renumbering chapters >= 19

24-class-metaprog/sentinel/sentinel_test.py

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+import pickle
+
+import pytest
+
+from sentinel import Sentinel
+
+
+class PlainSentinel(Sentinel):
+    pass
+
+
+class SentinelCustomRepr(Sentinel):
+    repr = '***SentinelRepr***'
+
+
+def test_repr():
+    assert repr(PlainSentinel) == 'PlainSentinel'
+
+
+def test_cannot_instantiate():
+    with pytest.raises(TypeError) as e:
+        PlainSentinel()
+    msg = "'PlainSentinel' is a sentinel and cannot be instantiated"
+    assert msg in str(e.value)
+
+
+def test_custom_repr():
+    assert repr(SentinelCustomRepr) == '***SentinelRepr***'
+
+
+def test_pickle():
+    s = pickle.dumps(SentinelCustomRepr)
+    ps = pickle.loads(s)
+    assert ps is SentinelCustomRepr
+
+
+def test_sentinel_comes_ready_to_use():
+    assert repr(Sentinel) == 'Sentinel'
+    s = pickle.dumps(Sentinel)
+    ps = pickle.loads(s)
+    assert ps is Sentinel