add test for message on unknown implementation

Author: simonpcouch

tests/testthat/_snaps/misc.md

@@ -0,0 +1,16 @@
+# model type functions message informatively with unknown implementation
+
+    Code
+      bag_tree() %>% set_engine("rpart")
+    Message
+      parsnip could not locate an implementation for `bag_tree`  model specifications using the `rpart` engine.
+    Output
+      Bagged Decision Tree Model Specification (unknown)
+      
+      Main Arguments:
+        cost_complexity = 0
+        min_n = 2
+      
+      Computational engine: rpart 
+      
+

tests/testthat/test_misc.R

@@ -98,3 +98,11 @@ test_that('correct mtry', {
 
 })
 
+# ----------------------------------------------------------------------------
+
+test_that('model type functions message informatively with unknown implementation', {
+  expect_snapshot(
+    bag_tree() %>%
+      set_engine("rpart")
+  )
+})