Polish Logging and Tests

Removing debug statements which would have prematurely terminated the
stream, changing to AssertJ, and adding another test.

Issue: gh-3743

core/src/main/java/org/springframework/security/access/expression/method/DefaultMethodSecurityExpressionHandler.java

@@ -175,21 +175,12 @@ public class DefaultMethodSecurityExpressionHandler extends
 
 		if (filterTarget instanceof Stream) {
 			final Stream<?> original = (Stream<?>) filterTarget;
-			if (debug) {
-				logger.debug("Filtering stream with " + original.count() + " elements");
-			}
 
-			Stream<?> filtered = original.filter(filterObject -> {
+			return original.filter(filterObject -> {
 				rootObject.setFilterObject(filterObject);
 				return ExpressionUtils.evaluateAsBoolean(filterExpression, ctx);
 			})
 					.onClose(original::close);
-
-			if (debug) {
-				logger.debug("Retaining elements: " + filtered.collect(Collectors.toList()));
-			}
-
-			return filtered;
 		}
 
 		throw new IllegalArgumentException(

core/src/test/java/org/springframework/security/access/expression/method/DefaultMethodSecurityExpressionHandlerTests.java

@@ -15,11 +15,13 @@
  */
 package org.springframework.security.access.expression.method;
 
-import static org.mockito.Mockito.verify;
+import static org.assertj.core.api.Assertions.*;
+
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.*;
 
 import org.aopalliance.intercept.MethodInvocation;
 import org.junit.After;
-import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -85,9 +87,22 @@ public class DefaultMethodSecurityExpressionHandlerTests {
 
 		Object filtered = handler.filter(stream, expression, context);
 
-		Assert.assertTrue("response was wrong type", Stream.class.isAssignableFrom(filtered.getClass()));
+		assertThat(filtered).isInstanceOf(Stream.class);
 		List<String> list = ((Stream<String>) filtered).collect(Collectors.toList());
-		Assert.assertEquals(2, list.size());
-		Assert.assertFalse("contains filtered element", list.contains("2"));
+		assertThat(list).containsExactly("1", "3");
+	}
+
+	@Test
+	public void filterStreamWhenClosedThenUpstreamGetsClosed() {
+		final Stream<?> upstream = mock(Stream.class);
+		doReturn(Stream.<String>empty()).when(upstream).filter(any());
+
+		Expression expression = handler.getExpressionParser().parseExpression("true");
+
+		EvaluationContext context = handler.createEvaluationContext(authentication,
+				methodInvocation);
+
+		((Stream) handler.filter(upstream, expression, context)).close();
+		verify(upstream).close();
 	}
 }