diff --git a/Behavioral/ChainOfResponsibilities/Handler.php b/Behavioral/ChainOfResponsibilities/Handler.php
index 7599cbb..595d7d1 100644
--- a/Behavioral/ChainOfResponsibilities/Handler.php
+++ b/Behavioral/ChainOfResponsibilities/Handler.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\ChainOfResponsibilities;
 
diff --git a/Behavioral/ChainOfResponsibilities/Responsible/HttpInMemoryCacheHandler.php b/Behavioral/ChainOfResponsibilities/Responsible/HttpInMemoryCacheHandler.php
index 9391ceb..631e551 100644
--- a/Behavioral/ChainOfResponsibilities/Responsible/HttpInMemoryCacheHandler.php
+++ b/Behavioral/ChainOfResponsibilities/Responsible/HttpInMemoryCacheHandler.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\ChainOfResponsibilities\Responsible;
 
diff --git a/Behavioral/ChainOfResponsibilities/Responsible/SlowDatabaseHandler.php b/Behavioral/ChainOfResponsibilities/Responsible/SlowDatabaseHandler.php
index 975ed42..1d25993 100644
--- a/Behavioral/ChainOfResponsibilities/Responsible/SlowDatabaseHandler.php
+++ b/Behavioral/ChainOfResponsibilities/Responsible/SlowDatabaseHandler.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\ChainOfResponsibilities\Responsible;
 
diff --git a/Behavioral/ChainOfResponsibilities/Tests/ChainTest.php b/Behavioral/ChainOfResponsibilities/Tests/ChainTest.php
index e9d4cb4..f5085d4 100644
--- a/Behavioral/ChainOfResponsibilities/Tests/ChainTest.php
+++ b/Behavioral/ChainOfResponsibilities/Tests/ChainTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\ChainOfResponsibilities\Tests;
 
diff --git a/Behavioral/ChainOfResponsibilities/uml/ChainOfResponsibilities.uml b/Behavioral/ChainOfResponsibilities/uml/ChainOfResponsibilities.uml
index 3b79650..1dc22b9 100644
--- a/Behavioral/ChainOfResponsibilities/uml/ChainOfResponsibilities.uml
+++ b/Behavioral/ChainOfResponsibilities/uml/ChainOfResponsibilities.uml
@@ -1,36 +1,20 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<Diagram>
-  <ID>PHP</ID>
-  <OriginalElement>\DesignPatterns\Behavioral\ChainOfResponsibilities\Handler</OriginalElement>
-  <nodes>
-    <node x="54.5" y="0.0">\DesignPatterns\Behavioral\ChainOfResponsibilities\Handler</node>
-    <node x="0.0" y="158.0">\DesignPatterns\Behavioral\ChainOfResponsibilities\Responsible\SlowStorage</node>
-    <node x="154.0" y="158.0">\DesignPatterns\Behavioral\ChainOfResponsibilities\Responsible\FastStorage</node>
-    <node x="304.0" y="45.0">\DesignPatterns\Behavioral\ChainOfResponsibilities\Request</node>
-  </nodes>
-  <notes />
-  <edges>
-    <edge source="\DesignPatterns\Behavioral\ChainOfResponsibilities\Responsible\SlowStorage" target="\DesignPatterns\Behavioral\ChainOfResponsibilities\Handler">
-      <point x="0.0" y="-44.5" />
-      <point x="67.0" y="133.0" />
-      <point x="99.25" y="133.0" />
-      <point x="-44.75" y="54.0" />
-    </edge>
-    <edge source="\DesignPatterns\Behavioral\ChainOfResponsibilities\Responsible\FastStorage" target="\DesignPatterns\Behavioral\ChainOfResponsibilities\Handler">
-      <point x="0.0" y="-44.5" />
-      <point x="221.0" y="133.0" />
-      <point x="188.75" y="133.0" />
-      <point x="44.75" y="54.0" />
-    </edge>
-  </edges>
-  <settings layout="Hierarchic Group" zoom="1.0" x="188.0" y="123.5" />
-  <SelectedNodes />
-  <Categories>
-    <Category>Fields</Category>
-    <Category>Constants</Category>
-    <Category>Constructors</Category>
-    <Category>Methods</Category>
-  </Categories>
-  <VISIBILITY>private</VISIBILITY>
-</Diagram>
-
+<?xml version="1.0" encoding="UTF-8"?>
+<Diagram>
+  <ID>PHP</ID>
+  <OriginalElement>\DesignPatterns\Behavioral\ChainOfResponsibilities\Handler</OriginalElement>
+  <nodes>
+    <node x="0.0" y="0.0">\DesignPatterns\Behavioral\ChainOfResponsibilities\Handler</node>
+  </nodes>
+  <notes />
+  <edges />
+  <settings layout="Hierarchic Group" zoom="1.0" x="537.5" y="338.0" />
+  <SelectedNodes />
+  <Categories>
+    <Category>Fields</Category>
+    <Category>Constants</Category>
+    <Category>Constructors</Category>
+    <Category>Methods</Category>
+  </Categories>
+  <VISIBILITY>private</VISIBILITY>
+</Diagram>
+
diff --git a/Behavioral/Command/AddMessageDateCommand.php b/Behavioral/Command/AddMessageDateCommand.php
index fcaeb4f..e37d0dd 100644
--- a/Behavioral/Command/AddMessageDateCommand.php
+++ b/Behavioral/Command/AddMessageDateCommand.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Command;
 
diff --git a/Behavioral/Command/CommandInterface.php b/Behavioral/Command/CommandInterface.php
index 265e862..db98ef7 100644
--- a/Behavioral/Command/CommandInterface.php
+++ b/Behavioral/Command/CommandInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Command;
 
diff --git a/Behavioral/Command/HelloCommand.php b/Behavioral/Command/HelloCommand.php
index 1dbfaf5..b5eb316 100644
--- a/Behavioral/Command/HelloCommand.php
+++ b/Behavioral/Command/HelloCommand.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Command;
 
diff --git a/Behavioral/Command/Invoker.php b/Behavioral/Command/Invoker.php
index c6e7f93..8c0e3a0 100644
--- a/Behavioral/Command/Invoker.php
+++ b/Behavioral/Command/Invoker.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Command;
 
diff --git a/Behavioral/Command/Receiver.php b/Behavioral/Command/Receiver.php
index 7ca6343..4eda52b 100644
--- a/Behavioral/Command/Receiver.php
+++ b/Behavioral/Command/Receiver.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Command;
 
diff --git a/Behavioral/Command/Tests/CommandTest.php b/Behavioral/Command/Tests/CommandTest.php
index e14e215..b10398c 100644
--- a/Behavioral/Command/Tests/CommandTest.php
+++ b/Behavioral/Command/Tests/CommandTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Command\Tests;
 
