Setting ArcGIS Desktop license to lower level for testing whether Python script still runs?

If this will be a recurring effort where you need to test your products at various license levels, it might be worth purchasing an Esri Developer Network license.

Esri Developer Network (EDN) is available through an annual subscription and provides a cost-effective way to license Esri ArcGIS products and tools. Whether you're a Web, desktop, mobile, or server developer, EDN has the resources you need for building GIS applications and solutions.