diff --git a/tests/io/bytesio_ext.py b/tests/io/bytesio_ext.py
new file mode 100644
index 0000000000..30d79fcfcd
--- /dev/null
+++ b/tests/io/bytesio_ext.py
@@ -0,0 +1,19 @@
+# Extended stream operations on io.BytesIO
+try:
+    import uio as io
+except ImportError:
+    import io
+
+a = io.BytesIO()
+print(a.seek(8))
+a.write(b"123")
+print(a.getvalue())
+
+print(a.seek(0, 1))
+
+print(a.seek(-1, 2))
+a.write(b"0")
+print(a.getvalue())
+
+a.flush()
+print(a.getvalue())