diff --git a/Behavioral/Command/Tests/UndoableCommandTest.php b/Behavioral/Command/Tests/UndoableCommandTest.php
index b76c17b..a79f471 100644
--- a/Behavioral/Command/Tests/UndoableCommandTest.php
+++ b/Behavioral/Command/Tests/UndoableCommandTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Command\Tests;
 
diff --git a/Behavioral/Command/UndoableCommandInterface.php b/Behavioral/Command/UndoableCommandInterface.php
index 52b02e9..491d695 100644
--- a/Behavioral/Command/UndoableCommandInterface.php
+++ b/Behavioral/Command/UndoableCommandInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Command;
 
diff --git a/Behavioral/Iterator/Book.php b/Behavioral/Iterator/Book.php
index bb9abeb..71cf460 100644
--- a/Behavioral/Iterator/Book.php
+++ b/Behavioral/Iterator/Book.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Iterator;
 
diff --git a/Behavioral/Iterator/BookList.php b/Behavioral/Iterator/BookList.php
index f8d0c87..e118565 100644
--- a/Behavioral/Iterator/BookList.php
+++ b/Behavioral/Iterator/BookList.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Iterator;
 
diff --git a/Behavioral/Iterator/Tests/IteratorTest.php b/Behavioral/Iterator/Tests/IteratorTest.php
index ed8c830..1f18cff 100644
--- a/Behavioral/Iterator/Tests/IteratorTest.php
+++ b/Behavioral/Iterator/Tests/IteratorTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Iterator\Tests;
 
diff --git a/Behavioral/Mediator/Colleague.php b/Behavioral/Mediator/Colleague.php
index 3a83742..29cc21b 100644
--- a/Behavioral/Mediator/Colleague.php
+++ b/Behavioral/Mediator/Colleague.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Mediator;
 
diff --git a/Behavioral/Mediator/Mediator.php b/Behavioral/Mediator/Mediator.php
index 08e1b71..30a94fd 100644
--- a/Behavioral/Mediator/Mediator.php
+++ b/Behavioral/Mediator/Mediator.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Mediator;
 
diff --git a/Behavioral/Mediator/MediatorInterface.php b/Behavioral/Mediator/MediatorInterface.php
index 5ec717a..c964034 100644
--- a/Behavioral/Mediator/MediatorInterface.php
+++ b/Behavioral/Mediator/MediatorInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Mediator;
 
diff --git a/Behavioral/Mediator/Subsystem/Client.php b/Behavioral/Mediator/Subsystem/Client.php
index 79a472d..16026b3 100644
--- a/Behavioral/Mediator/Subsystem/Client.php
+++ b/Behavioral/Mediator/Subsystem/Client.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Mediator\Subsystem;
 
diff --git a/Behavioral/Mediator/Subsystem/Database.php b/Behavioral/Mediator/Subsystem/Database.php
index 9255f22..5e07fdc 100644
--- a/Behavioral/Mediator/Subsystem/Database.php
+++ b/Behavioral/Mediator/Subsystem/Database.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Mediator\Subsystem;
 
diff --git a/Behavioral/Mediator/Subsystem/Server.php b/Behavioral/Mediator/Subsystem/Server.php
index c05be5e..883b21f 100644
--- a/Behavioral/Mediator/Subsystem/Server.php
+++ b/Behavioral/Mediator/Subsystem/Server.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Mediator\Subsystem;
 
diff --git a/Behavioral/Mediator/Tests/MediatorTest.php b/Behavioral/Mediator/Tests/MediatorTest.php
index 31a4b77..983b01e 100644
--- a/Behavioral/Mediator/Tests/MediatorTest.php
+++ b/Behavioral/Mediator/Tests/MediatorTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Tests\Mediator\Tests;
 
diff --git a/Behavioral/Memento/Memento.php b/Behavioral/Memento/Memento.php
index f75fcc9..e7b01d0 100644
--- a/Behavioral/Memento/Memento.php
+++ b/Behavioral/Memento/Memento.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Memento;
 
diff --git a/Behavioral/Memento/State.php b/Behavioral/Memento/State.php
index 6cb5dd1..30b4450 100644
--- a/Behavioral/Memento/State.php
+++ b/Behavioral/Memento/State.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Memento;
 
diff --git a/Behavioral/Memento/Tests/MementoTest.php b/Behavioral/Memento/Tests/MementoTest.php
index 8bcd42b..c5c74fc 100644
--- a/Behavioral/Memento/Tests/MementoTest.php
+++ b/Behavioral/Memento/Tests/MementoTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Memento\Tests;
 
diff --git a/Behavioral/Memento/Ticket.php b/Behavioral/Memento/Ticket.php
index 13f75e7..00ff42d 100644
--- a/Behavioral/Memento/Ticket.php
+++ b/Behavioral/Memento/Ticket.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Memento;
 
diff --git a/Behavioral/NullObject/LoggerInterface.php b/Behavioral/NullObject/LoggerInterface.php
index 7c1ff7d..fe6a269 100644
--- a/Behavioral/NullObject/LoggerInterface.php
+++ b/Behavioral/NullObject/LoggerInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\NullObject;
 
diff --git a/Behavioral/NullObject/NullLogger.php b/Behavioral/NullObject/NullLogger.php
index afddbd6..2d8b76a 100644
--- a/Behavioral/NullObject/NullLogger.php
+++ b/Behavioral/NullObject/NullLogger.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\NullObject;
 
diff --git a/Behavioral/NullObject/PrintLogger.php b/Behavioral/NullObject/PrintLogger.php
index 6c1d4ba..37f47b6 100644
--- a/Behavioral/NullObject/PrintLogger.php
+++ b/Behavioral/NullObject/PrintLogger.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\NullObject;
 
diff --git a/Behavioral/NullObject/Service.php b/Behavioral/NullObject/Service.php
index 81baf8f..b44714e 100644
--- a/Behavioral/NullObject/Service.php
+++ b/Behavioral/NullObject/Service.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\NullObject;
 
diff --git a/Behavioral/NullObject/Tests/LoggerTest.php b/Behavioral/NullObject/Tests/LoggerTest.php
index 9b74c35..7dbef0d 100644
--- a/Behavioral/NullObject/Tests/LoggerTest.php
+++ b/Behavioral/NullObject/Tests/LoggerTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\NullObject\Tests;
 
diff --git a/Behavioral/Observer/Tests/ObserverTest.php b/Behavioral/Observer/Tests/ObserverTest.php
index d7762d8..d815fd8 100644
--- a/Behavioral/Observer/Tests/ObserverTest.php
+++ b/Behavioral/Observer/Tests/ObserverTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Observer\Tests;
 
diff --git a/Behavioral/Observer/User.php b/Behavioral/Observer/User.php
index 6fd58d4..e68ae8c 100644
--- a/Behavioral/Observer/User.php
+++ b/Behavioral/Observer/User.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Observer;
 
diff --git a/Behavioral/Observer/UserObserver.php b/Behavioral/Observer/UserObserver.php
index 243e740..357247d 100644
--- a/Behavioral/Observer/UserObserver.php
+++ b/Behavioral/Observer/UserObserver.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Observer;
 
