MINOR: transformValues test improvement (apache#19106)

Follow-up to 295760d. Also check the
set of state stores as suggested in reviews.

Reviewers: Bruno Cadonna <[email protected]>

Author: lucasbru

streams/src/test/java/org/apache/kafka/streams/kstream/internals/KTableTransformValuesTest.java

@@ -62,6 +62,7 @@
 import java.util.Arrays;
 import java.util.List;
 import java.util.Properties;
+import java.util.Set;
 
 import static org.hamcrest.CoreMatchers.equalTo;
 import static org.hamcrest.CoreMatchers.hasItems;
@@ -410,6 +411,8 @@ public void shouldCalculateCorrectOldValuesIfMaterializedEvenIfStateful() {
 
         final KeyValueStore<String, Integer> keyValueStore = driver.getKeyValueStore(QUERYABLE_NAME);
         assertThat(keyValueStore.get("A"), is(3));
+        assertThat(driver.getAllStateStores().keySet(),
+            equalTo(Set.of(QUERYABLE_NAME, "KTABLE-AGGREGATE-STATE-STORE-0000000005")));
     }
 
     @Test
@@ -434,6 +437,8 @@ public void shouldCalculateCorrectOldValuesIfNotStatefulEvenIfNotMaterialized()
         assertThat(output(), equalTo(Arrays.asList(new KeyValueTimestamp<>("A", "1", 5),
                 new KeyValueTimestamp<>("A", "2", 15),
                 new KeyValueTimestamp<>("A", "3", 15))));
+        assertThat(driver.getAllStateStores().keySet(),
+            equalTo(Set.of("inputTopic-STATE-STORE-0000000000", "KTABLE-AGGREGATE-STATE-STORE-0000000005")));
     }
 
     @Test
@@ -460,6 +465,8 @@ public void shouldCalculateCorrectOldValuesIfNotStatefulEvenNotMaterializedNoQue
         assertThat(output(), equalTo(Arrays.asList(new KeyValueTimestamp<>("A", "1", 5),
             new KeyValueTimestamp<>("A", "2", 15),
             new KeyValueTimestamp<>("A", "3", 15))));
+        assertThat(driver.getAllStateStores().keySet(),
+            equalTo(Set.of("inputTopic-STATE-STORE-0000000000", "KTABLE-AGGREGATE-STATE-STORE-0000000005")));
     }
 
     private ArrayList<KeyValueTimestamp<String, String>> output() {