C#: Add dotnet test that targets dll.

csharp/ql/integration-tests/posix-only/dotnet_test/test.py

@@ -1,5 +1,10 @@
 from create_database_utils import *
 from diagnostics_test_utils import *
 
-run_codeql_database_create(['dotnet test'], db=None, lang="csharp")
+# Implicitly build and then run tests.
+run_codeql_database_create(['dotnet test'], test_db="test-db", lang="csharp")
 check_diagnostics()
+
+# Explicitly build and then run tests.
+run_codeql_database_create(['dotnet clean', 'rm -rf test-db', 'dotnet build -o myout', 'dotnet test myout/dotnet_test.dll'], test_db="test2-db", lang="csharp")
+check_diagnostics(test_db="test2-db")