diff --git a/Behavioral/Specification/AndSpecification.php b/Behavioral/Specification/AndSpecification.php
index 5a7d99c..48c728a 100644
--- a/Behavioral/Specification/AndSpecification.php
+++ b/Behavioral/Specification/AndSpecification.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Specification;
 
diff --git a/Behavioral/Specification/Item.php b/Behavioral/Specification/Item.php
index a167f0a..ff5d316 100644
--- a/Behavioral/Specification/Item.php
+++ b/Behavioral/Specification/Item.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Specification;
 
diff --git a/Behavioral/Specification/NotSpecification.php b/Behavioral/Specification/NotSpecification.php
index db47b51..391ff7b 100644
--- a/Behavioral/Specification/NotSpecification.php
+++ b/Behavioral/Specification/NotSpecification.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Specification;
 
diff --git a/Behavioral/Specification/OrSpecification.php b/Behavioral/Specification/OrSpecification.php
index 47faaaa..fde61e4 100644
--- a/Behavioral/Specification/OrSpecification.php
+++ b/Behavioral/Specification/OrSpecification.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Specification;
 
diff --git a/Behavioral/Specification/PriceSpecification.php b/Behavioral/Specification/PriceSpecification.php
index 3b54586..bae1405 100644
--- a/Behavioral/Specification/PriceSpecification.php
+++ b/Behavioral/Specification/PriceSpecification.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Specification;
 
diff --git a/Behavioral/Specification/SpecificationInterface.php b/Behavioral/Specification/SpecificationInterface.php
index 7387700..51d9c43 100644
--- a/Behavioral/Specification/SpecificationInterface.php
+++ b/Behavioral/Specification/SpecificationInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Specification;
 
diff --git a/Behavioral/Specification/Tests/SpecificationTest.php b/Behavioral/Specification/Tests/SpecificationTest.php
index 34e4db4..6d11e40 100644
--- a/Behavioral/Specification/Tests/SpecificationTest.php
+++ b/Behavioral/Specification/Tests/SpecificationTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Specification\Tests;
 
diff --git a/Behavioral/State/OrderContext.php b/Behavioral/State/OrderContext.php
index 183ea98..2d9ccc2 100644
--- a/Behavioral/State/OrderContext.php
+++ b/Behavioral/State/OrderContext.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\State;
 
diff --git a/Behavioral/State/State.php b/Behavioral/State/State.php
index a6d4218..a7ecc5c 100644
--- a/Behavioral/State/State.php
+++ b/Behavioral/State/State.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\State;
 
diff --git a/Behavioral/State/StateCreated.php b/Behavioral/State/StateCreated.php
index 853213a..1e12b6c 100644
--- a/Behavioral/State/StateCreated.php
+++ b/Behavioral/State/StateCreated.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\State;
 
diff --git a/Behavioral/State/StateDone.php b/Behavioral/State/StateDone.php
index 355aa7e..f81940f 100644
--- a/Behavioral/State/StateDone.php
+++ b/Behavioral/State/StateDone.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\State;
 
diff --git a/Behavioral/State/StateShipped.php b/Behavioral/State/StateShipped.php
index f891b00..ea7b1ca 100644
--- a/Behavioral/State/StateShipped.php
+++ b/Behavioral/State/StateShipped.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\State;
 
diff --git a/Behavioral/State/Tests/StateTest.php b/Behavioral/State/Tests/StateTest.php
index 73273bc..026d960 100644
--- a/Behavioral/State/Tests/StateTest.php
+++ b/Behavioral/State/Tests/StateTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\State\Tests;
 
diff --git a/Behavioral/Strategy/ComparatorInterface.php b/Behavioral/Strategy/ComparatorInterface.php
index 4c5dcb2..233e148 100644
--- a/Behavioral/Strategy/ComparatorInterface.php
+++ b/Behavioral/Strategy/ComparatorInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Strategy;
 
diff --git a/Behavioral/Strategy/Context.php b/Behavioral/Strategy/Context.php
index 6478492..e8e5290 100644
--- a/Behavioral/Strategy/Context.php
+++ b/Behavioral/Strategy/Context.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Strategy;
 
diff --git a/Behavioral/Strategy/DateComparator.php b/Behavioral/Strategy/DateComparator.php
index 3f59667..d53c1bf 100644
--- a/Behavioral/Strategy/DateComparator.php
+++ b/Behavioral/Strategy/DateComparator.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Strategy;
 
diff --git a/Behavioral/Strategy/IdComparator.php b/Behavioral/Strategy/IdComparator.php
index 80c43cc..57ca2a7 100644
--- a/Behavioral/Strategy/IdComparator.php
+++ b/Behavioral/Strategy/IdComparator.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Strategy;
 
diff --git a/Behavioral/Strategy/Tests/StrategyTest.php b/Behavioral/Strategy/Tests/StrategyTest.php
index 69f4dca..20a5799 100644
--- a/Behavioral/Strategy/Tests/StrategyTest.php
+++ b/Behavioral/Strategy/Tests/StrategyTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Strategy\Tests;
 
diff --git a/Behavioral/TemplateMethod/BeachJourney.php b/Behavioral/TemplateMethod/BeachJourney.php
index 5007054..2f408f7 100644
--- a/Behavioral/TemplateMethod/BeachJourney.php
+++ b/Behavioral/TemplateMethod/BeachJourney.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\TemplateMethod;
 
diff --git a/Behavioral/TemplateMethod/CityJourney.php b/Behavioral/TemplateMethod/CityJourney.php
index f1f9335..999b074 100644
--- a/Behavioral/TemplateMethod/CityJourney.php
+++ b/Behavioral/TemplateMethod/CityJourney.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\TemplateMethod;
 
diff --git a/Behavioral/TemplateMethod/Journey.php b/Behavioral/TemplateMethod/Journey.php
index 0a1407c..9f24e54 100644
--- a/Behavioral/TemplateMethod/Journey.php
+++ b/Behavioral/TemplateMethod/Journey.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\TemplateMethod;
 
diff --git a/Behavioral/TemplateMethod/Tests/JourneyTest.php b/Behavioral/TemplateMethod/Tests/JourneyTest.php
index 7fbe673..2907f1e 100644
--- a/Behavioral/TemplateMethod/Tests/JourneyTest.php
+++ b/Behavioral/TemplateMethod/Tests/JourneyTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\TemplateMethod\Tests;
 
diff --git a/Behavioral/Visitor/Group.php b/Behavioral/Visitor/Group.php
index e4a9a65..5f2aab9 100644
--- a/Behavioral/Visitor/Group.php
+++ b/Behavioral/Visitor/Group.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Visitor;
 
diff --git a/Behavioral/Visitor/Role.php b/Behavioral/Visitor/Role.php
index 1a55c74..a5d0f90 100644
--- a/Behavioral/Visitor/Role.php
+++ b/Behavioral/Visitor/Role.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Visitor;
 
