added test for default config

rule-engine/rule-engine-components/src/test/java/org/thingsboard/rule/engine/action/TbSaveToCustomCassandraTableNodeTest.java

@@ -117,6 +117,12 @@ public class TbSaveToCustomCassandraTableNodeTest {
         node.destroy();
     }
 
+    @Test
+    void verifyDefaultConfig() {
+        assertThat(config.getTableName()).isEqualTo("");
+        assertThat(config.getFieldsMapping()).isEqualTo(Map.of("", ""));
+    }
+
     @Test
     void givenCassandraClusterIsMissing_whenInit_thenThrowsException() {
         var configuration = new TbNodeConfiguration(JacksonUtil.valueToTree(config));