app$expect_values( ) Error in `app_httr_get()` Could not find Shiny server. Shiny app is no longer running

Hi, Thank you for the amazing package, I'm encountering a strange error. When I record a test app, I click on Expect Shiny Values, works great but then when I hit Save test and exit, I get the following Error:

Error in `app_httr_get()` at shinytest2/R/app-driver-expect-values.R:171:2:
! Could not find Shiny server. Shiny app is no longer running

I tried to reproduce the test in code (see below please), I get the same error.

testthat::test_that("testing table outputs in dt_editable module", {
  
  app <- shinytest2::AppDriver$new(
    app_dir = file_path,
    variant = shinytest2::platform_variant(), 
    name = "dt_editable_dev"
  )

 # The following works fine
  app$wait_for_idle(duration = 1000)
  mpg_table <- app$get_html("#mpg_data-editable_dt")
  mtcars_table <- app$get_html("#mtcars_data-editable_dt")
  first_row_in_app <- app$get_text(
    selector = "#mtcars_data-editable_dt tr:first-child td"
  ) 

 # The error comes from this line of code
 app$expect_values(output = "mpg_data-editable_dt")
})

When I try to view( ) the app, I get the following error: 

Fontconfig warning: "/etc/fonts/fonts.conf", line 86: unknown element "blank" [11926:11926:0726/155925.132116:ERROR:ozone_platform_x11.cc(247)] Missing X server or $DISPLAY [11926:11926:0726/155925.132160:ERROR:env.cc(226)] The platform failed to initialize. Exiting.

Maybe it's related the error in the subject but then why the get_url( ) works well :/

Thanks again for the great work :) 


─ Session info ───────────────────────────────────
 setting  value
 version  R version 3.6.0 (2019-04-26)
 os       CentOS Linux 7 (Core)
 system   x86_64, linux-gnu
 ui       RStudio
 language (EN)
 collate  en_US.UTF-8
 ctype    en_US.UTF-8
 tz       Europe/Berlin
 date     2022-07-26
 rstudio  2022.02.1+461.pro1 Prairie Trillium (server)
 pandoc   NA