python-msgpack: add test script

Add a CI test.sh exercising basic package functionality.

Signed-off-by: Alexandru Ardelean <alex@shruggie.ro>

lang/python/python-msgpack/test.sh

@@ -0,0 +1,18 @@
+#!/bin/sh
+
+[ "$1" = python3-msgpack ] || exit 0
+
+python3 - << 'EOF'
+
+import msgpack
+
+# Pack a mixed-type structure and unpack it back, then confirm the compiled C
+# extension is actually in use rather than the pure-Python fallback (which the
+# package silently drops to when the Cython build produced nothing).
+obj = {"a": [1, 2, 3], "b": "text", "c": 3.5, "d": True, "e": None}
+packed = msgpack.packb(obj)
+assert isinstance(packed, (bytes, bytearray))
+assert msgpack.unpackb(packed, raw=False) == obj
+assert msgpack.Packer.__module__ == "msgpack._cmsgpack", msgpack.Packer.__module__
+
+EOF