Can we check shiny applications using testthat and usethis - r

Question

is there a way to check the below applications. This is a sample application to display selected rows. But in general is there a way to acheive this. For example the below code is perfect. Suppose I may some errors in this and I need to check all in once. Can we do that? I have also pasted the error code down
Correct
library(shiny)
library(DT)
ui <- basicPage(
mainPanel(DT::dataTableOutput('mytable')),
textOutput("selected")
)
server <- function(input, output,session) {
mydata <- reactive({mtcars})
output$mytable = DT::renderDataTable(
datatable(mydata())
)
selectedRow <- eventReactive(input$mytable_rows_selected,{
row.names(mtcars)[c(input$mytable_rows_selected)]
})
output$selected <- renderText({
selectedRow()
})
}
runApp(list(ui = ui, server = server))
Wrong/Error code
library(shiny)
library(DT)
ui <- basicPage(
mainPanel(DT::dataTableOutput('mytable')),
textOutput("selected")
)
server <- function(input, output,session) {
mydata <- reactive({mtcars})
output$mytable = DT::renderDataTable(
datatable(mydata())
)
selectedRow <- eventReactive(input$mytable_rows_selected,{
row.names(mtcars)[c(input$[mytable_rows_selected])]
})
output$selected <- renderText({
selectedRow
})
}
runApp(list(ui = ui, server = server))

Answer 1

I use the package shinytest to test my shiny apps. shinytest uses phantomJS to manipulate the app (i.e. simulate button presses etc.)
An entry in testthat/test-shinyapp.R looks something like:
test_that("Shiny template works", {
app <- shinytest::ShinyDriver$new("Path_To_ShinyApp/"))
# plot changes
# first click makes plot
testthat::expect_false(length(grepl("^(data:image/png;base64)",
app$getAllValues()$output$plot1$src)) > 0)
app$setInputs(apply = "click")
testthat::expect_true(length(grepl("^(data:image/png;base64)",
app$getAllValues()$output$plot1$src)) > 0)
testthat::expect_true(grepl("^(data:image/png;base64)",
app$getAllValues()$output$plot1$src))
# are subsequent changes applied?
testthat::expect_identical(app$getAllValues()$input$xVar, "mpg")
testthat::expect_true(
grepl(" mpg cyl", app$getAllValues()$output$summary1))
app$setInputs(xVar = "drat")
app$setInputs(apply = "click")
testthat::expect_true(
grepl(" drat cyl", app$getAllValues()$output$summary1))
# # test for reactive
# shinytest::expectUpdate(app, xVar = "wt", output = "plot1" )
# shinytest::expectUpdate(app, yVar = "drat", output = "plot1" )
# shinytest::expectUpdate(app, xVar = "cyl", output = "summary1" )
# shinytest::expectUpdate(app, yVar = "mpg", output = "summary1" )
# cleanup
app$stop()
unlink(paste0(ws2us(testDir),"_ShinyApp"), recursive = TRUE)
})