When I'm working with a public SPARQL endpoint and get unexpected behaviour, I'm frequently not sure if I'm doing something wrong, or the endpoint is faulty (most of the time it is a somewhat experimental/beta service).
Is there a validator/debugging utility available for SPARQL endpoints, something between vapour and RED. E.g. testing for invalid responses, supported output, nonstandard features, available extensions?
A new tool just became available for checking uptime and status of any SPARQL endpoint listed in the CKAN.
I haven't run into any tools like that, but using the command line web client tool cURL in conjunction with the DAWG test cases and the Berlin Benchmark would give you what you want with a little scripting. URLs for the above references are:
cURL http://curl.haxx.se/
DAWG Test Cases http://www.w3.org/2001/sw/DataAccess/tests/r2
Berling SPARQL Benchmark (BSBM) http://www4.wiwiss.fu-berlin.de/bizer/BerlinSPARQLBenchmark/