In March 2013, the W3C recommended SPARQL 1.1 to retrieve and manipulate decentralized RDF data. Real-world usage requires advanced features of SPARQL 1.1. recommendations As these are not consistently implemented, we propose a test framework named TFT (Tests for Triple stores) to test the interoperability of the SPARQL endpoint of RDF database systems. This framework can execute the W3C's SPARQL 1.1 test suite and also its own tests of interoperability. To help the developers and end-users of RDF databases, we perform daily tests on Jena-Fuseki, Marmotta-KiWistore, 4Store and three other commercial databases. With these tests, we have built a scoring system named SPARQLScore and share our results on the website http://sparqlscore.com.