From fec4742fc0e6a067638ad9078019f165072d4c9c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bogumi=C5=82=20Kami=C5=84ski?= <bkamins@sgh.waw.pl>
Date: Sat, 21 Oct 2023 16:51:52 +0200
Subject: [PATCH] improve test coverage

---
 test/grouping.jl | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/test/grouping.jl b/test/grouping.jl
index df9e79bd3..a1283c656 100644
--- a/test/grouping.jl
+++ b/test/grouping.jl
@@ -4531,4 +4531,9 @@ end
     end
 end
 
+@testset "no levels in pooled grouping bug #3393" begin
+    @test isempty(groupby_checked(DataFrame(x=PooledArray([missing])), :x, skipmissing=true))
+    @test isempty(groupby_checked(DataFrame(x=categorical([missing])), :x, skipmissing=true))
+end
+
 end # module