diff --git a/Behavioral/Visitor/RoleVisitor.php b/Behavioral/Visitor/RoleVisitor.php
index fc368b2..1489609 100644
--- a/Behavioral/Visitor/RoleVisitor.php
+++ b/Behavioral/Visitor/RoleVisitor.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Visitor;
 
diff --git a/Behavioral/Visitor/RoleVisitorInterface.php b/Behavioral/Visitor/RoleVisitorInterface.php
index b2aff5e..9cd2c87 100644
--- a/Behavioral/Visitor/RoleVisitorInterface.php
+++ b/Behavioral/Visitor/RoleVisitorInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Visitor;
 
diff --git a/Behavioral/Visitor/Tests/VisitorTest.php b/Behavioral/Visitor/Tests/VisitorTest.php
index e09cd2c..cd58544 100644
--- a/Behavioral/Visitor/Tests/VisitorTest.php
+++ b/Behavioral/Visitor/Tests/VisitorTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Tests\Visitor\Tests;
 
diff --git a/Behavioral/Visitor/User.php b/Behavioral/Visitor/User.php
index f3d9ad3..ccca2a3 100644
--- a/Behavioral/Visitor/User.php
+++ b/Behavioral/Visitor/User.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Behavioral\Visitor;
 
diff --git a/Creational/AbstractFactory/DigitalProduct.php b/Creational/AbstractFactory/DigitalProduct.php
index f4c3ac5..88158c2 100644
--- a/Creational/AbstractFactory/DigitalProduct.php
+++ b/Creational/AbstractFactory/DigitalProduct.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\AbstractFactory;
 
diff --git a/Creational/AbstractFactory/Product.php b/Creational/AbstractFactory/Product.php
index 5b4dcb9..54d7a26 100644
--- a/Creational/AbstractFactory/Product.php
+++ b/Creational/AbstractFactory/Product.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\AbstractFactory;
 
diff --git a/Creational/AbstractFactory/ProductFactory.php b/Creational/AbstractFactory/ProductFactory.php
index d0be2d2..94c87e3 100644
--- a/Creational/AbstractFactory/ProductFactory.php
+++ b/Creational/AbstractFactory/ProductFactory.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\AbstractFactory;
 
diff --git a/Creational/AbstractFactory/ShippableProduct.php b/Creational/AbstractFactory/ShippableProduct.php
index 83e7cd4..cd6d9bc 100644
--- a/Creational/AbstractFactory/ShippableProduct.php
+++ b/Creational/AbstractFactory/ShippableProduct.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\AbstractFactory;
 
diff --git a/Creational/AbstractFactory/Tests/AbstractFactoryTest.php b/Creational/AbstractFactory/Tests/AbstractFactoryTest.php
index cd49633..1477947 100644
--- a/Creational/AbstractFactory/Tests/AbstractFactoryTest.php
+++ b/Creational/AbstractFactory/Tests/AbstractFactoryTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\AbstractFactory\Tests;
 
diff --git a/Creational/AbstractFactory/uml/AbstractFactory.uml b/Creational/AbstractFactory/uml/AbstractFactory.uml
index 71303d2..96814c9 100644
--- a/Creational/AbstractFactory/uml/AbstractFactory.uml
+++ b/Creational/AbstractFactory/uml/AbstractFactory.uml
@@ -3,27 +3,27 @@
   <ID>PHP</ID>
   <OriginalElement>\DesignPatterns\Creational\AbstractFactory\DigitalProduct</OriginalElement>
   <nodes>
-    <node x="0.0" y="112.0">\DesignPatterns\Creational\AbstractFactory\DigitalProduct</node>
-    <node x="0.0" y="265.0">\DesignPatterns\Creational\AbstractFactory\ProductFactory</node>
-    <node x="204.0" y="101.0">\DesignPatterns\Creational\AbstractFactory\ShippableProduct</node>
-    <node x="147.5" y="0.0">\DesignPatterns\Creational\AbstractFactory\Product</node>
+    <node x="0.0" y="109.0">\DesignPatterns\Creational\AbstractFactory\DigitalProduct</node>
+    <node x="0.0" y="259.0">\DesignPatterns\Creational\AbstractFactory\ProductFactory</node>
+    <node x="166.0" y="98.0">\DesignPatterns\Creational\AbstractFactory\ShippableProduct</node>
+    <node x="128.5" y="0.0">\DesignPatterns\Creational\AbstractFactory\Product</node>
   </nodes>
   <notes />
   <edges>
     <edge source="\DesignPatterns\Creational\AbstractFactory\ShippableProduct" target="\DesignPatterns\Creational\AbstractFactory\Product">
-      <point x="0.0" y="-59.5" />
-      <point x="369.0" y="76.0" />
-      <point x="272.0" y="76.0" />
-      <point x="41.5" y="25.5" />
+      <point x="0.0" y="-58.0" />
+      <point x="312.0" y="73.0" />
+      <point x="224.5" y="73.0" />
+      <point x="32.0" y="24.0" />
     </edge>
     <edge source="\DesignPatterns\Creational\AbstractFactory\DigitalProduct" target="\DesignPatterns\Creational\AbstractFactory\Product">
-      <point x="0.0" y="-48.5" />
-      <point x="92.0" y="76.0" />
-      <point x="189.0" y="76.0" />
-      <point x="-41.5" y="25.5" />
+      <point x="0.0" y="-47.0" />
+      <point x="73.0" y="73.0" />
+      <point x="160.5" y="73.0" />
+      <point x="-32.0" y="24.0" />
     </edge>
   </edges>
-  <settings layout="Hierarchic Group" zoom="1.0" x="140.0" y="91.0" />
+  <settings layout="Hierarchic Group" zoom="1.0" x="537.5" y="256.0" />
   <SelectedNodes />
   <Categories>
     <Category>Fields</Category>
diff --git a/Creational/Builder/BuilderInterface.php b/Creational/Builder/BuilderInterface.php
index 3bcf961..1edc58f 100644
--- a/Creational/Builder/BuilderInterface.php
+++ b/Creational/Builder/BuilderInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Builder;
 
diff --git a/Creational/Builder/CarBuilder.php b/Creational/Builder/CarBuilder.php
index fb20822..6f2fee8 100644
--- a/Creational/Builder/CarBuilder.php
+++ b/Creational/Builder/CarBuilder.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Builder;
 
diff --git a/Creational/Builder/Director.php b/Creational/Builder/Director.php
index 9925d5a..e9c05f5 100644
--- a/Creational/Builder/Director.php
+++ b/Creational/Builder/Director.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Builder;
 
diff --git a/Creational/Builder/Parts/Car.php b/Creational/Builder/Parts/Car.php
index 53eb0d4..7f8ebfa 100644
--- a/Creational/Builder/Parts/Car.php
+++ b/Creational/Builder/Parts/Car.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Builder\Parts;
 
