DynamoDb enhanced client: support UpdateExpressions in single-request update

Author: anasatirbasa

services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/update/UpdateExpressionTest.java

@@ -171,6 +171,44 @@ void merge_expression_with_all_action_types() {
         assertThat(result.addActions()).containsExactly(addAction, extraAddAction);
     }
 
+    @Test
+    void isEmpty_emptyExpression_returnsTrue() {
+        UpdateExpression updateExpression = UpdateExpression.builder().build();
+        assertThat(updateExpression.isEmpty()).isTrue();
+    }
+
+    @Test
+    void isEmpty_withRemoveAction_returnsFalse() {
+        UpdateExpression updateExpression = UpdateExpression.builder()
+                                                            .addAction(removeAction)
+                                                            .build();
+        assertThat(updateExpression.isEmpty()).isFalse();
+    }
+
+    @Test
+    void isEmpty_withSetAction_returnsFalse() {
+        UpdateExpression updateExpression = UpdateExpression.builder()
+                                                            .addAction(setAction)
+                                                            .build();
+        assertThat(updateExpression.isEmpty()).isFalse();
+    }
+
+    @Test
+    void isEmpty_withDeleteAction_returnsFalse() {
+        UpdateExpression updateExpression = UpdateExpression.builder()
+                                                            .addAction(deleteAction)
+                                                            .build();
+        assertThat(updateExpression.isEmpty()).isFalse();
+    }
+
+    @Test
+    void isEmpty_withAddAction_returnsFalse() {
+        UpdateExpression updateExpression = UpdateExpression.builder()
+                                                            .addAction(addAction)
+                                                            .build();
+        assertThat(updateExpression.isEmpty()).isFalse();
+    }
+
     private static final class UnknownUpdateAction implements UpdateAction {
 
     }