Microsoft doesn't own or operated any test centers for any of our exams... we partner with test provider specialists. We need to work with experts in that field to make sure the testing environment is as secure, up to date, and comfortable as possible for you guys; and Microsoft is not in the business of maintaining worldwide real estate and equipment and all everything else involved in being a testing center of excellence... and there is a lot.
For our IT pro and developer MCP exams, our exam delivery partners are Pearson VUE and Prometric. For Office (Microsoft Office Specialist and the new Microsoft Business Certifications), our exam delivery partner is called Certiport. Microsoft exams are offered via these partners--and that means where they have test centers. For the most part, that is worldwide for all of our programs and exams, but there are exceptions--and Office coverage may be different than for MCP exams. For Office, for example, if your country is not listed in the search tool (sorry, Estonia!!), then we unfortunately do not offer testing there. Things change all the time; if you don't find a center that works for you, I recommend contacting the test provider via their support channels to find out if they have plans for your country or if they have an alternative location that might work for you.