feat(spanner): added asserts to test

Author: sagnghos

google-cloud-spanner/src/main/java/com/google/cloud/spanner/DatabaseId.java

@@ -94,7 +94,7 @@ public static DatabaseId of(String project, String instance, String database) {
     return new DatabaseId(new InstanceId(project, instance), database);
   }
 
-  /** Creates a {@code DatabaseId} with "default" project, given instance and database IDs. */
+  /** Creates a {@code DatabaseId} with "default" as project id, given instance and database IDs. */
   public static DatabaseId of(String instance, String database) {
     return new DatabaseId(new InstanceId("default", instance), database);
   }

google-cloud-spanner/src/test/java/com/google/cloud/spanner/SessionClientTests.java

@@ -515,8 +515,10 @@ public void testSessionNamePatterns() {
     // Valid pattern for external host session name
     String externalHost = "instances/default/databases/test-db/sessions/abcd1234";
     try {
-      SessionId.of(host);
-      SessionId.of(externalHost);
+      SessionId hostSession = SessionId.of(host);
+      assertEquals("abcd1234", hostSession.getName());
+      SessionId externalHostSession = SessionId.of(externalHost);
+      assertEquals("abcd1234", externalHostSession.getName());
       // If no exceptions are thrown, the test will pass
     } catch (IllegalArgumentException e) {
       fail("Expected no exception to be thrown, but got: " + e.getMessage());