diff --git a/Creational/Builder/Parts/Door.php b/Creational/Builder/Parts/Door.php
index f2732fe..a0cd98c 100644
--- a/Creational/Builder/Parts/Door.php
+++ b/Creational/Builder/Parts/Door.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Builder\Parts;
 
diff --git a/Creational/Builder/Parts/Engine.php b/Creational/Builder/Parts/Engine.php
index 48046b8..572335d 100644
--- a/Creational/Builder/Parts/Engine.php
+++ b/Creational/Builder/Parts/Engine.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Builder\Parts;
 
diff --git a/Creational/Builder/Parts/Truck.php b/Creational/Builder/Parts/Truck.php
index 23c137c..4d82e29 100644
--- a/Creational/Builder/Parts/Truck.php
+++ b/Creational/Builder/Parts/Truck.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Builder\Parts;
 
diff --git a/Creational/Builder/Parts/Vehicle.php b/Creational/Builder/Parts/Vehicle.php
index c7e3c15..bfa848e 100644
--- a/Creational/Builder/Parts/Vehicle.php
+++ b/Creational/Builder/Parts/Vehicle.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Builder\Parts;
 
diff --git a/Creational/Builder/Parts/Wheel.php b/Creational/Builder/Parts/Wheel.php
index 4e677e3..5e2920a 100644
--- a/Creational/Builder/Parts/Wheel.php
+++ b/Creational/Builder/Parts/Wheel.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Builder\Parts;
 
diff --git a/Creational/Builder/Tests/DirectorTest.php b/Creational/Builder/Tests/DirectorTest.php
index 353758b..f83ebeb 100644
--- a/Creational/Builder/Tests/DirectorTest.php
+++ b/Creational/Builder/Tests/DirectorTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Builder\Tests;
 
diff --git a/Creational/Builder/TruckBuilder.php b/Creational/Builder/TruckBuilder.php
index e686eac..83b0928 100644
--- a/Creational/Builder/TruckBuilder.php
+++ b/Creational/Builder/TruckBuilder.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Builder;
 
diff --git a/Creational/FactoryMethod/FileLogger.php b/Creational/FactoryMethod/FileLogger.php
index 96aaa22..4619f44 100644
--- a/Creational/FactoryMethod/FileLogger.php
+++ b/Creational/FactoryMethod/FileLogger.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\FactoryMethod;
 
diff --git a/Creational/FactoryMethod/FileLoggerFactory.php b/Creational/FactoryMethod/FileLoggerFactory.php
index 6922c00..0466ddc 100644
--- a/Creational/FactoryMethod/FileLoggerFactory.php
+++ b/Creational/FactoryMethod/FileLoggerFactory.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\FactoryMethod;
 
diff --git a/Creational/FactoryMethod/Logger.php b/Creational/FactoryMethod/Logger.php
index 669ddf8..dc48e3e 100644
--- a/Creational/FactoryMethod/Logger.php
+++ b/Creational/FactoryMethod/Logger.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\FactoryMethod;
 
diff --git a/Creational/FactoryMethod/LoggerFactory.php b/Creational/FactoryMethod/LoggerFactory.php
index 181c09a..6f77eff 100644
--- a/Creational/FactoryMethod/LoggerFactory.php
+++ b/Creational/FactoryMethod/LoggerFactory.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\FactoryMethod;
 
diff --git a/Creational/FactoryMethod/StdoutLogger.php b/Creational/FactoryMethod/StdoutLogger.php
index 04e624a..413164c 100644
--- a/Creational/FactoryMethod/StdoutLogger.php
+++ b/Creational/FactoryMethod/StdoutLogger.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\FactoryMethod;
 
diff --git a/Creational/FactoryMethod/StdoutLoggerFactory.php b/Creational/FactoryMethod/StdoutLoggerFactory.php
index 3d53051..613fb91 100644
--- a/Creational/FactoryMethod/StdoutLoggerFactory.php
+++ b/Creational/FactoryMethod/StdoutLoggerFactory.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\FactoryMethod;
 
diff --git a/Creational/FactoryMethod/Tests/FactoryMethodTest.php b/Creational/FactoryMethod/Tests/FactoryMethodTest.php
index 7c78d23..3898edb 100644
--- a/Creational/FactoryMethod/Tests/FactoryMethodTest.php
+++ b/Creational/FactoryMethod/Tests/FactoryMethodTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\FactoryMethod\Tests;
 
diff --git a/Creational/Multiton/Multiton.php b/Creational/Multiton/Multiton.php
index d662f24..21bbeed 100644
--- a/Creational/Multiton/Multiton.php
+++ b/Creational/Multiton/Multiton.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Multiton;
 
diff --git a/Creational/Multiton/Tests/MultitonTest.php b/Creational/Multiton/Tests/MultitonTest.php
index bbe4f2a..624d65b 100644
--- a/Creational/Multiton/Tests/MultitonTest.php
+++ b/Creational/Multiton/Tests/MultitonTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Multition\Tests;
 
diff --git a/Creational/Pool/StringReverseWorker.php b/Creational/Pool/StringReverseWorker.php
index 92c2ce5..c61c287 100644
--- a/Creational/Pool/StringReverseWorker.php
+++ b/Creational/Pool/StringReverseWorker.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Pool;
 
diff --git a/Creational/Pool/Tests/PoolTest.php b/Creational/Pool/Tests/PoolTest.php
index b115d39..7222f15 100644
--- a/Creational/Pool/Tests/PoolTest.php
+++ b/Creational/Pool/Tests/PoolTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Pool\Tests;
 
diff --git a/Creational/Pool/WorkerPool.php b/Creational/Pool/WorkerPool.php
index 8cda11a..1d70e83 100644
--- a/Creational/Pool/WorkerPool.php
+++ b/Creational/Pool/WorkerPool.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Pool;
 
diff --git a/Creational/Prototype/BarBookPrototype.php b/Creational/Prototype/BarBookPrototype.php
index 5afadad..5b29e3e 100644
--- a/Creational/Prototype/BarBookPrototype.php
+++ b/Creational/Prototype/BarBookPrototype.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Prototype;
 
diff --git a/Creational/Prototype/BookPrototype.php b/Creational/Prototype/BookPrototype.php
index 2f4d55f..c1d8057 100644
--- a/Creational/Prototype/BookPrototype.php
+++ b/Creational/Prototype/BookPrototype.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Prototype;
 
diff --git a/Creational/Prototype/FooBookPrototype.php b/Creational/Prototype/FooBookPrototype.php
index 51550f9..26902a1 100644
--- a/Creational/Prototype/FooBookPrototype.php
+++ b/Creational/Prototype/FooBookPrototype.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Prototype;
 
diff --git a/Creational/Prototype/Tests/PrototypeTest.php b/Creational/Prototype/Tests/PrototypeTest.php
index 06eb280..6d84ece 100644
--- a/Creational/Prototype/Tests/PrototypeTest.php
+++ b/Creational/Prototype/Tests/PrototypeTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Prototype\Tests;
 
