     assert List.delete_at([1, 2, 3], -4) == [1, 2, 3]
   end
 
-  test "to string" do
+  test "to_string/1" do
     assert List.to_string([?æ, ?ß]) == "æß"
     assert List.to_string([?a, ?b, ?c]) == "abc"
 

    assert List.replace_at([1, 2, 3], -4, 0) == [1, 2, 3]
  end

  test "update at" do
    assert List.update_at([1, 2, 3], 0, &(&1 + 1)) == [2, 2, 3]
    assert List.update_at([1, 2, 3], 1, &(&1 + 1)) == [1, 3, 3]
    assert List.update_at([1, 2, 3], 2, &(&1 + 1)) == [1, 2, 4]

    assert List.insert_at([1, 2, 3], -10, 0) == [0, 1, 2, 3]
  end

  test "replace_at/3" do
    assert List.replace_at([1, 2, 3], 0, 0) == [0, 2, 3]
    assert List.replace_at([1, 2, 3], 1, 0) == [1, 0, 3]
    assert List.replace_at([1, 2, 3], 2, 0) == [1, 2, 0]
