Add test

Author: teunbrand

tests/testthat/test-stat-ydensity.R

@@ -3,3 +3,25 @@ test_that("calc_bw() requires at least two values and correct method", {
   expect_silent(calc_bw(1:5, "nrd0"))
   expect_snapshot_error(calc_bw(1:5, "test"))
 })
+
+test_that("`drop = FALSE` preserves groups with 1 observations", {
+  df <- head(data_frame0(
+    x = factor(rep(1:2, each = 4)),
+    y = rep(1:2, 4),
+    g = rep(c("A", "A", "B", 'B'), 2)
+  ), -1)
+
+  p <- ggplot(df, mapping = aes(x, y, fill = g))
+
+  expect_warning(
+    ld <- layer_data(p + geom_violin(drop = TRUE)),
+    "Groups with fewer than two datapoints have been dropped"
+  )
+  expect_equal(length(unique(ld$x)), 3)
+
+  expect_warning(
+    ld <- layer_data(p + geom_violin(drop = FALSE)),
+    "Cannot compute density for groups with fewer than two datapoints"
+  )
+  expect_equal(length(unique(ld$x)), 4)
+})