Repository: iluwatar/java-design-patterns
Issue: Subclass Sandbox pattern
Labels: epic: pattern
type: feature

http://gameprogrammingpatterns.com/subclass-sandbox.html

Issue comments:
Hello @iluwatar I would like to take this pattern. Thanks!
Ok @szokekristof 
@szokekristof  are you still implementing this?
The task is free to take
@iluwatar May I pick up this issue?
Sure go ahead @Azureyjt 

Pull request review comments:
New dependencies should be introduced in parent pom.xml, and then referenced in submodule. See for example the junit dependency above.
You can use Java's local variable type inference (var) in code like this. Please check it elsewhere too.
typo there
typo there
Fixed in commit 87c55b338aa0e32b9e736c708e0a1b562ca576a0
Fixed in commit 87c55b338aa0e32b9e736c708e0a1b562ca576a0
Fixed in eca54c4460b3683c8e65f68409ef6e158bf53b61
Fixed in a627f17a72df44cf99d83a41fb261c93911d20cd

@iluwatar  Thanks for your suggestion. Since I do not have much experience on using var, could you kindly review my change again to see if it is ok? Thanks. 

Patch that resolved the issue:
diff --git a/pom.xml b/pom.xml
index 9e61e716b864..36d501a92054 100644
--- a/pom.xml
+++ b/pom.xml
@@ -61,6 +61,7 @@
         <jaxb-api.version>2.3.1</jaxb-api.version>
         <jaxb-impl.version>2.3.2</jaxb-impl.version>
         <annotation-api.version>1.3.2</annotation-api.version>
+        <system-rules.version>1.19.0</system-rules.version>
     </properties>
     <modules>
         <module>abstract-factory</module>
@@ -181,8 +182,8 @@
         <module>bytecode</module>
         <module>leader-election</module>
         <module>data-locality</module>
+        <module>subclass-sandbox</module>
         <module>circuit-breaker</module>
-
     </modules>
 
     <repositories>
@@ -323,6 +324,12 @@
                 <artifactId>javassist</artifactId>
                 <version>3.25.0-GA</version>
             </dependency>
+            <dependency>
+                <groupId>com.github.stefanbirkner</groupId>
+                <artifactId>system-rules</artifactId>
+                <version>${system-rules.version}</version>
+                <scope>test</scope>
+            </dependency>
         </dependencies>
     </dependencyManagement>
 
