Sync custom-set (#1516)

exercises/practice/custom-set/.meta/tests.toml

@@ -114,6 +114,9 @@ description = "Difference (or Complement) of a set is a set of all elements that
 [c5ac673e-d707-4db5-8d69-7082c3a5437e]
 description = "Difference (or Complement) of a set is a set of all elements that are only in the first set -> difference of two non-empty sets is a set of elements that are only in the first set"
 
+[20d0a38f-7bb7-4c4a-ac15-90c7392ecf2b]
+description = "Difference (or Complement) of a set is a set of all elements that are only in the first set -> difference removes all duplicates in the first set"
+
 [c45aed16-5494-455a-9033-5d4c93589dc6]
 description = "Union returns a set of all elements in either set -> union of empty sets is an empty set"
 

exercises/practice/custom-set/test/custom_set_test.exs

@@ -289,6 +289,15 @@ defmodule CustomSetTest do
       expected = CustomSet.new([1, 3])
       assert CustomSet.equal?(actual, expected)
     end
+
+    @tag :pending
+    test "difference removes all duplicates in the first set" do
+      custom_set_1 = CustomSet.new([1, 1])
+      custom_set_2 = CustomSet.new([1])
+      actual = CustomSet.difference(custom_set_1, custom_set_2)
+      expected = CustomSet.new([])
+      assert CustomSet.equal?(actual, expected)
+    end
   end
 
   describe "union" do