Office 365 subscription for testing

Microsoft Office 365 Developer Program provides free one year Office 365 Enterprise Developer with 25 user licenses that you can use to test Office 365 features. For more information, you may visit this link: https://social.technet.microsoft.com/wiki/contents/articles/37830.office-365-how-to-set-up-a-free-developer-tenant.aspx

Why not get an E3 account for a single license which should be a low enough cost ($240/year) that your business can pay for it?

That way you can access many of the features in Office 365 and get familiar with them before your organization moves to Office 365.