diff --git a/subclass-sandbox/README.md b/subclass-sandbox/README.md
new file mode 100644
index 000000000000..674991f0895c
--- /dev/null
+++ b/subclass-sandbox/README.md
@@ -0,0 +1,29 @@
+
+---  
+layout: pattern  
+title: Subclass Sandbox 
+folder:  subclass-sandbox  
+permalink: /patterns/subclass-sandbox/  
+categories: Other  
+tags:  
+ - Java  
+ - Difficulty-Beginner  
+---  
+  
+## Intent  
+The subclass sandbox pattern describes a basic idea, while not having a lot of detailed mechanics. You will need the pattern when you have several similar subclasses. If you have to make a tiny change, then change the base class, while all subclasses shouldn't have to be touched. So the base class has to be able to provide all of the operations a derived class needs to perform.
+  
+## Applicability  
+The Subclass Sandbox pattern is a very simple, common pattern lurking in lots of codebases, even outside of games. If you have a non-virtual protected method laying around, you’re probably already using something like this. Subclass Sandbox is a good fit when:
+
+-   You have a base class with a number of derived classes.
+    
+-   The base class is able to provide all of the operations that a derived class may need to perform.
+    
+-   There is behavioral overlap in the subclasses and you want to make it easier to share code between them.
+    
+-   You want to minimize coupling between those derived classes and the rest of the program.
+  
+## Credits  
+  
+* [Game Programming Patterns - Subclass Sandbox]([http://gameprogrammingpatterns.com/subclass-sandbox.html](http://gameprogrammingpatterns.com/subclass-sandbox.html))
\ No newline at end of file
diff --git a/subclass-sandbox/pom.xml b/subclass-sandbox/pom.xml
new file mode 100644
index 000000000000..8016ba471ed0
--- /dev/null
+++ b/subclass-sandbox/pom.xml
@@ -0,0 +1,49 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    The MIT License
+    Copyright ? 2014 Ilkka Sepp?l?
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>java-design-patterns</artifactId>
+        <groupId>com.iluwatar</groupId>
+        <version>1.22.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>subclass-sandbox</artifactId>
+
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.github.stefanbirkner</groupId>
+            <artifactId>system-rules</artifactId>
+        </dependency>
+    </dependencies>
+
+</project>
\ No newline at end of file
diff --git a/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/App.java b/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/App.java
new file mode 100644
index 000000000000..2e1f41c056c4
--- /dev/null
+++ b/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/App.java
@@ -0,0 +1,53 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.subclasssandbox;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * The subclass sandbox pattern describes a basic idea, while not having a lot
+ * of detailed mechanics. You will need the pattern when you have several similar
+ * subclasses. If you have to make a tiny change, then change the base class,
+ * while all subclasses shouldn't have to be touched. So the base class has to be
+ * able to provide all of the operations a derived class needs to perform.
+ */
+public class App {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
+
+  /**
+   * Entry point of the main program.
+   * @param args Program runtime arguments.
+   */
+  public static void main(String[] args) {
+    LOGGER.info("Use superpower: sky launch");
+    var skyLaunch = new SkyLaunch();
+    skyLaunch.activate();
+    LOGGER.info("Use superpower: ground dive");
+    var groundDive = new GroundDive();
+    groundDive.activate();
+  }
+
+}
diff --git a/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/GroundDive.java b/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/GroundDive.java
new file mode 100644
index 000000000000..f284e125fba7
--- /dev/null
+++ b/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/GroundDive.java
@@ -0,0 +1,44 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.subclasssandbox;
+
+import org.slf4j.LoggerFactory;
+
+/**
+ * GroundDive superpower.
+ */
+public class GroundDive extends Superpower {
+
+  public GroundDive() {
+    super();
+    logger = LoggerFactory.getLogger(GroundDive.class);
+  }
+
+  @Override
+  protected void activate() {
+    move(0, 0, -20);
+    playSound("GROUNDDIVE_SOUND", 5);
+    spawnParticles("GROUNDDIVE_PARTICLE", 20);
+  }
+}
diff --git a/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/SkyLaunch.java b/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/SkyLaunch.java
new file mode 100644
index 000000000000..16c94bd0ca57
--- /dev/null
+++ b/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/SkyLaunch.java
@@ -0,0 +1,44 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.subclasssandbox;
+
+import org.slf4j.LoggerFactory;
+
+/**
+ * SkyLaunch superpower.
+ */
+public class SkyLaunch extends Superpower {
+
+  public SkyLaunch() {
+    super();
+    logger = LoggerFactory.getLogger(SkyLaunch.class);
+  }
+
+  @Override
+  protected void activate() {
+    move(0, 0, 20);
+    playSound("SKYLAUNCH_SOUND", 1);
+    spawnParticles("SKYLAUNCH_PARTICLE", 100);
+  }
+}
diff --git a/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/Superpower.java b/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/Superpower.java
new file mode 100644
index 000000000000..d4875d586d62
--- /dev/null
+++ b/subclass-sandbox/src/main/java/com/iluwatar/subclasssandbox/Superpower.java
@@ -0,0 +1,69 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.subclasssandbox;
+
+import org.slf4j.Logger;
+
+/**
+ * Superpower abstract class. In this class the basic operations of all types of
+ * superpowers are provided as protected methods.
+ */
+public abstract class Superpower {
+
+  protected Logger logger;
+
+  /**
+   * Subclass of superpower should implement this sandbox method by calling the
+   * methods provided in this super class.
+   */
+  protected abstract void activate();
+
+  /**
+   * Move to (x, y, z).
+   * @param x X coordinate.
+   * @param y Y coordinate.
+   * @param z Z coordinate.
+   */
+  protected void move(double x, double y, double z) {
+    logger.info("Move to ( " + x + ", " + y + ", " + z + " )");
+  }
+
+  /**
+   * Play sound effect for the superpower.
+   * @param soundName Sound name.
+   * @param volumn Value of volumn.
+   */
+  protected void playSound(String soundName, int volumn) {
+    logger.info("Play " + soundName + " with volumn " + volumn);
+  }
+
+  /**
+   * Spawn particles for the superpower.
+   * @param particleType Particle type.
+   * @param count Count of particles to be spawned.
+   */
+  protected void spawnParticles(String particleType, int count) {
+    logger.info("Spawn " + count + " particle with type " + particleType);
+  }
+}


