In your scenario I would recommend preparing a deployment environment with the evaluation version of Windows that allows you to image the new systems quickly with your test environment.
For example on your server or workstation you could install the
Microsoft Deployment Toolkit (MDT) and then import the Windows 8.1 Enterprise Evaluation from the
TechNet Evaluation Center. Depending on the test environment you are looking to implement, you could use MDT to install your test software or create a custom image with the software installed. You could then create USB installation media that would install this image on each new computer.
Some notes worth considering:
• If you create a custom image, you will want to use a virtual machine for the reference system. A virtual machine with minimal drivers is the surest way to ensure maximum compatibility with various hardware configurations.
• Your installation media can include the image, a.k.a. offline media, or can be a minimal environment that installs the image over the network.
• If you import your applications into MDT rather than creating a custom image, the installation process can be granular. You can be prompted with a list of applications to install each time and pick and choose the ones you need.
• While the deployment will include all of the drivers of a native installation out of the box, you may need to import specific drivers into MDT to enable certain devices on the resulting computer. You could also just install those drivers manually on the computer after deployment. While this is an extra step, it addresses the possibility of the environment crashing or refusing to work on each new computer.