add snapshot test

Author: teunbrand

tests/testthat/_snaps/scale-.md

@@ -20,6 +20,14 @@
 
     The `scale_name` argument of `binned_scale()` is deprecated as of ggplot2 3.5.0.
 
+# mismatch between `na.value` and `palette` throws error
+
+    Code
+      sc$map(x)
+    Condition
+      Error in `vec_assign()`:
+      ! Can't convert `na.value` <double> to match type of `palette` <character>.
+
 # continuous scales warn about faulty `limits`
 
     Code

tests/testthat/test-scale-.R

@@ -138,6 +138,16 @@ test_that("Using `scale_name` prompts deprecation message", {
 
 })
 
+test_that("mismatch between `na.value` and `palette` throws error", {
+  x <- c("A", "B", "C", NA)
+  sc <- scale_shape_manual(
+    values = c("circle", "triangle", "square"),
+    na.value = 4
+  )
+  sc$train(x)
+  expect_snapshot(sc$map(x), error = TRUE)
+})
+
 # Continuous scales -------------------------------------------------------
 
 test_that("limits with NA are replaced with the min/max of the data for continuous scales", {