Test ulist

This demonstrates that ulist has the following issues and needs to be
fixed or removed:

- ulist cannot be instantiated (literally, ulist() raises a TypeError)
- ulist does not guarantee ordering (ulist([3]) + ulist([1, 2]) == [1, 2, 3])
- ulist does not guarantee uniqueness (ulist([1]).extend([1]) is equivalent to [1, 1])

I intend to investigate whether Python sets can be used in place of the
ulist class.

.coveragerc

@@ -13,7 +13,7 @@ source =
 
 [report]
 skip_covered = True
-fail_under = 33
+fail_under = 35
 exclude_lines =
     pragma: no cover
     if __name__ == '__main__':

test/test_ulist.py

@@ -0,0 +1,104 @@
+import pytest
+
+import smartcard.ulist
+
+
+def test_demonstrate_ulist_cannot_be_instantiated():
+    """ulist() cannot be instantiated without an argument."""
+
+    with pytest.raises(TypeError, match="'NoneType' object is not iterable"):
+        smartcard.ulist.ulist()
+
+
+@pytest.mark.xfail(reason="order should be ['x', 1, 2] not [1, 2, 'x']", strict=True)
+def test_demonstrate_order_is_not_respected():
+    """Order is not strictly respected."""
+
+    instance = smartcard.ulist.ulist([1, 2])
+    new_instance = ["x"] + instance
+    assert new_instance == ["x", 1, 2]
+
+
+@pytest.mark.xfail(reason="not all list methods are overwritten", strict=True)
+def test_demonstrate_non_unique_behavior():
+    """ulist.extend() breaks uniqueness guarantees."""
+
+    instance = smartcard.ulist.ulist([1, 2])
+    instance.extend([1, 2, 3])
+    assert instance == [1, 2]  # actually, it's [1, 2, 1, 2, 3]
+
+
+def test_ulist_methods():
+    """This broadly tests the ulist implementation.
+
+    It can be removed when ulist is removed.
+    """
+
+    smartcard.ulist.ulist([])
+    smartcard.ulist.ulist([1])
+    smartcard.ulist.ulist([1, 1])
+    instance = smartcard.ulist.ulist([1])
+    original_id = id(instance)
+    assert instance
+    assert len(instance) == 1
+    assert instance == [1]
+    assert id(instance) == original_id
+
+    instance.append(1)
+    assert instance
+    assert len(instance) == 1
+    assert instance == [1]
+    assert id(instance) == original_id
+
+    instance.append(2)
+    assert instance
+    assert len(instance) == 2
+    assert instance == [1, 2]
+    assert id(instance) == original_id
+
+    new_instance = instance + [3]
+    assert new_instance is not instance
+    assert new_instance == [1, 2, 3]
+    assert instance == [1, 2]
+    assert id(instance) == original_id
+
+    new_instance = instance + [1, 2]
+    assert new_instance is not instance
+    assert new_instance == [1, 2]
+    assert instance == [1, 2]
+    assert id(instance) == original_id
+
+    new_instance = [1, 2] + instance
+    assert new_instance is not instance
+    assert new_instance == [1, 2]
+    assert instance == [1, 2]
+    assert id(instance) == original_id
+
+    instance += 2
+    assert instance == [1, 2]
+    assert id(instance) == original_id
+
+    instance.insert(0, 0)
+    assert len(instance) == 3
+    assert instance == [0, 1, 2]
+
+    instance.insert(10_000, 0)
+    assert len(instance) == 3
+    assert instance == [0, 1, 2]
+
+    value = instance.pop()
+    assert value == 2
+    assert instance == [0, 1]
+    value = instance.pop(0)
+    assert value == 0
+    assert instance == [1]
+    instance.pop()
+
+    instance.append(0)
+    instance.remove(0)
+    with pytest.raises(ValueError):
+        instance.remove(0)
+
+    my_pristine_list = [0, 1, 2, 0, 1, 2, 0, 1, 2]
+    instance += my_pristine_list
+    assert my_pristine_list == [0, 1, 2, 0, 1, 2, 0, 1, 2]