diff --git a/test/lib/runtime-test.sh b/test/lib/runtime-test.sh
new file mode 100755
index 0000000..a32ac7b
--- /dev/null
+++ b/test/lib/runtime-test.sh
@@ -0,0 +1,23 @@
+#! /usr/bin/env bash
+source "../test-helper.sh"
+
+#
+# runtime.sh tests.
+#
+
+source "../../lib/runtime.sh"
+
+# We assume env.sh has been sourced if $TMUXIFIER_LAYOUT_PATH has been set.
+assert 'echo $TMUXIFIER_LAYOUT_PATH' "${TMUXIFIER}/layouts"
+
+# We ensure $session_root is set to $HOME by default.
+assert 'echo $session_root' "$HOME"
+
+# We assume layout-helpers.sh has been sourced if a few of them are available.
+for helper in new_window split_v split_h select_window select_pane; do
+  assert "type $helper | head -1" "$helper is a function"
+done
+
+
+# End of tests.
+assert_end "runtime.sh"