Test patch:
diff --git a/subclass-sandbox/src/test/java/com/iluwatar/subclasssandbox/AppTest.java b/subclass-sandbox/src/test/java/com/iluwatar/subclasssandbox/AppTest.java
new file mode 100644
index 000000000000..207c71ef9ef0
--- /dev/null
+++ b/subclass-sandbox/src/test/java/com/iluwatar/subclasssandbox/AppTest.java
@@ -0,0 +1,38 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.subclasssandbox;
+
+import org.junit.Test;
+
+/**
+ * App unit tests.
+ */
+public class AppTest {
+
+  @Test
+  public void testMain() {
+    String[] args = {};
+    App.main(args);
+  }
+}
diff --git a/subclass-sandbox/src/test/java/com/iluwatar/subclasssandbox/GroundDiveTest.java b/subclass-sandbox/src/test/java/com/iluwatar/subclasssandbox/GroundDiveTest.java
new file mode 100644
index 000000000000..7b4645742376
--- /dev/null
+++ b/subclass-sandbox/src/test/java/com/iluwatar/subclasssandbox/GroundDiveTest.java
@@ -0,0 +1,92 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.subclasssandbox;
+
+import org.junit.Assert;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.contrib.java.lang.system.SystemOutRule;
+
+/**
+ * GroundDive unit tests.
+ */
+public class GroundDiveTest {
+
+  @Rule
+  public SystemOutRule log = new SystemOutRule().enableLog();
+
+  @Test
+  public void testMove() {
+    log.clearLog();
+    var groundDive = new GroundDive();
+    groundDive.move(1.0, 1.0, 1.0);
+    var outputLog = getLogContent(log.getLog());
+    var expectedLog = "Move to ( 1.0, 1.0, 1.0 )";
+    Assert.assertEquals(outputLog, expectedLog);
+  }
+
+  @Test
+  public void testPlaySound() {
+    log.clearLog();
+    var groundDive = new GroundDive();
+    groundDive.playSound("SOUND_NAME", 1);
+    var outputLog = getLogContent(log.getLog());
+    var expectedLog = "Play SOUND_NAME with volumn 1";
+    Assert.assertEquals(outputLog, expectedLog);
+  }
+
+  @Test
+  public void testSpawnParticles() {
+    log.clearLog();
+    var groundDive = new GroundDive();
+    groundDive.spawnParticles("PARTICLE_TYPE", 100);
+    final var outputLog = getLogContent(log.getLog());
+    final var expectedLog = "Spawn 100 particle with type PARTICLE_TYPE";
+    Assert.assertEquals(outputLog, expectedLog);
+  }
+
+  @Test
+  public void testActivate() {
+    log.clearLog();
+    var groundDive = new GroundDive();
+    groundDive.activate();;
+    String[] logs = log.getLog().split("\n");
+    final var expectedSize = 3;
+    final var log1 = logs[0].split("-")[1].trim() + " -" + logs[0].split("-")[2].trim();
+    final var expectedLog1 = "Move to ( 0.0, 0.0, -20.0 )";
+    final var log2 = getLogContent(logs[1]);
+    final var expectedLog2 = "Play GROUNDDIVE_SOUND with volumn 5";
+    final var log3 = getLogContent(logs[2]);
+    final var expectedLog3 = "Spawn 20 particle with type GROUNDDIVE_PARTICLE";
