diff --git a/py/tests/ctm_test.py b/py/tests/ctm_test.py
--- /dev/null
+++ b/py/tests/ctm_test.py
@@ -0,0 +1,86 @@
+#!/usr/bin/python3
+
+import sys
+import pykms
+
+def ctm_to_blob(ctm, card):
+ len=9
+ arr = bytearray(len*8)
+ view = memoryview(arr).cast("I")
+
+ for x in range(len):
+ i, d = divmod(ctm[x], 1)
+ if i < 0:
+ i = -i
+ sign = 1 << 31
+ else:
+ sign = 0
+ view[x * 2 + 0] = int(d * ((2 ** 32) - 1))
+ view[x * 2 + 1] = int(i) | sign
+ #print("%f = %08x.%08x" % (ctm[x], view[x * 2 + 1], view[x * 2 + 0]))
+
+ return pykms.Blob(card, arr);
+
+
+if len(sys.argv) > 1:
+ conn_name = sys.argv[1]
+else:
+ conn_name = ""
+
+card = pykms.Card()
+res = pykms.ResourceManager(card)
+conn = res.reserve_connector(conn_name)
+crtc = res.reserve_crtc(conn)
+mode = conn.get_default_mode()
+
+fb = pykms.DumbFramebuffer(card, mode.hdisplay, mode.vdisplay, "XR24");
+pykms.draw_test_pattern(fb);
+
+crtc.set_mode(conn, fb, mode)
+
+input("press enter to set normal ctm\n")
+
+ctm = [ 1.0, 0.0, 0.0,
+ 0.0, 1.0, 0.0,
+ 0.0, 0.0, 1.0 ]
+
+ctmb = ctm_to_blob(ctm, card)
+
+crtc.set_prop("CTM", ctmb.id)
+
+input("press enter to set new ctm\n")
+
+ctm = [ 0.0, 1.0, 0.0,
+ 0.0, 0.0, 1.0,
+ 1.0, 0.0, 0.0 ]
+
+ctmb = ctm_to_blob(ctm, card)
+
+crtc.set_prop("CTM", ctmb.id)
+
+print("r->b g->r b->g ctm active\n")
+
+input("press enter to set new ctm\n")
+
+ctm = [ 0.0, 0.0, 1.0,
+ 1.0, 0.0, 0.0,
+ 0.0, 1.0, 0.0 ]
+
+ctmb = ctm_to_blob(ctm, card)
+
+crtc.set_prop("CTM", ctmb.id)
+input("r->g g->b b->r ctm active\n")
+
+input("press enter to turn off the crtc\n")
+
+crtc.disable_mode()
+
+input("press enter to enable crtc again\n")
+
+crtc.set_mode(conn, fb, mode)
+
+input("press enter to remove ctm\n")
+
+crtc.set_prop("CTM", 0)
+
+input("press enter to exit\n")