Extract the test into a separate test class

server/src/main/java/io/spine/server/aggregate/Aggregate.java

@@ -349,7 +349,7 @@ final BatchDispatchOutcome apply(List<Event> events, int snapshotTrigger) {
         System.out.println("Batch size: " + events.size());
         uncommittedHistory.startTracking(snapshotTrigger);
         System.out.println("Uncommitted size before: " + uncommittedHistory.events().list().size());
-        var result = play(versionedEvents);
+        var result = play((List<Event>)versionedEvents);
         System.out.println("Batch successful ? " + result.getSuccessful());
         uncommittedHistory.stopTracking();
         System.out.println("Uncommitted size after: " + uncommittedHistory.events().list().size());

server/src/main/java/io/spine/server/aggregate/AggregateTransaction.java

@@ -41,7 +41,7 @@
  *
  * @param <I> the type of aggregate IDs
  * @param <S> the type of aggregate state
- * @param <B> the type of a {@code ValidatingBuilder} for the aggregate state
+ * @param <B> the type of {@code ValidatingBuilder} for the aggregate state
  */
 @Internal
 public class AggregateTransaction<I,

server/src/test/java/io/spine/server/aggregate/AggregateCachingTest.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2022, TeamDev. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Redistribution and use in source and/or binary forms, with or without
+ * modification, must retain the above copyright notice and the following
+ * disclaimer.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package io.spine.server.aggregate;
+
+import io.spine.environment.Tests;
+import io.spine.server.BoundedContextBuilder;
+import io.spine.server.ServerEnvironment;
+import io.spine.server.aggregate.given.salary.Employee;
+import io.spine.server.aggregate.given.salary.EmployeeAgg;
+import io.spine.server.aggregate.given.salary.PreparedInboxStorage;
+import io.spine.server.aggregate.given.salary.PreparedStorageFactory;
+import io.spine.server.delivery.DeliveryStrategy;
+import io.spine.type.TypeUrl;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static com.google.common.truth.Truth.assertThat;
+import static io.spine.server.aggregate.given.aggregate.AggregateTestEnv.command;
+import static io.spine.server.aggregate.given.salary.Employees.decreaseSalary;
+import static io.spine.server.aggregate.given.salary.Employees.employ;
+import static io.spine.server.aggregate.given.salary.Employees.increaseSalary;
+import static io.spine.server.aggregate.given.salary.Employees.newEmployee;
+
+@DisplayName("Cached `Aggregate` should")
+class AggregateCachingTest {
+
+    @Test
+    @DisplayName("store only successfully applied events")
+    void storeEventsOnlyIfApplied() {
+        var jack = newEmployee();
+        var shardIndex = DeliveryStrategy.newIndex(0, 1);
+        var inboxStorage = PreparedInboxStorage.withCommands(
+                shardIndex,
+                TypeUrl.of(Employee.class),
+                command(employ(jack, 250)),
+                command(decreaseSalary(jack, 15)),
+
+                // this one will fail the aggregate's state
+                // as no employee can be paid less than 200.
+                command(decreaseSalary(jack, 500)),
+
+                command(increaseSalary(jack, 500))
+        );
+
+        var serverEnv = ServerEnvironment.instance();
+        serverEnv.reset();
+        ServerEnvironment.when(Tests.class).use(PreparedStorageFactory.with(inboxStorage));
+
+        var repository = new DefaultAggregateRepository<>(EmployeeAgg.class);
+        BoundedContextBuilder.assumingTests()
+                             .add(repository)
+                             .build();
+
+        serverEnv.delivery().deliverMessagesFrom(shardIndex);
+        serverEnv.reset();
+
+        var storedEvents = repository.aggregateStorage()
+                                     .read(jack)
+                                     .orElseThrow()
+                                     .getEventList();
+        assertThat(storedEvents.size()).isEqualTo(3);
+    }
+}

server/src/test/java/io/spine/server/aggregate/AggregateTest.java

@@ -457,42 +457,6 @@ void restoreSnapshot() {
         assertEquals(aggregate, anotherAggregate);
     }
 
-    @Test
-    @DisplayName("store events only if they were successfully applied")
-    void storeEventsOnlyIfApplied() {
-        var jack = newEmployee();
-        var shardIndex = DeliveryStrategy.newIndex(0, 1);
-        var inboxStorage = PreparedInboxStorage.withCommands(
-                shardIndex,
-                TypeUrl.of(Employee.class),
-                command(employ(jack, 250)),
-                command(decreaseSalary(jack, 15)),
-                command(decreaseSalary(jack, 500)),
-                command(increaseSalary(jack, 500))
-        );
-
-        var serverEnv = ServerEnvironment.instance();
-        serverEnv.reset();
-        ServerEnvironment.when(Tests.class).use(PreparedStorageFactory.with(inboxStorage));
-
-        var repository = new DefaultAggregateRepository<>(EmployeeAgg.class);
-        BoundedContextBuilder.assumingTests()
-                             .add(repository)
-                             .build();
-
-        serverEnv.delivery().deliverMessagesFrom(shardIndex);
-        serverEnv.reset();
-
-        var storedEvents = repository.aggregateStorage()
-                                     .read(jack)
-                                     .orElseThrow()
-                                     .getEventList();
-        var singleEvent = storedEvents.get(0).enclosedMessage();
-
-        assertThat(storedEvents.size()).isEqualTo(1);
-        assertThat(singleEvent.getClass()).isEqualTo(NewEmployed.class);
-    }
-
     @Nested
     @DisplayName("after dispatch, return event records")
     class ReturnEventRecords {