explicitly specify the assemblies to test, as AppVeyor test autodetection will detect SparkCLRSamples.exe but fail to find any testfixtures

appveyor.yml

@@ -7,6 +7,10 @@ build_script:
   - cmd: SET JAVA_OPTS=-XX:MaxPermSize=2g -Xmx4g
   - cmd: Build.cmd
 
+test:
+  assemblies:
+    - csharp\AdapterTest\bin\Debug\AdapterTest.dll
+
 # scripts to run after tests
 after_test:
   - cmd: Runsamples.cmd --validate