diff --git a/Creational/SimpleFactory/Bicycle.php b/Creational/SimpleFactory/Bicycle.php
index 552b986..0300c46 100644
--- a/Creational/SimpleFactory/Bicycle.php
+++ b/Creational/SimpleFactory/Bicycle.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\SimpleFactory;
 
diff --git a/Creational/SimpleFactory/SimpleFactory.php b/Creational/SimpleFactory/SimpleFactory.php
index bd49343..f28e079 100644
--- a/Creational/SimpleFactory/SimpleFactory.php
+++ b/Creational/SimpleFactory/SimpleFactory.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\SimpleFactory;
 
diff --git a/Creational/SimpleFactory/Tests/SimpleFactoryTest.php b/Creational/SimpleFactory/Tests/SimpleFactoryTest.php
index 0e144a5..adc652c 100644
--- a/Creational/SimpleFactory/Tests/SimpleFactoryTest.php
+++ b/Creational/SimpleFactory/Tests/SimpleFactoryTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\SimpleFactory\Tests;
 
diff --git a/Creational/Singleton/Singleton.php b/Creational/Singleton/Singleton.php
index c7cacc7..09f4bf0 100644
--- a/Creational/Singleton/Singleton.php
+++ b/Creational/Singleton/Singleton.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Singleton;
 
diff --git a/Creational/Singleton/Tests/SingletonTest.php b/Creational/Singleton/Tests/SingletonTest.php
index 663e058..17bb63d 100644
--- a/Creational/Singleton/Tests/SingletonTest.php
+++ b/Creational/Singleton/Tests/SingletonTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\Singleton\Tests;
 
diff --git a/Creational/StaticFactory/FormatNumber.php b/Creational/StaticFactory/FormatNumber.php
index 7579a92..a368d1d 100644
--- a/Creational/StaticFactory/FormatNumber.php
+++ b/Creational/StaticFactory/FormatNumber.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\StaticFactory;
 
diff --git a/Creational/StaticFactory/FormatString.php b/Creational/StaticFactory/FormatString.php
index 41e7221..70e706a 100644
--- a/Creational/StaticFactory/FormatString.php
+++ b/Creational/StaticFactory/FormatString.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\StaticFactory;
 
diff --git a/Creational/StaticFactory/Formatter.php b/Creational/StaticFactory/Formatter.php
index f6abe51..90787dc 100644
--- a/Creational/StaticFactory/Formatter.php
+++ b/Creational/StaticFactory/Formatter.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\StaticFactory;
 
diff --git a/Creational/StaticFactory/StaticFactory.php b/Creational/StaticFactory/StaticFactory.php
index b5a44ae..0b56382 100644
--- a/Creational/StaticFactory/StaticFactory.php
+++ b/Creational/StaticFactory/StaticFactory.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\StaticFactory;
 
diff --git a/Creational/StaticFactory/Tests/StaticFactoryTest.php b/Creational/StaticFactory/Tests/StaticFactoryTest.php
index e9f7712..398070f 100644
--- a/Creational/StaticFactory/Tests/StaticFactoryTest.php
+++ b/Creational/StaticFactory/Tests/StaticFactoryTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Creational\StaticFactory\Tests;
 
diff --git a/More/EAV/Attribute.php b/More/EAV/Attribute.php
index 10ac638..2ff5e47 100644
--- a/More/EAV/Attribute.php
+++ b/More/EAV/Attribute.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\EAV;
 
diff --git a/More/EAV/Entity.php b/More/EAV/Entity.php
index 96d6583..1affcb5 100644
--- a/More/EAV/Entity.php
+++ b/More/EAV/Entity.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\EAV;
 
diff --git a/More/EAV/Tests/EAVTest.php b/More/EAV/Tests/EAVTest.php
index c170a43..b6c2579 100644
--- a/More/EAV/Tests/EAVTest.php
+++ b/More/EAV/Tests/EAVTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\EAV\Tests;
 
diff --git a/More/EAV/Value.php b/More/EAV/Value.php
index f316728..31f7267 100644
--- a/More/EAV/Value.php
+++ b/More/EAV/Value.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\EAV;
 
diff --git a/More/Repository/Domain/Post.php b/More/Repository/Domain/Post.php
index ca67c3b..63f2a6e 100644
--- a/More/Repository/Domain/Post.php
+++ b/More/Repository/Domain/Post.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\Repository\Domain;
 
diff --git a/More/Repository/Domain/PostId.php b/More/Repository/Domain/PostId.php
index ceadc78..08b202f 100644
--- a/More/Repository/Domain/PostId.php
+++ b/More/Repository/Domain/PostId.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\Repository\Domain;
 
diff --git a/More/Repository/Domain/PostStatus.php b/More/Repository/Domain/PostStatus.php
index 90ef81b..172a45e 100644
--- a/More/Repository/Domain/PostStatus.php
+++ b/More/Repository/Domain/PostStatus.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\Repository\Domain;
 
diff --git a/More/Repository/InMemoryPersistence.php b/More/Repository/InMemoryPersistence.php
index b378321..69df0a8 100644
--- a/More/Repository/InMemoryPersistence.php
+++ b/More/Repository/InMemoryPersistence.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\Repository;
 
diff --git a/More/Repository/Persistence.php b/More/Repository/Persistence.php
index eed76b9..de3eb7e 100644
--- a/More/Repository/Persistence.php
+++ b/More/Repository/Persistence.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\Repository;
 
diff --git a/More/Repository/PostRepository.php b/More/Repository/PostRepository.php
index d06da37..e2557d4 100644
--- a/More/Repository/PostRepository.php
+++ b/More/Repository/PostRepository.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\Repository;
 
diff --git a/More/Repository/Tests/PostRepositoryTest.php b/More/Repository/Tests/PostRepositoryTest.php
index fec6ef1..95cb1e4 100644
--- a/More/Repository/Tests/PostRepositoryTest.php
+++ b/More/Repository/Tests/PostRepositoryTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\Repository\Tests;
 
diff --git a/More/ServiceLocator/LogService.php b/More/ServiceLocator/LogService.php
index fc5b1d9..a8fa10e 100644
--- a/More/ServiceLocator/LogService.php
+++ b/More/ServiceLocator/LogService.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\ServiceLocator;
 
diff --git a/More/ServiceLocator/ServiceLocator.php b/More/ServiceLocator/ServiceLocator.php
index 353c053..fe37c95 100644
--- a/More/ServiceLocator/ServiceLocator.php
+++ b/More/ServiceLocator/ServiceLocator.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\ServiceLocator;
 
diff --git a/More/ServiceLocator/Tests/ServiceLocatorTest.php b/More/ServiceLocator/Tests/ServiceLocatorTest.php
index 7abbae7..1ba356d 100644
--- a/More/ServiceLocator/Tests/ServiceLocatorTest.php
+++ b/More/ServiceLocator/Tests/ServiceLocatorTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\More\ServiceLocator\Tests;
 
diff --git a/Structural/Adapter/Book.php b/Structural/Adapter/Book.php
index 05d15cc..7460131 100644
--- a/Structural/Adapter/Book.php
+++ b/Structural/Adapter/Book.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Adapter;
 
diff --git a/Structural/Adapter/BookInterface.php b/Structural/Adapter/BookInterface.php
index 6ebabf4..3262f78 100644
--- a/Structural/Adapter/BookInterface.php
+++ b/Structural/Adapter/BookInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Adapter;
 
diff --git a/Structural/Adapter/EBookAdapter.php b/Structural/Adapter/EBookAdapter.php
index 0044a82..d4b5006 100644
--- a/Structural/Adapter/EBookAdapter.php
+++ b/Structural/Adapter/EBookAdapter.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Adapter;
 
diff --git a/Structural/Adapter/EBookInterface.php b/Structural/Adapter/EBookInterface.php
index bae5033..798495c 100644
--- a/Structural/Adapter/EBookInterface.php
+++ b/Structural/Adapter/EBookInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Adapter;
 
diff --git a/Structural/Adapter/Kindle.php b/Structural/Adapter/Kindle.php
index a150767..500c009 100644
--- a/Structural/Adapter/Kindle.php
+++ b/Structural/Adapter/Kindle.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Adapter;
 
diff --git a/Structural/Adapter/Tests/AdapterTest.php b/Structural/Adapter/Tests/AdapterTest.php
index 47636f0..a01a90d 100644
--- a/Structural/Adapter/Tests/AdapterTest.php
+++ b/Structural/Adapter/Tests/AdapterTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Adapter\Tests;
 
diff --git a/Structural/Bridge/Formatter.php b/Structural/Bridge/Formatter.php
index 7d161bf..9eb1bb8 100644
--- a/Structural/Bridge/Formatter.php
+++ b/Structural/Bridge/Formatter.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Bridge;
 
diff --git a/Structural/Bridge/HelloWorldService.php b/Structural/Bridge/HelloWorldService.php
index 5de12f0..0e90f29 100644
--- a/Structural/Bridge/HelloWorldService.php
+++ b/Structural/Bridge/HelloWorldService.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Bridge;
 
diff --git a/Structural/Bridge/HtmlFormatter.php b/Structural/Bridge/HtmlFormatter.php
index 043bc15..297b5b8 100644
--- a/Structural/Bridge/HtmlFormatter.php
+++ b/Structural/Bridge/HtmlFormatter.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Bridge;
 
diff --git a/Structural/Bridge/PingService.php b/Structural/Bridge/PingService.php
index f72cf81..e24fb80 100644
--- a/Structural/Bridge/PingService.php
+++ b/Structural/Bridge/PingService.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Bridge;
 
diff --git a/Structural/Bridge/PlainTextFormatter.php b/Structural/Bridge/PlainTextFormatter.php
index 1c36cb5..969771c 100644
--- a/Structural/Bridge/PlainTextFormatter.php
+++ b/Structural/Bridge/PlainTextFormatter.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Bridge;
 
diff --git a/Structural/Bridge/Service.php b/Structural/Bridge/Service.php
index 479b50f..5a5aa9b 100644
--- a/Structural/Bridge/Service.php
+++ b/Structural/Bridge/Service.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Bridge;
 
diff --git a/Structural/Bridge/Tests/BridgeTest.php b/Structural/Bridge/Tests/BridgeTest.php
index 10e3e58..32cb4db 100644
--- a/Structural/Bridge/Tests/BridgeTest.php
+++ b/Structural/Bridge/Tests/BridgeTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Bridge\Tests;
 
diff --git a/Structural/Composite/Form.php b/Structural/Composite/Form.php
index 6db2d3f..aa5b724 100644
--- a/Structural/Composite/Form.php
+++ b/Structural/Composite/Form.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Composite;
 
diff --git a/Structural/Composite/InputElement.php b/Structural/Composite/InputElement.php
index 0c437db..c856be9 100644
--- a/Structural/Composite/InputElement.php
+++ b/Structural/Composite/InputElement.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Composite;
 
diff --git a/Structural/Composite/RenderableInterface.php b/Structural/Composite/RenderableInterface.php
index 444f707..a75b242 100644
--- a/Structural/Composite/RenderableInterface.php
+++ b/Structural/Composite/RenderableInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Composite;
 
diff --git a/Structural/Composite/Tests/CompositeTest.php b/Structural/Composite/Tests/CompositeTest.php
index 90b8e12..262eb8d 100644
--- a/Structural/Composite/Tests/CompositeTest.php
+++ b/Structural/Composite/Tests/CompositeTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Composite\Tests;
 
diff --git a/Structural/Composite/TextElement.php b/Structural/Composite/TextElement.php
index 55a868b..ae268b9 100644
--- a/Structural/Composite/TextElement.php
+++ b/Structural/Composite/TextElement.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Composite;
 
diff --git a/Structural/DataMapper/StorageAdapter.php b/Structural/DataMapper/StorageAdapter.php
index 2c9caef..c669477 100644
--- a/Structural/DataMapper/StorageAdapter.php
+++ b/Structural/DataMapper/StorageAdapter.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\DataMapper;
 
diff --git a/Structural/DataMapper/Tests/DataMapperTest.php b/Structural/DataMapper/Tests/DataMapperTest.php
index fd03f45..1459544 100644
--- a/Structural/DataMapper/Tests/DataMapperTest.php
+++ b/Structural/DataMapper/Tests/DataMapperTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\DataMapper\Tests;
 
diff --git a/Structural/DataMapper/User.php b/Structural/DataMapper/User.php
index 8a6fd04..2590989 100644
--- a/Structural/DataMapper/User.php
+++ b/Structural/DataMapper/User.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\DataMapper;
 
diff --git a/Structural/DataMapper/UserMapper.php b/Structural/DataMapper/UserMapper.php
index 415246a..6ef2253 100644
--- a/Structural/DataMapper/UserMapper.php
+++ b/Structural/DataMapper/UserMapper.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\DataMapper;
 
diff --git a/Structural/Decorator/Booking.php b/Structural/Decorator/Booking.php
index 1ce0146..453ef81 100644
--- a/Structural/Decorator/Booking.php
+++ b/Structural/Decorator/Booking.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Decorator;
 
diff --git a/Structural/Decorator/BookingDecorator.php b/Structural/Decorator/BookingDecorator.php
index 3af2aad..cc001ad 100644
--- a/Structural/Decorator/BookingDecorator.php
+++ b/Structural/Decorator/BookingDecorator.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Decorator;
 
diff --git a/Structural/Decorator/DoubleRoomBooking.php b/Structural/Decorator/DoubleRoomBooking.php
index 9d745d7..aba57ac 100644
--- a/Structural/Decorator/DoubleRoomBooking.php
+++ b/Structural/Decorator/DoubleRoomBooking.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Decorator;
 
diff --git a/Structural/Decorator/ExtraBed.php b/Structural/Decorator/ExtraBed.php
index 8413349..9842cff 100644
--- a/Structural/Decorator/ExtraBed.php
+++ b/Structural/Decorator/ExtraBed.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Decorator;
 
diff --git a/Structural/Decorator/Tests/DecoratorTest.php b/Structural/Decorator/Tests/DecoratorTest.php
index 6576f90..81ef3e3 100644
--- a/Structural/Decorator/Tests/DecoratorTest.php
+++ b/Structural/Decorator/Tests/DecoratorTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Decorator\Tests;
 
diff --git a/Structural/Decorator/WiFi.php b/Structural/Decorator/WiFi.php
index 4226002..e9944ad 100644
--- a/Structural/Decorator/WiFi.php
+++ b/Structural/Decorator/WiFi.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Decorator;
 
diff --git a/Structural/DependencyInjection/DatabaseConfiguration.php b/Structural/DependencyInjection/DatabaseConfiguration.php
index 51d72d7..a101229 100644
--- a/Structural/DependencyInjection/DatabaseConfiguration.php
+++ b/Structural/DependencyInjection/DatabaseConfiguration.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\DependencyInjection;
 
diff --git a/Structural/DependencyInjection/DatabaseConnection.php b/Structural/DependencyInjection/DatabaseConnection.php
index b5af8ba..0d562d9 100644
--- a/Structural/DependencyInjection/DatabaseConnection.php
+++ b/Structural/DependencyInjection/DatabaseConnection.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\DependencyInjection;
 
diff --git a/Structural/DependencyInjection/Tests/DependencyInjectionTest.php b/Structural/DependencyInjection/Tests/DependencyInjectionTest.php
index e0e5bd2..d0c213a 100644
--- a/Structural/DependencyInjection/Tests/DependencyInjectionTest.php
+++ b/Structural/DependencyInjection/Tests/DependencyInjectionTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\DependencyInjection\Tests;
 
diff --git a/Structural/Facade/BiosInterface.php b/Structural/Facade/BiosInterface.php
index ba6bdbe..1b0cb7a 100644
--- a/Structural/Facade/BiosInterface.php
+++ b/Structural/Facade/BiosInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Facade;
 
diff --git a/Structural/Facade/Facade.php b/Structural/Facade/Facade.php
index bda8b46..8e7b3f2 100644
--- a/Structural/Facade/Facade.php
+++ b/Structural/Facade/Facade.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Facade;
 
diff --git a/Structural/Facade/OsInterface.php b/Structural/Facade/OsInterface.php
index 1b3a93e..9637f7c 100644
--- a/Structural/Facade/OsInterface.php
+++ b/Structural/Facade/OsInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Facade;
 
diff --git a/Structural/Facade/Tests/FacadeTest.php b/Structural/Facade/Tests/FacadeTest.php
index 0017eea..9afdc38 100644
--- a/Structural/Facade/Tests/FacadeTest.php
+++ b/Structural/Facade/Tests/FacadeTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Facade\Tests;
 
diff --git a/Structural/FluentInterface/Sql.php b/Structural/FluentInterface/Sql.php
index ed54992..c8813f4 100644
--- a/Structural/FluentInterface/Sql.php
+++ b/Structural/FluentInterface/Sql.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\FluentInterface;
 
diff --git a/Structural/FluentInterface/Tests/FluentInterfaceTest.php b/Structural/FluentInterface/Tests/FluentInterfaceTest.php
index 8cea81b..700674a 100644
--- a/Structural/FluentInterface/Tests/FluentInterfaceTest.php
+++ b/Structural/FluentInterface/Tests/FluentInterfaceTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\FluentInterface\Tests;
 
diff --git a/Structural/Flyweight/CharacterFlyweight.php b/Structural/Flyweight/CharacterFlyweight.php
index d1e7954..4ff5808 100644
--- a/Structural/Flyweight/CharacterFlyweight.php
+++ b/Structural/Flyweight/CharacterFlyweight.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Flyweight;
 
diff --git a/Structural/Flyweight/FlyweightFactory.php b/Structural/Flyweight/FlyweightFactory.php
index a295a22..25ab186 100644
--- a/Structural/Flyweight/FlyweightFactory.php
+++ b/Structural/Flyweight/FlyweightFactory.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Flyweight;
 
diff --git a/Structural/Flyweight/FlyweightInterface.php b/Structural/Flyweight/FlyweightInterface.php
index 032a1be..fab729d 100644
--- a/Structural/Flyweight/FlyweightInterface.php
+++ b/Structural/Flyweight/FlyweightInterface.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Flyweight;
 
diff --git a/Structural/Flyweight/Tests/FlyweightTest.php b/Structural/Flyweight/Tests/FlyweightTest.php
index 492d15b..1373107 100644
--- a/Structural/Flyweight/Tests/FlyweightTest.php
+++ b/Structural/Flyweight/Tests/FlyweightTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Flyweight\Tests;
 
diff --git a/Structural/Proxy/BankAccount.php b/Structural/Proxy/BankAccount.php
index 84fab34..4da6afb 100644
--- a/Structural/Proxy/BankAccount.php
+++ b/Structural/Proxy/BankAccount.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Proxy;
 
diff --git a/Structural/Proxy/BankAccountProxy.php b/Structural/Proxy/BankAccountProxy.php
index 85b46e5..6bfce7f 100644
--- a/Structural/Proxy/BankAccountProxy.php
+++ b/Structural/Proxy/BankAccountProxy.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Proxy;
 
diff --git a/Structural/Proxy/HeavyBankAccount.php b/Structural/Proxy/HeavyBankAccount.php
index 7fd8c17..d73a391 100644
--- a/Structural/Proxy/HeavyBankAccount.php
+++ b/Structural/Proxy/HeavyBankAccount.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Proxy;
 
diff --git a/Structural/Proxy/Tests/ProxyTest.php b/Structural/Proxy/Tests/ProxyTest.php
index ec62b48..56269b7 100644
--- a/Structural/Proxy/Tests/ProxyTest.php
+++ b/Structural/Proxy/Tests/ProxyTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Proxy\Tests;
 
diff --git a/Structural/Registry/Registry.php b/Structural/Registry/Registry.php
index dccaf6f..08161e7 100644
--- a/Structural/Registry/Registry.php
+++ b/Structural/Registry/Registry.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Registry;
 
diff --git a/Structural/Registry/Tests/RegistryTest.php b/Structural/Registry/Tests/RegistryTest.php
index a026415..266b8b1 100644
--- a/Structural/Registry/Tests/RegistryTest.php
+++ b/Structural/Registry/Tests/RegistryTest.php
@@ -1,4 +1,5 @@
 <?php
+declare(strict_types=1);
 
 namespace DesignPatterns\Structural\Registry\Tests;