Switch to using tmux-test framework

tests/helpers/tpm.sh

@@ -0,0 +1,18 @@
+check_dir_exists_helper() {
+	local dir_path=$1
+	if [ -d "$dir_path" ]; then
+		return 0
+	else
+		return 1
+	fi
+}
+
+# runs the scripts and asserts it has the correct output and exit code
+script_run_helper() {
+	local script="$1"
+	local expected_output="$2"
+	local expected_exit_code="${3:-0}"
+	"$script" |
+		grep "$expected_output" >/dev/null 2>&1 && # grep -q flag quits the script early
+		[ "${PIPESTATUS[0]}" -eq "$expected_exit_code" ]
+}