add basic CTRL interface tests

Prepare for adding tests of enable-/disable-/status-ps CTRL commands.

Change-Id: Ie195169c574716b514da7e04a3ce9727ef70a55e
diff --git a/configure.ac b/configure.ac
index 6532940..167d7f3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -47,6 +47,21 @@
 dnl checks for header files
 AC_HEADER_STDC
 
+AC_ARG_ENABLE([external_tests],
+		AC_HELP_STRING([--enable-external-tests],
+				[Include the VTY/CTRL tests in make check [default=no]]),
+		[enable_ext_tests="$enableval"],[enable_ext_tests="no"])
+if test "x$enable_ext_tests" = "xyes" ; then
+	AM_PATH_PYTHON
+	AC_CHECK_PROG(OSMOTESTEXT_CHECK,osmotestvty.py,yes)
+	 if test "x$OSMOTESTEXT_CHECK" != "xyes" ; then
+		AC_MSG_ERROR([Please install git://osmocom.org/python/osmo-python-tests to run the VTY/CTRL tests.])
+	fi
+fi
+AC_MSG_CHECKING([whether to enable VTY/CTRL tests])
+AC_MSG_RESULT([$enable_ext_tests])
+AM_CONDITIONAL(ENABLE_EXT_TESTS, test "x$enable_ext_tests" = "xyes")
+
 AC_OUTPUT(
 	Makefile
 	src/Makefile