Creating multiple temporary sites
I think too that the easier way is using simplytest.me, which allows to install more than one module and apply patches. (Click on Advanced options, which at first sight could not seem clickable.)


  


Consider that:


As of July, 2017, simplytest.me runs on Ubuntu and PHP 5.5.12-2ubuntu4.4
Some PHP extensions aren't installed, so some Drupal modules cannot be installed (e.g. the LDAP module)
As of March, 2017, it uses the Composer Manager module, so it can install any Composer requirements a module has
Some distributions, like OpenChurch, fail to install


If you don't need to have a fine control over the environment, simplytest.me is perfect for testing modules and combination of modules. It is surely faster to test modules on simplytest.me than using a virtual machine on your computer. The second option has the pro of allowing you to better control what you install at server level, and it helps if you need to reproduce more accurately the production server you are using.

The site is being ported to Drupal 8. You can see the progress on https://new.simplytest.me/. I am not sure it can be used for extended test of modules.

Reference


The project issue queue