diff --git a/tests/test-extdiff b/tests/test-extdiff
new file mode 100755
--- /dev/null
+++ b/tests/test-extdiff
@@ -0,0 +1,26 @@
+#!/bin/sh
+
+HGRCPATH=$HGTMP/.hgrc; export HGRCPATH
+echo "[extensions]" >> $HGTMP/.hgrc
+echo "extdiff=" >> $HGTMP/.hgrc
+
+hg init a
+cd a
+echo a > a
+hg add
+hg extdiff -o -Nr
+
+echo "[extdiff]" >> $HGTMP/.hgrc
+echo "cmd.falabala=echo" >> $HGTMP/.hgrc
+echo "opts.falabala=diffing" >> $HGTMP/.hgrc
+
+hg falabala
+
+hg help falabala
+
+hg ci -d '0 0' -mtest1
+
+echo b >> a
+hg ci -d '1 0' -mtest2
+
+hg falabala -r 0:1