update test case

Author: Divendra2006

inst/tests/tests.Rraw

@@ -21078,7 +21078,5 @@ test(2307, { capture.output(print(DT, class = TRUE, show.indices = TRUE)); TRUE
 
 # test for enhancing error message of invalid column #6512
 test(2308, {
-  msg <- tryCatch({ .Call("uniq_diff", as.integer(c(1, 2, -1, 4)), 4, FALSE); NULL }, error = function(e) e$message)
-  print(msg) 
-  return(grepl("\\[-1\\]", msg))
-}, TRUE)
+  melt(data.table(A = 1:5, B = 6:10), id.vars = c("A", "-1"))
+}, error = "One or more values in 'id.vars' are invalid")