Remove test for Connection #finalize

This hurts bad to do, and I'm open to any suggestion for how to
do this test in a way that is deterministic.

Whenever #finalize is called on a user-level Session object,
we check that the session was properly closed. If it was not
closed, we generate an error and close the session.

The test for this would create a Session object with no references,
and then run tens of thousands of iterations of System.gc(),
testing for #close() being invoked. This seems to have worked
deterministically on Java 8, but on Java 7 it is flaky.

I don't think testing for Java 7 in a JUnit assumption is
a good solution, and instead I'm opting for removing the test,
with the argument that this has been manually verified to work,
it is a best-effort piece of code that in production usage is
allowed to fail (since we can never guarante the finalizer will
invoke us).

If we drop java 7 support, we could look at reverting this commit.

Author: jakewins

driver/src/main/java/org/neo4j/driver/internal/InternalSession.java

@@ -139,6 +139,7 @@ protected void finalize() throws Throwable
                           "method on Sessions before disposing of the objects.", null );
             connection.close();
         }
+        super.finalize();
     }
 
     private void ensureNoOpenTransaction()

driver/src/test/java/org/neo4j/driver/internal/InternalSessionTest.java

@@ -22,21 +22,13 @@
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
-import java.util.Map;
-import java.util.concurrent.atomic.AtomicBoolean;
-
 import org.neo4j.driver.internal.logging.DevNullLogger;
 import org.neo4j.driver.internal.spi.Connection;
-import org.neo4j.driver.internal.spi.Logger;
-import org.neo4j.driver.internal.spi.StreamCollector;
 import org.neo4j.driver.v1.Transaction;
-import org.neo4j.driver.v1.Value;
 import org.neo4j.driver.v1.exceptions.ClientException;
 
 import static junit.framework.TestCase.assertNotNull;
-import static org.jsoup.helper.Validate.fail;
 import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
@@ -143,81 +135,4 @@ public void shouldNotAllowMoreTransactionsInSessionWhileConnectionClosed() throw
         // When
         sess.beginTransaction();
     }
-
-    @Test
-    public void shouldWarnAndCloseOnLeak() throws Throwable
-    {
-        // Given
-        CloseTrackingConnection connection = new CloseTrackingConnection();
-        Logger logger = spy( Logger.class );
-
-        // When
-        new InternalSession( connection, logger );
-
-        // Then
-        long deadline = System.currentTimeMillis() + 1000 * 30;
-        while ( !connection.closeCalled.get() )
-        {
-            System.gc();
-            if ( System.currentTimeMillis() > deadline )
-            {
-                fail( "Expected unclosed session object to close its inner connection on finalize." );
-            }
-        }
-
-        verify( logger ).error( "Neo4j Session object leaked, please ensure that your application calls the `close` method on Sessions before disposing of the objects.", null );
-    }
-
-    private static class CloseTrackingConnection implements Connection
-    {
-        AtomicBoolean closeCalled = new AtomicBoolean();
-
-        @Override
-        public void init( String clientName )
-        {
-
-        }
-
-        @Override
-        public void run( String statement, Map<String,Value> parameters, StreamCollector collector )
-        {
-
-        }
-
-        @Override
-        public void discardAll()
-        {
-
-        }
-
-        @Override
-        public void pullAll( StreamCollector collector )
-        {
-
-        }
-
-        @Override
-        public void reset( StreamCollector collector )
-        {
-
-        }
-
-        @Override
-        public void sync()
-        {
-
-        }
-
-        @Override
-        public void close()
-        {
-            closeCalled.set( true );
-        }
-
-        @Override
-        public boolean isOpen()
-        {
-            return true;
-        }
-    }
 }