included unit test for warnings if mapping or data is supplied

Author: thiyangt

tests/testthat/test-stats-function.r

@@ -48,14 +48,10 @@ test_that("works with formula syntax", {
   expect_equal(ret$y, s^2)
 })
 
-test_that("can control whether to preserve total or individual width", {
-  df <- data_frame(x = c("a", "b", "b"), y = c("a", "a", "b"))
-
-  p_total <- ggplot(df, aes(x, fill = y)) +
-    geom_bar(position = position_dodge(preserve = "total"), width = 1)
-  p_single <- ggplot(df, aes(x, fill = y)) +
-    geom_bar(position = position_dodge(preserve = "single"), width = 1)
+test_that("`mapping` is not used by stat_function()", {
+  expect_warning(stat_function(aes(), fun = identity), "Ignoring `mapping`")
+})
 
-  expect_equal(layer_data(p_total)$x, c(1, 2.25, 1.75))
-  expect_equal(layer_data(p_single)$x, c(0.75, 2.25, 1.75))
+test_that("`data` is not used by stat_function()", {
+  expect_warning(stat_function(aes(), fun = identity), "Ignoring `data`")
 })