Add CommandTest class

Author: alexander-yevsyukov

build.gradle

@@ -54,7 +54,7 @@ allprojects {
     apply plugin: 'idea'
 
     group = 'org.spine3'
-    version = '0.5.17-SNAPSHOT'
+    version = '0.5.18-SNAPSHOT'
 }
 
 ext {

testutil/src/main/java/org/spine3/test/CommandTest.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2016, TeamDev Ltd. All rights reserved.
+ *
+ * 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 org.spine3.test;
+
+import com.google.protobuf.Message;
+import org.spine3.base.Command;
+
+/**
+ * An abstract base for nested tests of aggregate specifications.
+ *
+ * @author Alexander Yevsyukov
+ */
+@SuppressWarnings({"ProtectedField" /* we want easier access from test suites */,
+                   "unused", "AbstractClassNeverImplemented" /* is supposed to be used from outside */})
+
+public abstract class CommandTest<C extends Message> {
+
+    protected final TestCommandFactory commandFactory = TestCommandFactory.newInstance(getClass());
+
+    protected C commandMessage;
+
+    protected Command command;
+
+    protected abstract C createCommandMessage();
+
+    protected void createCommand() {
+        commandMessage = createCommandMessage();
+        command = commandFactory.create(commandMessage);
+    }
+}