feat(tests): sh file for function testing

tests/func.sh

@@ -0,0 +1,21 @@
+func()
+{
+    echo hello
+}
+
+arg_func()
+{
+    echo first argument is "$1"
+}
+
+func_in_func()
+{
+    func
+}
+
+func_one_line() { echo "this is on one line"; }
+
+func
+arg_func "HERE"
+func_in_func
+func_one_line