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#' Reactive testing for Shiny server functions and modules
#'
#' A way to test the reactive interactions in Shiny applications. Reactive
#' interactions are defined in the server function of applications and in
#' modules.
#' @param app A server function (i.e. a function with `input`, `output`,
#' and `session`), or a module function (i.e. a function with first
#' argument `id` that calls [moduleServer()].
#'
#' You can also provide an app, a path an app, or anything that
#' [`as.shiny.appobj()`] can handle.
#' @param expr Test code containing expectations. The objects from inside the
#' server function environment will be made available in the environment of
#' the test expression (this is done using a data mask with
#' [rlang::eval_tidy()]). This includes the parameters of the server function
#' (e.g. `input`, `output`, and `session`), along with any other values
#' created inside of the server function.
#' @param args Additional arguments to pass to the module function. If `app` is
#' a module, and no `id` argument is provided, one will be generated and
#' supplied automatically.
#' @param session The [`MockShinySession`] object to use as the [reactive
#' domain][shiny::domains]. The same session object is used as the domain both
#' during invocation of the server or module under test and during evaluation
#' of `expr`.
#' @include mock-session.R
#' @rdname testServer
#' @examples
#' # Testing a server function ----------------------------------------------
#' server <- function(input, output, session) {
#' x <- reactive(input$a * input$b)
#' }
#'
#' testServer(server, {
#' session$setInputs(a = 2, b = 3)
#' stopifnot(x() == 6)
#' })
#'
#'
#' # Testing a module --------------------------------------------------------
#' myModuleServer <- function(id, multiplier = 2, prefix = "I am ") {
#' moduleServer(id, function(input, output, session) {
#' myreactive <- reactive({
#' input$x * multiplier
#' })
#' output$txt <- renderText({
#' paste0(prefix, myreactive())
#' })
#' })
#' }
#'
#' testServer(myModuleServer, args = list(multiplier = 2), {
#' session$setInputs(x = 1)
#' # You're also free to use third-party
#' # testing packages like testthat:
#' # expect_equal(myreactive(), 2)
#' stopifnot(myreactive() == 2)
#' stopifnot(output$txt == "I am 2")
#'
#' session$setInputs(x = 2)
#' stopifnot(myreactive() == 4)
#' stopifnot(output$txt == "I am 4")
#' # Any additional arguments, below, are passed along to the module.
#' })
#' @export
testServer <- function(app = NULL, expr, args = list(), session = MockShinySession$new()) {
require(shiny)
if (!is.null(getDefaultReactiveDomain()))
stop("testServer() is for use only within tests and may not indirectly call itself.")
on.exit(if (!session$isClosed()) session$close(), add = TRUE)
quosure <- rlang::enquo(expr)
if (isModuleServer(app)) {
if (!("id" %in% names(args)))
args[["id"]] <- session$genId()
# app is presumed to be a module, and modules may take additional arguments,
# so splice in any args.
withMockContext(session, rlang::exec(app, !!!args))
# If app is a module, then we must use both the module function's immediate
# environment and also its enclosing environment to construct the mask.
parent_clone <- rlang::env_clone(parent.env(session$env))
clone <- rlang::env_clone(session$env, parent_clone)
mask <- rlang::new_data_mask(clone, parent_clone)
withMockContext(session, rlang::eval_tidy(quosure, mask, rlang::caller_env()))
return(invisible())
}
if (is.null(app)) {
path <- findEnclosingApp(".")
app <- shinyAppDir(path)
} else if (isServer(app)) {
app <- shinyApp(fluidPage(), app)
} else {
app <- as.shiny.appobj(app)
}
if (!is.null(app$onStart))
app$onStart()
if (!is.null(app$onStop))
on.exit(app$onStop(), add = TRUE)
server <- app$serverFuncSource()
if (!"session" %in% names(formals(server)))
stop("Tested application server functions must declare input, output, and session arguments.")
if (length(args))
stop("Arguments were provided to a server function.")
body(server) <- rlang::expr({
session$setEnv(base::environment())
!!body(server)
})
withMockContext(session,
server(input = session$input, output = session$output, session = session)
)
# # If app is a server, we use only the server function's immediate
# # environment to construct the mask.
mask <- rlang::new_data_mask(rlang::env_clone(session$env))
withMockContext(session, {
rlang::eval_tidy(quosure, mask, rlang::caller_env())
})
invisible()
}
withMockContext <- function(session, expr) {
isolate(
withReactiveDomain(session, {
withr::with_options(list(`shiny.allowoutputreads` = TRUE), {
# Sets a cache for renderCachedPlot() with cache = "app" to use.
shinyOptions("cache" = session$appcache)
expr
})
})
)
}
# Helpers -----------------------------------------------------------------
isModuleServer <- function(x) {
is.function(x) && names(formals(x))[[1]] == "id"
}
isServer <- function(x) {
if (!is.function(x)) {
return(FALSE)
}
if (length(formals(x)) < 3) {
return(FALSE)
}
identical(names(formals(x))[1:3], c("input", "output", "session"))
}
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