Add tests

Author: srittau

Lib/test/test_io.py

@@ -4916,6 +4916,24 @@ class PySignalsTest(SignalsTest):
     test_reentrant_write_text = None
 
 
+class ProtocolsTest(unittest.TestCase):
+    class MyReader:
+        def read(self, sz=-1):
+            return b""
+
+    class MyWriter:
+        def write(self, b: bytes):
+            pass
+
+    def test_reader_subclass(self):
+        self.assertIsSubclass(MyReader, io.Reader[bytes])
+        self.assertNotIsSubclass(str, io.Reader[bytes])
+
+    def test_writer_subclass(self):
+        self.assertIsSubclass(MyWriter, io.Writer[bytes])
+        self.assertNotIsSubclass(str, io.Writer[bytes])
+
+
 def load_tests(loader, tests, pattern):
     tests = (CIOTest, PyIOTest, APIMismatchTest,
              CBufferedReaderTest, PyBufferedReaderTest,

Lib/test/test_typing.py

@@ -4302,6 +4302,40 @@ def __release_buffer__(self, mv: memoryview) -> None:
         self.assertNotIsSubclass(C, ReleasableBuffer)
         self.assertNotIsInstance(C(), ReleasableBuffer)
 
+    def test_io_reader_protocol_allowed(self):
+        @runtime_checkable
+        class CustomReader(io.Reader[bytes], Protocol):
+            def close(self): ...
+
+        class A: pass
+        class B:
+            def read(self, sz=-1):
+                return b""
+            def close(self):
+                pass
+
+        self.assertIsSubclass(B, CustomReader)
+        self.assertIsInstance(B(), CustomReader)
+        self.assertNotIsSubclass(A, CustomReader)
+        self.assertNotIsInstance(A(), CustomReader)
+
+    def test_io_writer_protocol_allowed(self):
+        @runtime_checkable
+        class CustomWriter(io.Writer[bytes], Protocol):
+            def close(self): ...
+
+        class A: pass
+        class B:
+            def write(self, b):
+                pass
+            def close(self):
+                pass
+
+        self.assertIsSubclass(B, CustomWriter)
+        self.assertIsInstance(B(), CustomWriter)
+        self.assertNotIsSubclass(A, CustomWriter)
+        self.assertNotIsInstance(A(), CustomWriter)
+
     def test_builtin_protocol_allowlist(self):
         with self.assertRaises(TypeError):
             class CustomProtocol(TestCase, Protocol):