🔀 Merge pull request #6 from davep/test-check-time-travel-options

Test history's `can_go_forward` and `can_go_backward`

Author: davep

tests/unit/test_history.py

@@ -31,6 +31,13 @@ def test_empty_history_has_no_length() -> None:
     assert len(History()) == 0
 
 
+##############################################################################
+def test_empty_history_has_nowhere_to_go() -> None:
+    """An empty history should not be able to move."""
+    assert History().can_go_backward is False
+    assert History().can_go_forward is False
+
+
 ##############################################################################
 @mark.parametrize("initial", ([1], [1, 2], range(100)))
 def test_pre_populate_history_has_location(initial: Sequence[int]) -> None:
@@ -105,10 +112,13 @@ def test_backward() -> None:
     """We should be able to move backward through history until we can't."""
     history = History[int]([1, 2, 3])
     assert history.current_location == 2
+    assert history.can_go_backward is True
     assert history.backward() is True
     assert history.current_location == 1
+    assert history.can_go_backward is True
     assert history.backward() is True
     assert history.current_location == 0
+    assert history.can_go_backward is False
     assert history.backward() is False
     assert history.current_location == 0
 
@@ -129,11 +139,15 @@ def test_forward() -> None:
     assert history.backward() is True
     assert history.backward() is True
     assert history.backward() is False
+    assert history.can_go_backward is False
     assert history.current_location == 0
+    assert history.can_go_forward is True
     assert history.forward() is True
     assert history.current_location == 1
+    assert history.can_go_forward is True
     assert history.forward() is True
     assert history.current_location == 2
+    assert history.can_go_forward is False
     assert history.forward() is False
     assert history.current_location == 2