1 files changed, 22 insertions, 0 deletions
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index e5cb08c..1ca3eda 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -4016,6 +4016,28 @@ class CTextIOWrapperTest(TextIOWrapperTest):
         t.write("x"*chunk_size)
         self.assertEqual([b"abcdef", b"ghi", b"x"*chunk_size], buf._write_stack)
 
+    def test_issue119506(self):
+        chunk_size = 8192
+
+        class MockIO(self.MockRawIO):
+            written = False
+            def write(self, data):
+                if not self.written:
+                    self.written = True
+                    t.write("middle")
+                return super().write(data)
+
+        buf = MockIO()
+        t = self.TextIOWrapper(buf)
+        t.write("abc")
+        t.write("def")
+        # writing data which size >= chunk_size cause flushing buffer before write.
+        t.write("g" * chunk_size)
+        t.flush()
+
+        self.assertEqual([b"abcdef", b"middle", b"g"*chunk_size],
+                         buf._write_stack)
+
 
 class PyTextIOWrapperTest(TextIOWrapperTest):
     io = pyio