diff --git a/Classes/Domain/Model/Addition.php b/Classes/Domain/Model/Addition.php
index 83f8727..03712c4 100644
--- a/Classes/Domain/Model/Addition.php
+++ b/Classes/Domain/Model/Addition.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Domain\Model;
 
 /*
@@ -30,7 +32,7 @@ class Addition extends \TYPO3\CMS\Extbase\DomainObject\AbstractValueObject
     /**
      * @return string $title
      */
-    public function getTitle()
+    public function getTitle(): string
     {
         return $this->title;
     }
@@ -40,7 +42,7 @@ class Addition extends \TYPO3\CMS\Extbase\DomainObject\AbstractValueObject
      *
      * @return void
      */
-    public function setTitle($title)
+    public function setTitle(string $title)
     {
         $this->title = $title;
     }
diff --git a/Classes/Domain/Model/TeaBeverage.php b/Classes/Domain/Model/TeaBeverage.php
index 9d1d3d9..805add7 100644
--- a/Classes/Domain/Model/TeaBeverage.php
+++ b/Classes/Domain/Model/TeaBeverage.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Domain\Model;
 
 /*
@@ -14,6 +16,8 @@ namespace OliverKlee\Tea\Domain\Model;
  * The TYPO3 project - inspiring people to share!
  */
 
+use TYPO3\CMS\Extbase\Persistence\ObjectStorage;
+
 /**
  * This model represents a good cup of tea.
  *
@@ -68,7 +72,7 @@ class TeaBeverage extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
     /**
      * @return float $size
      */
-    public function getSize()
+    public function getSize(): float
     {
         return $this->size;
     }
@@ -78,13 +82,13 @@ class TeaBeverage extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function setSize($size)
+    public function setSize(float $size)
     {
         $this->size = $size;
     }
 
     /**
-     * @return \OliverKlee\Tea\Domain\Model\TeaType $type
+     * @return TeaType|null $type
      */
     public function getType()
     {
@@ -92,11 +96,11 @@ class TeaBeverage extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
     }
 
     /**
-     * @param \OliverKlee\Tea\Domain\Model\TeaType $type
+     * @param TeaType $type
      *
      * @return void
      */
-    public function setType(\OliverKlee\Tea\Domain\Model\TeaType $type)
+    public function setType(TeaType $type)
     {
         $this->type = $type;
     }
@@ -104,7 +108,7 @@ class TeaBeverage extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
     /**
      * @return \TYPO3\CMS\Extbase\Persistence\ObjectStorage<\OliverKlee\Tea\Domain\Model\Addition> $additions
      */
-    public function getAdditions()
+    public function getAdditions(): ObjectStorage
     {
         return $this->additions;
     }
@@ -114,7 +118,7 @@ class TeaBeverage extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function setAdditions(\TYPO3\CMS\Extbase\Persistence\ObjectStorage $additions)
+    public function setAdditions(ObjectStorage $additions)
     {
         $this->additions = $additions;
     }
@@ -126,7 +130,7 @@ class TeaBeverage extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function addAddition(\OliverKlee\Tea\Domain\Model\Addition $addition)
+    public function addAddition(Addition $addition)
     {
         $this->additions->attach($addition);
     }
@@ -138,7 +142,7 @@ class TeaBeverage extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function removeAddition(\OliverKlee\Tea\Domain\Model\Addition $additionToRemove)
+    public function removeAddition(Addition $additionToRemove)
     {
         $this->additions->detach($additionToRemove);
     }
@@ -146,7 +150,7 @@ class TeaBeverage extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
     /**
      * @return \TYPO3\CMS\Extbase\Persistence\ObjectStorage<\OliverKlee\Tea\Domain\Model\Testimonial> $testimonials
      */
-    public function getTestimonials()
+    public function getTestimonials(): ObjectStorage
     {
         return $this->testimonials;
     }
@@ -156,7 +160,7 @@ class TeaBeverage extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function setTestimonials(\TYPO3\CMS\Extbase\Persistence\ObjectStorage $testimonials)
+    public function setTestimonials(ObjectStorage $testimonials)
     {
         $this->testimonials = $testimonials;
     }
@@ -168,7 +172,7 @@ class TeaBeverage extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function addTestimonial(\OliverKlee\Tea\Domain\Model\Testimonial $testimonial)
+    public function addTestimonial(Testimonial $testimonial)
     {
         $this->testimonials->attach($testimonial);
     }
@@ -180,7 +184,7 @@ class TeaBeverage extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function removeTestimonial(\OliverKlee\Tea\Domain\Model\Testimonial $testimonialToRemove)
+    public function removeTestimonial(Testimonial $testimonialToRemove)
     {
         $this->testimonials->detach($testimonialToRemove);
     }
diff --git a/Classes/Domain/Model/TeaType.php b/Classes/Domain/Model/TeaType.php
index 7fa041f..b682d86 100644
--- a/Classes/Domain/Model/TeaType.php
+++ b/Classes/Domain/Model/TeaType.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Domain\Model;
 
 /*
@@ -33,9 +35,9 @@ class TeaType extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
     protected $caffeinated = false;
 
     /**
-     * @return string $title
+     * @return string
      */
-    public function getTitle()
+    public function getTitle(): string
     {
         return $this->title;
     }
@@ -45,15 +47,15 @@ class TeaType extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function setTitle($title)
+    public function setTitle(string $title)
     {
         $this->title = $title;
     }
 
     /**
-     * @return bool $caffeinated
+     * @return bool
      */
-    public function getCaffeinated()
+    public function getCaffeinated(): bool
     {
         return $this->caffeinated;
     }
@@ -63,7 +65,7 @@ class TeaType extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function setCaffeinated($caffeinated)
+    public function setCaffeinated(bool $caffeinated)
     {
         $this->caffeinated = $caffeinated;
     }
@@ -71,7 +73,7 @@ class TeaType extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
     /**
      * @return bool
      */
-    public function isCaffeinated()
+    public function isCaffeinated(): bool
     {
         return $this->getCaffeinated();
     }
diff --git a/Classes/Domain/Model/Testimonial.php b/Classes/Domain/Model/Testimonial.php
index abf622c..17d9f34 100644
--- a/Classes/Domain/Model/Testimonial.php
+++ b/Classes/Domain/Model/Testimonial.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Domain\Model;
 
 /*
@@ -37,7 +39,7 @@ class Testimonial extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
     protected $text = '';
 
     /**
-     * @return \DateTime $dateOfPosting
+     * @return \DateTime|null
      */
     public function getDateOfPosting()
     {
@@ -49,7 +51,7 @@ class Testimonial extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function setDateOfPosting($dateOfPosting)
+    public function setDateOfPosting(\DateTime $dateOfPosting)
     {
         $this->dateOfPosting = $dateOfPosting;
     }
@@ -57,7 +59,7 @@ class Testimonial extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
     /**
      * @return int $numberOfConsumedCups
      */
-    public function getNumberOfConsumedCups()
+    public function getNumberOfConsumedCups(): int
     {
         return $this->numberOfConsumedCups;
     }
@@ -67,15 +69,15 @@ class Testimonial extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function setNumberOfConsumedCups($numberOfConsumedCups)
+    public function setNumberOfConsumedCups(int $numberOfConsumedCups)
     {
         $this->numberOfConsumedCups = $numberOfConsumedCups;
     }
 
     /**
-     * @return string $text
+     * @return string
      */
-    public function getText()
+    public function getText(): string
     {
         return $this->text;
     }
@@ -85,7 +87,7 @@ class Testimonial extends \TYPO3\CMS\Extbase\DomainObject\AbstractEntity
      *
      * @return void
      */
-    public function setText($text)
+    public function setText(string $text)
     {
         $this->text = $text;
     }
diff --git a/Classes/Domain/Repository/TeaBeverageRepository.php b/Classes/Domain/Repository/TeaBeverageRepository.php
index d4d7002..0d2a2b6 100644
--- a/Classes/Domain/Repository/TeaBeverageRepository.php
+++ b/Classes/Domain/Repository/TeaBeverageRepository.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Domain\Repository;
 
 /*
diff --git a/Classes/Domain/Repository/TestimonialRepository.php b/Classes/Domain/Repository/TestimonialRepository.php
index 3712baf..ed2cc5b 100644
--- a/Classes/Domain/Repository/TestimonialRepository.php
+++ b/Classes/Domain/Repository/TestimonialRepository.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Domain\Repository;
 
 /*
diff --git a/Classes/Utility/FileUtility.php b/Classes/Utility/FileUtility.php
index aef54a8..27c0f53 100644
--- a/Classes/Utility/FileUtility.php
+++ b/Classes/Utility/FileUtility.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Utility;
 
 /*
@@ -31,7 +33,7 @@ class FileUtility
      *
      * @throws \InvalidArgumentException
      */
-    public function concatenate($targetFilePath, array $sourceFilePaths)
+    public function concatenate(string $targetFilePath, array $sourceFilePaths)
     {
         if ($targetFilePath === '') {
             throw new \InvalidArgumentException('$targetFileName must not be empty.', 1445631384);
diff --git a/Tests/Functional/Domain/Repository/TeaBeverageRepositoryTest.php b/Tests/Functional/Domain/Repository/TeaBeverageRepositoryTest.php
index 0088905..9650cf6 100644
--- a/Tests/Functional/Domain/Repository/TeaBeverageRepositoryTest.php
+++ b/Tests/Functional/Domain/Repository/TeaBeverageRepositoryTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Tests\Functional\Domain\Repository;
 
 /*
diff --git a/Tests/Functional/Domain/Repository/TestimonialRepositoryTest.php b/Tests/Functional/Domain/Repository/TestimonialRepositoryTest.php
index 6e4d5e8..c4772d7 100644
--- a/Tests/Functional/Domain/Repository/TestimonialRepositoryTest.php
+++ b/Tests/Functional/Domain/Repository/TestimonialRepositoryTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Tests\Functional\Domain\Repository;
 
 /*
diff --git a/Tests/Functional/Utility/FileUtilityTest.php b/Tests/Functional/Utility/FileUtilityTest.php
index 968f87d..7fddd56 100644
--- a/Tests/Functional/Utility/FileUtilityTest.php
+++ b/Tests/Functional/Utility/FileUtilityTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Tests\Functional\Utility;
 
 /*
diff --git a/Tests/Unit/Controller/TestimonialControllerTest.php b/Tests/Unit/Controller/TestimonialControllerTest.php
index 0e3e67b..52a1609 100644
--- a/Tests/Unit/Controller/TestimonialControllerTest.php
+++ b/Tests/Unit/Controller/TestimonialControllerTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Tests\Unit\Controller;
 
 /*
diff --git a/Tests/Unit/Domain/Model/AdditionTest.php b/Tests/Unit/Domain/Model/AdditionTest.php
index e01867d..eb891df 100644
--- a/Tests/Unit/Domain/Model/AdditionTest.php
+++ b/Tests/Unit/Domain/Model/AdditionTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Tests\Unit\Domain\Model;
 
 /*
diff --git a/Tests/Unit/Domain/Model/TeaBeverageTest.php b/Tests/Unit/Domain/Model/TeaBeverageTest.php
index d519017..1409b39 100644
--- a/Tests/Unit/Domain/Model/TeaBeverageTest.php
+++ b/Tests/Unit/Domain/Model/TeaBeverageTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Tests\Unit\Domain\Model;
 
 /*
diff --git a/Tests/Unit/Domain/Model/TeaTypeTest.php b/Tests/Unit/Domain/Model/TeaTypeTest.php
index 0f8cede..dba6b53 100644
--- a/Tests/Unit/Domain/Model/TeaTypeTest.php
+++ b/Tests/Unit/Domain/Model/TeaTypeTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Tests\Unit\Domain\Model;
 
 /*
diff --git a/Tests/Unit/Domain/Model/TestimonialTest.php b/Tests/Unit/Domain/Model/TestimonialTest.php
index 53e72b0..01241dc 100644
--- a/Tests/Unit/Domain/Model/TestimonialTest.php
+++ b/Tests/Unit/Domain/Model/TestimonialTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Tests\Unit\Domain\Model;
 
 /*
diff --git a/Tests/Unit/Domain/Repository/TeaBeverageRepositoryTest.php b/Tests/Unit/Domain/Repository/TeaBeverageRepositoryTest.php
index 992ac70..5353a60 100644
--- a/Tests/Unit/Domain/Repository/TeaBeverageRepositoryTest.php
+++ b/Tests/Unit/Domain/Repository/TeaBeverageRepositoryTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Tests\Unit\Domain\Repository;
 
 /*
diff --git a/Tests/Unit/Domain/Repository/TestimonialRepositoryTest.php b/Tests/Unit/Domain/Repository/TestimonialRepositoryTest.php
index da1ff49..b1729da 100644
--- a/Tests/Unit/Domain/Repository/TestimonialRepositoryTest.php
+++ b/Tests/Unit/Domain/Repository/TestimonialRepositoryTest.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 namespace OliverKlee\Tea\Tests\Unit\Domain\Repository;
 
 /*