Add alpha test for geom_ribbon

Author: cpsievert

tests/testthat/test-ggplot-ribbon.R

@@ -14,3 +14,13 @@ test_that("sanity check for geom_ribbon", {
 })
 
 save_outputs(rb, "ribbon")
+
+rb2 <- ggplot(huron, aes(x=year)) + 
+  geom_ribbon(aes(ymin=level-1, ymax=level+1), alpha = 0.1)
+L2 <- gg2list(rb2)
+
+test_that("geom_ribbon respects alpha transparency", {
+  expect_true(grepl("0.1\\)$", L2[[1]]$fillcolor))
+})
+
+save_outputs(rb2, "ribbon-alpha")