use snapshot test

Author: teunbrand

tests/testthat/_snaps/geom-raster.md

@@ -14,6 +14,14 @@
 
     `vjust` must be a number, not the string "a".
 
+---
+
+    Code
+      b <- ggplotGrob(p)
+    Message
+      `geom_raster()` only works with linear coordinate systems, not `coord_polar()`.
+      i Falling back to drawing as `geom_rect()`.
+
 # geom_raster() fails with pattern fills
 
     Problem while converting geom to grob.

tests/testthat/test-geom-raster.R

@@ -6,7 +6,7 @@ test_that("geom_raster() checks input and coordinate system", {
 
   df <- data_frame(x = rep(c(-1, 1), each = 3), y = rep(-1:1, 2), z = 1:6)
   p <- ggplot(df, aes(x, y, fill = z)) + geom_raster() + coord_polar()
-  expect_message(ggplotGrob(p), "only works with")
+  expect_snapshot(b <- ggplotGrob(p))
 })
 
 test_that("geom_raster() fails with pattern fills", {