fix: add copyright in test and added assert to header

src/test/java/org/eclipse/tractusx/ssi/lib/serialization/jwt/SignedJwtFactoryTest.java

@@ -1,7 +1,30 @@
+/*
+ * ******************************************************************************
+ * Copyright (c) 2021,2024 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Apache License, Version 2.0 which is available at
+ * https://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * *******************************************************************************
+ */
+
 package org.eclipse.tractusx.ssi.lib.serialization.jwt;
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 
+import com.nimbusds.jose.JWSAlgorithm;
 import com.nimbusds.jwt.SignedJWT;
 import java.util.LinkedHashMap;
 import org.eclipse.tractusx.ssi.lib.SsiLibrary;
@@ -42,5 +65,9 @@ void shouldReturnSignedJWT() {
 
     // Then
     assertNotNull(signedJWT);
+    // check jwt is not empty
+    assertNotNull(signedJWT.serialize());
+    // check jwt header
+    assertEquals(JWSAlgorithm.EdDSA, signedJWT.getHeader().getAlgorithm());
   }
 }