Add a test for rstudio/shiny#2593

Author: cpsievert

172-showcase-filenames/DESCRIPTION

@@ -0,0 +1,7 @@
+Title: Hello Shiny!
+Author: RStudio, Inc.
+AuthorUrl: http://www.rstudio.com/
+License: MIT
+DisplayMode: Showcase
+Tags: getting-started
+Type: Shiny

172-showcase-filenames/My Script.R

@@ -0,0 +1,11 @@
+msg <- tagList(
+  p(
+    "Opening this app in showcase mode should,",
+    "show code from the testapp.R file (on initial load)."
+  ),
+  p("Also, you should be able to click to view 'My Script.R'"),
+  p(
+    "PR:", a("#2593", href = "https://github.com/rstudio/shiny/pull/2593"),
+    "Issue: ", a("#1926", href = "https://github.com/rstudio/shiny/issues/1926")
+  )
+)

172-showcase-filenames/testapp.R

@@ -0,0 +1,12 @@
+library(shiny)
+library(plotly)
+
+source("My Script.R")
+
+ui <- fluidPage(uiOutput("msg"))
+
+server <- function(input, output, session) {
+  output$msg <- renderUI(msg)
+}
+
+shinyApp(ui, server, options = list(display.mode = "showcase"))