Unit Testing rhandsotable R Shiny

I am trying to test rhandsontable in R shiny app with shinytest package. But fail to access table3 and get a following error:

Error in session_makeRequest(self, private, endpoint, data, params, headers) : undefined is not an object (evaluating 'HTMLWidgets.getInstance(table3).hot')

##app.R

library(shiny)
library(rhandsontable)

create_df <-function() {
  df <-  data.frame(matrix(0.0, ncol = 2, nrow = 1))
  return(df)
}

ui <- basicPage(
  navbarPage("App", id="nav",fluid = TRUE,
             tabPanel("Table 1", id="t1",
                      titlePanel("Table 1"),
                      hr(),
                      fluidRow(column(12,
                                      tagList(
                                        tags$h3("Table 1"),
                                        rHandsontableOutput("table1")
                                      )
                      )),
                      fluidRow(column(12,
                                      tagList(
                                        tags$h3("Table 2"),
                                        rHandsontableOutput("table2")
                                      )))
                      ),

             tabPanel("Table 3",id="t3",
                      titlePanel("Table 3"),
                      hr(),
                      fluidRow(column(12,
                                      tagList(
                                        tags$h3("Table 3"),
                                        rHandsontableOutput("table3")
                                      )
                      )))



    )

)

server <- function(input, output, session) {

  v = reactiveValues()


  observe({ input$table1
    if (!is.null(input$table1)) {
      v$table1<- hot_to_r(input$table1)

    } else {
      v$table1<-create_df()
    }
  })

  output$table1 <- renderRHandsontable({
    rhandsontable(v$table1)
  })

  observe({ input$table2
    if (!is.null(input$table2)) {
      v$table2<- hot_to_r(input$table2)

    } else {
      v$table2<-create_df()
    }
  })

  # observeEvent(input$df,{  
  #   v$df2 <- v$df * 2
  # })

  output$table2 <- renderRHandsontable({
    rhandsontable(v$table2)
  })

  observe({ input$table3
    if (!is.null(input$table3)) {
      v$table3<- hot_to_r(input$table3)

    } else {
      v$table3<-create_df()
    }
  })



  output$table3 <- renderRHandsontable({
    rhandsontable(v$table3)
  })



}

shinyApp(ui = ui, server = server)


#shinytest script

library(shinytest)

app <- ShinyDriver$new("path to app")

app$snapshotInit("mytest")


app$snapshot(screenshot = FALSE)


script <- paste0(
  "var $table = HTMLWidgets.getInstance(table3).hot;",
  "$table.setDataAtCell([[0,0,'1'],[0,1,'1']]);"
)


app$executeScript(script)

app$snapshot(screenshot = FALSE)

My expectation of this script is that first two cells in first row will get values of 1 assigned to them, but it does not happen. Please advise how to solve it. Thank you.