add test

Author: Kirill Müller

inst/tests/test-layer.r

@@ -0,0 +1,7 @@
+context("Layer")
+
+test_that("Correctly decide if a variable is a calculated aesthetic", {
+  expect_true(ggplot2:::is_calculated_aes(aes(x=..density..)))
+  expect_false(ggplot2:::is_calculated_aes(aes(x=a..x..b)))
+  expect_equal(as.character(ggplot2:::strip_dots(aes(x=..density..))), "density")
+})