ExpectedSystemExit restores SecurityManager.

After each test the original SecurityManager is restored.

Signed-off-by: Stefan Birkner <mail@stefan-birkner.de>

src/main/java/org/junit/contrib/java/lang/system/ExpectedSystemExit.java

@@ -1,6 +1,5 @@
 package org.junit.contrib.java.lang.system;
 
-import static java.lang.System.setSecurityManager;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
@@ -61,21 +60,21 @@ public void expectSystemExit() {
 		expectExit = true;
 	}
 
-	public Statement apply(final Statement base, final Description description) {
-		return new Statement() {
+	public Statement apply(final Statement base, Description description) {
+		ProvideSecurityManager provideNoExitSecurityManager = new ProvideSecurityManager(
+				new NoExitSecurityManager());
+		Statement statement = new Statement() {
 			@Override
 			public void evaluate() throws Throwable {
-				setSecurityManager(new NoExitSecurityManager());
 				try {
 					base.evaluate();
 					handleMissingSystemExit();
 				} catch (TryToExitException e) {
 					handleSystemExit(e);
-				} finally {
-					setSecurityManager(null);
 				}
 			}
 		};
+		return provideNoExitSecurityManager.apply(statement, description);
 	}
 
 	private void handleMissingSystemExit() {

src/test/java/org/junit/contrib/java/lang/system/ExpectedSystemExitTest.java

@@ -1,10 +1,13 @@
 package org.junit.contrib.java.lang.system;
 
 import static java.lang.System.getSecurityManager;
+import static java.lang.System.setSecurityManager;
 import static org.hamcrest.core.IsSame.sameInstance;
 import static org.junit.Assert.assertThat;
 import static org.junit.rules.ExpectedException.none;
 
+import java.security.Permission;
+
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
@@ -56,7 +59,8 @@ public void failForWrongStatus() throws Throwable {
 
 	@Test
 	public void restoreOldSecurityManager() throws Throwable {
-		SecurityManager manager = getSecurityManager();
+		SecurityManager manager = new ArbitrarySecurityManager();
+		setSecurityManager(manager);
 		executeRuleWithoutExitCall();
 		assertThat(getSecurityManager(), sameInstance(manager));
 	}
@@ -79,4 +83,11 @@ public void evaluate() throws Throwable {
 			System.exit(0);
 		}
 	}
+
+	private static class ArbitrarySecurityManager extends SecurityManager {
+		@Override
+		public void checkPermission(Permission perm) {
+			// allow anything.
+		}
+	}
 }