fixed SpotBugs JUA_DONT_ASSERT_INSTANCEOF_IN_TESTS

core/src/test/java/jenkins/util/xstream/XStreamDOMTest.java

@@ -25,11 +25,13 @@ package jenkins.util.xstream;
 
 import hudson.util.XStream2;
 import org.apache.commons.io.IOUtils;
+import org.hamcrest.core.IsInstanceOf;
 import org.junit.Before;
 import org.junit.Test;
 import org.xmlunit.diff.DefaultNodeMatcher;
 import org.xmlunit.diff.ElementSelectors;
 
+import static org.hamcrest.Matchers.instanceOf;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
 import static org.hamcrest.MatcherAssert.assertThat;
@@ -141,7 +143,7 @@ public class XStreamDOMTest {
         v.values.put("foo",createSomeFoo().bar);
         String xml = xs.toXML(v);
         Object v2 = xs.fromXML(xml);
-        assertTrue(v2 instanceof DomInMap);
+        assertThat(v2, instanceOf(DomInMap.class));
         assertXStreamDOMEquals(v.values.get("foo"), ((DomInMap)v2).values.get("foo"));
     }