       assert CustomSet.equal?(actual, expected)
     end
 
+    @tag :pending
     test "union of non-empty sets contains all unique elements" do
       custom_set_1 = CustomSet.new([1, 3])
       custom_set_2 = CustomSet.new([2, 3])

defmodule CustomSetTest do
  use ExUnit.Case

  # @tag :pending
  describe "new" do
    test "returns a CustomSet struct" do
      assert CustomSet.new([]) == %CustomSet{}
    end

    test "removes duplicates in the given enumerable" do
      actual = CustomSet.new([1, 1, 2, 3])
      expected = CustomSet.new([1, 2, 3])

      assert CustomSet.equal?(actual, expected)
    end

    @tag :pending
    test "difference of two non-empty sets is a set of elements that are only in the first set" do
      custom_set_1 = CustomSet.new([3, 2, 1])
      custom_set_2 = CustomSet.new([2, 4])
