Fix JSONTop() == 1 and JSONbot() == 0

The == operator in `is_top` and `is_bot` causes type confusion when
comparing `JSONTop()` and `JSONbot()` values.

Fix it by using identity test instead of equality.

jsonsubschema/_checkers.py

@@ -235,7 +235,7 @@ def __bool__(self):
 
 
 def is_top(obj):
-    return obj == True or obj == {} or isinstance(obj, JSONtop)
+    return obj is True or obj == {} or isinstance(obj, JSONtop)
 
 
 class JSONbot(JSONschema):
@@ -275,7 +275,7 @@ def __bool__(self):
 
 
 def is_bot(obj):
-    return obj == False \
+    return obj is False \
         or (utils.is_dict(obj) and obj.get("not") == {}) \
         or isinstance(obj, JSONbot) \
         or (isinstance(obj, JSONschema) and obj.isUninhabited())

test/test_checkers.py

@@ -0,0 +1,35 @@
+from jsonsubschema._canonicalization import simplify_schema_and_embed_checkers
+from jsonsubschema._checkers import JSONbot, JSONtop, is_bot, is_top
+import unittest
+
+
+class TestIsTop(unittest.TestCase):
+    def test_true_is_top(self) -> None:
+        self.assertTrue(is_top(True))
+
+    def test_empty_object_is_top(self) -> None:
+        self.assertTrue(is_top({}))
+
+    def test_json_top_is_top(self) -> None:
+        self.assertTrue(is_top(JSONtop()))
+
+    def test_one_is_not_top(self) -> None:
+        self.assertFalse(is_top(1))
+
+
+class TestIsBot(unittest.TestCase):
+    def test_false_is_bot(self) -> None:
+        self.assertTrue(is_bot(False))
+
+    def test_not_empty_object_is_bot(self) -> None:
+        self.assertTrue(is_bot({"not": {}}))
+
+    def test_json_bot_is_bot(self) -> None:
+        self.assertTrue(is_bot(JSONbot()))
+
+    def test_uninhabited_schema_is_bot(self) -> None:
+        uninhabited_schema = simplify_schema_and_embed_checkers({"type": "integer", "minimum": 2, "maximum": 1})
+        self.assertTrue(is_bot(uninhabited_schema))
+
+    def test_zero_is_not_bot(self) -> None:
+        self.assertFalse(is_bot(0))