+    Assert.assertEquals(logs.length, expectedSize);
+    Assert.assertEquals(log1, expectedLog1);
+    Assert.assertEquals(log2, expectedLog2);
+    Assert.assertEquals(log3, expectedLog3);
+  }
+
+  private String getLogContent(String log) {
+    return log.split("-")[1].trim();
+  }
+
+}
diff --git a/subclass-sandbox/src/test/java/com/iluwatar/subclasssandbox/SkyLaunchTest.java b/subclass-sandbox/src/test/java/com/iluwatar/subclasssandbox/SkyLaunchTest.java
new file mode 100644
index 000000000000..5ba84c0b55cc
--- /dev/null
+++ b/subclass-sandbox/src/test/java/com/iluwatar/subclasssandbox/SkyLaunchTest.java
@@ -0,0 +1,91 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.subclasssandbox;
+
+import org.junit.Assert;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.contrib.java.lang.system.SystemOutRule;
+
+/**
+ * SkyLaunch unit tests.
+ */
+public class SkyLaunchTest {
+
+  @Rule
+  public SystemOutRule log = new SystemOutRule().enableLog();
+
+  @Test
+  public void testMove() {
+    log.clearLog();
+    var skyLaunch = new SkyLaunch();
+    skyLaunch.move(1.0, 1.0, 1.0);
+    var outputLog = getLogContent(log.getLog());
+    var expectedLog = "Move to ( 1.0, 1.0, 1.0 )";
+    Assert.assertEquals(outputLog, expectedLog);
+  }
+
+  @Test
+  public void testPlaySound() {
+    log.clearLog();
+    var skyLaunch = new SkyLaunch();
+    skyLaunch.playSound("SOUND_NAME", 1);
+    var outputLog = getLogContent(log.getLog());
+    var expectedLog = "Play SOUND_NAME with volumn 1";
+    Assert.assertEquals(outputLog, expectedLog);
+  }
+
+  @Test
+  public void testSpawnParticles() {
+    log.clearLog();
+    var skyLaunch = new SkyLaunch();
+    skyLaunch.spawnParticles("PARTICLE_TYPE", 100);
+    var outputLog = getLogContent(log.getLog());
+    var expectedLog = "Spawn 100 particle with type PARTICLE_TYPE";
+    Assert.assertEquals(outputLog, expectedLog);
+  }
+
+  @Test
+  public void testActivate() {
+    log.clearLog();
+    var skyLaunch = new SkyLaunch();
+    skyLaunch.activate();;
+    String[] logs = log.getLog().split("\n");
+    final var expectedSize = 3;
+    final var log1 = getLogContent(logs[0]);
+    final var expectedLog1 = "Move to ( 0.0, 0.0, 20.0 )";
+    final var log2 = getLogContent(logs[1]);
+    final var expectedLog2 = "Play SKYLAUNCH_SOUND with volumn 1";
+    final var log3 = getLogContent(logs[2]);
+    final var expectedLog3 = "Spawn 100 particle with type SKYLAUNCH_PARTICLE";
+    Assert.assertEquals(logs.length, expectedSize);
+    Assert.assertEquals(log1, expectedLog1);
+    Assert.assertEquals(log2, expectedLog2);
+    Assert.assertEquals(log3, expectedLog3);
+  }
+
+  private String getLogContent(String log) {
+    return log.split("-")[1].trim();
+  }
+}