directory is not meant to be public, it can also be located in ./tests/testthat/apps. {shinytest2} does this with many application and has appdir above point to the relative path to the application.

Application objects created by functions

The second way have an application in an R package is by having a function that returns a Shiny application object. In this example, there’s a function hello_world_app(), which lives in R/hello-world.R:

/
├── .Rbuildignore
├── DESCRIPTION
├── NAMESPACE
├── R
│   └── hello-world.R
└── tests
    ├── testthat
    │   ├── _snaps
    │   │   └── app-function
    │   │       └── 001.json
    │   └── test-app-function.R
    └── testthat.R

The function simply returns an object from shinyApp():

# File: R/hello-world.R

hello_world_app <- function() {
  utils::data(cars)
  shinyApp(
    ui = fluidPage(
      sliderInput("n", "n", 1, nrow(cars), 10),
      plotOutput("plot")
    ),
    server = function(input, output) {
      output$plot <- renderPlot({
        plot(head(cars, input$n), xlim = range(cars[[1]]), ylim = range(cars[[2]]))
      })
    }
  )
}

Once we have the object, it can be supplied directly to AppDriver$new().

# File: tests/testthat/test-app-function.R

test_that("hello-world app initial values are consistent", {
  # Don't run these tests on the CRAN build servers
  skip_on_cran()

  shiny_app <- hello_world_app()
  app <- AppDriver$new(shiny_app, name = "hello")
  app$expect_values()
})

To help create tests, you can call record_test() on your shiny application object directly. Unfortunately, the test file will not be able to be saved. Instead, the test commands can be copied into a test script manually.

Other setup steps

There are a few steps that are needed for both types of tests.

It is recommended to call shinytest2::use_shinytest() to enable different test config set-ups.

You will need to add {shinytest2} to the Suggests section in your DESCRIPTION file.

Suggests:
    shinytest2

When all of these items are in place, you can test your package using devtools::install(); testthat::test_local() or by running R CMD check on your package. If you are using the RStudio IDE, you can also run Build -> Test Package or Build -> Check Package.

{shinytest2} requires that your package to be installed when testing. testthat::test_local() (and related wrappers) eventually call pkgload::load_all() to temporarily source the local R package. You can use test_local() to test non-{shinytest2} tests, but you will need to install your R package to safely execute your {shinytest2} tests. If not installed, it will create a confusing situation where your {shinytest2} tests are running on a different version of your R package (whichever was last installed), than the rest of your tests (the current source).

Using shinytest2 with R packages

Applications in inst/

Application objects created by functions

Other setup steps

Continuous integration

Applications in `inst/`