Fixes pytest

Author: sobolevn

docs/pages/concept.rst

@@ -87,7 +87,7 @@ Let's define some instances:
 
 .. code:: python
 
-  >>> @json.instance  # You can use just the annotation
+  >>> @json.instance(str)
   ... def _json_str(instance: str) -> str:
   ...     return '"{0}"'.format(instance)
 

setup.cfg

@@ -80,6 +80,13 @@ omit =
   # which does not work with coverage:
   classes/contrib/mypy/*
 
+[coverage:report]
+exclude_lines =
+  # a more strict default pragma
+  \# pragma: no cover\b
+
+  ^if TYPE_CHECKING:
+
 
 [mypy]
 # mypy configurations: http://bit.ly/2zEl9WI

tests/test_typeclass/test_reuse.py

@@ -0,0 +1,26 @@
+import pytest
+
+from classes import typeclass
+
+
+class _Example(object):
+    def __call__(self, instance) -> str:
+        """Example class-based typeclass def."""
+
+
+def _example(instance) -> str:
+    """Example function-based typeclass def."""
+
+
+def test_class_reuse() -> None:
+    """Ensures that it is impossible to reuse classes."""
+    typeclass(_Example)
+
+    with pytest.raises(TypeError):
+        typeclass(_Example)
+
+
+def test_function_reuse() -> None:
+    """Ensures that it is possible to reuse classes."""
+    typeclass(_example)
+    typeclass(_example)