test(io): share readonly readinto test setup and cases

Author: emerardd

Lib/test/test_io/test_bufferedio.py

@@ -314,20 +314,9 @@ def test_readinto(self):
         self.assertEqual(bufio.readinto(b), 1)
         self.assertEqual(b, b"cb")
 
-    @support.subTests("method", ("readinto", "readinto1"))
-    @support.subTests("buffer", (
-        b"xxx", memoryview(b"xxx"),
-    ))
-    @support.subTests("position", (0, 4))
-    @support.subTests("buffered", (False, True))
-    def test_readinto_readonly_buffer(self, method, buffer, position, buffered):
-        data = b"abcdef"
-        with self.tp(self.BytesIO(data)) as bufio:
-            bufio.seek(position)
-            if buffered:
-                bufio.peek(1)
-            check_readinto_readonly_buffer(
-                self, bufio, method, buffer, position, data[position:])
+    def test_readinto_readonly_buffer(self):
+        check_readinto_readonly_buffer(
+            self, lambda data: self.tp(self.BytesIO(data)), prefill=True)
 
     def test_readinto1(self):
         buffer_size = 10

Lib/test/test_io/test_memoryio.py

@@ -569,17 +569,8 @@ def test_readinto(self):
         memio.readinto(b)
         self.assertEqual(b, b"")
 
-    @support.subTests("method", ("readinto", "readinto1"))
-    @support.subTests("buffer", (
-        b"xxx", memoryview(b"xxx"), b"", memoryview(b""),
-    ))
-    @support.subTests("position", (0, 4, 10))
-    def test_readinto_readonly_buffer(self, method, buffer, position):
-        data = b"abcdef"
-        with self.ioclass(data) as memio:
-            memio.seek(position)
-            check_readinto_readonly_buffer(
-                self, memio, method, buffer, position, data[position:])
+    def test_readinto_readonly_buffer(self):
+        check_readinto_readonly_buffer(self, self.ioclass, empty_and_eof=True)
 
     def test_relative_seek(self):
         buf = self.buftype("1234567890")

Lib/test/test_io/utils.py

@@ -2,6 +2,7 @@
 import threading
 import time
 import unittest
+from itertools import product
 
 import io  # C implementation of io
 import _pyio as pyio # Python implementation of io
@@ -26,12 +27,28 @@ def byteslike(*pos, **kw):
         return obj
 
 
-def check_readinto_readonly_buffer(testcase, stream, method, buffer,
-                                  position, remaining):
-    op = getattr(stream, method)
-    testcase.assertRaises(TypeError, op, buffer)
-    testcase.assertEqual(stream.tell(), position)
-    testcase.assertEqual(stream.read(), remaining)
+def check_readinto_readonly_buffer(testcase, stream_factory, *,
+                                  empty_and_eof=False, prefill=False):
+    data = b"abcdef"
+    buffers = [b"xxx", memoryview(b"xxx")]
+    positions = [0, 4]
+    if empty_and_eof:
+        buffers.extend([b"", memoryview(b"")])
+        positions.append(10)
+    methods = ("readinto", "readinto1")
+    prefilled = (False, True) if prefill else (False,)
+    for method, buffer, position, buffered in product(
+            methods, buffers, positions, prefilled):
+        with testcase.subTest(method=method, buffer=buffer, position=position,
+                              buffered=buffered):
+            with stream_factory(data) as stream:
+                stream.seek(position)
+                if buffered:
+                    stream.peek(1)
+                op = getattr(stream, method)
+                testcase.assertRaises(TypeError, op, buffer)
+                testcase.assertEqual(stream.tell(), position)
+                testcase.assertEqual(stream.read(), data[position:])
 
 
 class MockRawIOWithoutRead: