add --enable-tests flag to ensure dependencies for the tests

Makefile.am

@@ -1,7 +1,8 @@
 ACLOCAL_AMFLAGS = -I m4
 AM_DISTCHECK_CONFIGURE_FLAGS = \
   --without-systemdsystemunitdir \
-  --enable-strict-locations
+  --enable-strict-locations \
+  --enable-tests
 
 EXTRA_DIST = \
   COPYING \

configure.ac

@@ -65,6 +65,10 @@ if test "x$with_systemdsystemunitdir" != xno; then
 fi
 AM_CONDITIONAL(HAVE_SYSTEMD, [test -n "$with_systemdsystemunitdir" -a "x$with_systemdsystemunitdir" != xno ])
 
+AC_ARG_ENABLE(tests,
+              AC_HELP_STRING([--enable-tests],
+              [Ensure dependencies for the tests are installed]),
+              [ensure_tests_deps=yes], [])
 AC_ARG_ENABLE(pam, AS_HELP_STRING([--enable-pam],
               [Build PAM support (default: yes)]),
               [], [enable_pam=yes])
@@ -358,9 +362,15 @@ AC_CHECK_HEADER([X11/extensions/Xrandr.h], [],
 CFLAGS="$save_CFLAGS"
 
 # perform unit tests if libcheck found
-PKG_CHECK_MODULES([CHECK], [check >= 0.10.0],
-    [perform_unit_tests=yes],
-    [perform_unit_tests=no])
+if test "x$ensure_tests_deps" == "xyes"; then
+    PKG_CHECK_MODULES([CHECK], [check >= 0.10.0],
+        [perform_unit_tests=yes],
+        [AC_MSG_ERROR([please install check, the unit test framework])])
+else
+    PKG_CHECK_MODULES([CHECK], [check >= 0.10.0],
+        [perform_unit_tests=yes],
+        [perform_unit_tests=no])
+fi
 
 if test "x$perform_unit_tests" == "xyes"; then
     AC_MSG_NOTICE([libcheck found, unit tests will be performed])
@@ -454,7 +464,7 @@ echo "  libdir                  $libdir"
 echo "  bindir                  $bindir"
 echo "  sysconfdir              $sysconfdir"
 echo ""
-echo "  perform unit tests      $perform_unit_tests"
+echo "  unit tests performable  $perform_unit_tests"
 echo ""
 echo "  CFLAGS = $CFLAGS"
 echo "  LDFLAGS = $LDFLAGS"