diff --git a/test/lib/layout-helpers/tmux.test.sh b/test/lib/layout-helpers/tmux.test.sh
new file mode 100755
index 0000000..2803b22
--- /dev/null
+++ b/test/lib/layout-helpers/tmux.test.sh
@@ -0,0 +1,20 @@
+#! /usr/bin/env bash
+source "../../test-helper.sh"
+source "${root}/lib/layout-helpers.sh"
+
+#
+# tmux() tests.
+#
+
+# Passes all arguments to tmuxifier-tmux.
+stub tmuxifier-tmux
+tmux -V
+tmux --help
+tmux new -s dude
+assert_raises "stub_called_with tmuxifier-tmux -V" 0
+assert_raises "stub_called_with tmuxifier-tmux --help" 0
+assert_raises "stub_called_with tmuxifier-tmux new -s dude" 0
+restore tmuxifier-tmux
+
+# End of tests.
+assert_end "tmux()"