diff --git a/.circleci/config.yml b/.circleci/config.yml
index 987538d..23e90f5 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -24,54 +24,6 @@ tests_with_future_mode: &tests_with_future_mode
       vendor/bin/php-cs-fixer fix --diff || (echo "Coding standards are not respected. Run 'vendor/bin/php-cs-fixer fix'" && exit 1)
 
 jobs:
-  php 5.6:
-    docker:
-      - image: circleci/php:5.6
-    steps:
-      - checkout
-      - <<: *composer
-      - <<: *tests
-
-  php 5.6 with future mode:
-    docker:
-      - image: circleci/php:5.6
-    steps:
-      - checkout
-      - <<: *composer
-      - <<: *tests
-
-  php 5.6 with lowest dependencies:
-    docker:
-      - image: circleci/php:5.6
-    steps:
-      - checkout
-      - <<: *composer_with_lowest_dependencies
-      - <<: *tests
-
-  php 7.0:
-    docker:
-      - image: circleci/php:7.0
-    steps:
-      - checkout
-      - <<: *composer
-      - <<: *tests
-
-  php 7.0 with future mode:
-    docker:
-      - image: circleci/php:7.0
-    steps:
-      - checkout
-      - <<: *composer
-      - <<: *tests_with_future_mode
-
-  php 7.0 with lowest dependencies:
-    docker:
-      - image: circleci/php:7.0
-    steps:
-      - checkout
-      - <<: *composer_with_lowest_dependencies
-      - <<: *tests
-
   php 7.1:
     docker:
       - image: circleci/php:7.1
@@ -166,20 +118,6 @@ workflows:
   PR:
     jobs:
       - documentation is up to date
-      - php 5.6
-      - php 5.6 with future mode:
-          requires:
-            - php 5.6
-      - php 5.6 with lowest dependencies:
-          requires:
-            - php 5.6
-      - php 7.0
-      - php 7.0 with future mode:
-          requires:
-            - php 7.0
-      - php 7.0 with lowest dependencies:
-          requires:
-            - php 7.0
       - php 7.1
       - php 7.1 with future mode:
           requires:
@@ -204,12 +142,6 @@ workflows:
       - release:
           requires:
             - documentation is up to date
-            - php 5.6
-            - php 5.6 with future mode
-            - php 5.6 with lowest dependencies
-            - php 7.0
-            - php 7.0 with future mode
-            - php 7.0 with lowest dependencies
             - php 7.1
             - php 7.1 with future mode
             - php 7.1 with lowest dependencies
diff --git a/.php_cs.dist b/.php_cs.dist
index 92a6471..f233da8 100644
--- a/.php_cs.dist
+++ b/.php_cs.dist
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use PedroTroller\CS\Fixer\Fixers;
 use PedroTroller\CS\Fixer\RuleSetFactory;
 
@@ -8,7 +10,7 @@ return PhpCsFixer\Config::create()
     ->setRules(
         RuleSetFactory::create()
             ->phpCsFixer(true)
-            ->php(5.6, true)
+            ->php(7.1, true)
             ->pedrotroller(true)
             ->enable('ordered_imports')
             ->enable('align_multiline_comment')
diff --git a/composer.json b/composer.json
index 4732f68..bd0fac9 100644
--- a/composer.json
+++ b/composer.json
@@ -3,7 +3,7 @@
     "description": "PHP-CS-FIXER : my custom fixers",
     "license": "MIT",
     "require": {
-        "php": ">=5.6",
+        "php": ">=7.1",
         "friendsofphp/php-cs-fixer": "^2.14.2"
     },
     "require-dev": {
diff --git a/spec/PedroTroller/CS/Fixer/RuleSetFactorySpec.php b/spec/PedroTroller/CS/Fixer/RuleSetFactorySpec.php
index 60e9557..3627294 100644
--- a/spec/PedroTroller/CS/Fixer/RuleSetFactorySpec.php
+++ b/spec/PedroTroller/CS/Fixer/RuleSetFactorySpec.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace spec\PedroTroller\CS\Fixer;
 
 use PedroTroller\CS\Fixer\Fixers;
diff --git a/src/PedroTroller/CS/Fixer/AbstractFixer.php b/src/PedroTroller/CS/Fixer/AbstractFixer.php
index 4e454e3..f27798d 100644
--- a/src/PedroTroller/CS/Fixer/AbstractFixer.php
+++ b/src/PedroTroller/CS/Fixer/AbstractFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer;
 
 use PhpCsFixer\AbstractFixer as PhpCsFixer;
diff --git a/src/PedroTroller/CS/Fixer/AbstractOrderedClassElementsFixer.php b/src/PedroTroller/CS/Fixer/AbstractOrderedClassElementsFixer.php
index 52c60c4..1a94eeb 100644
--- a/src/PedroTroller/CS/Fixer/AbstractOrderedClassElementsFixer.php
+++ b/src/PedroTroller/CS/Fixer/AbstractOrderedClassElementsFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer;
 
 use PhpCsFixer\Tokenizer\CT;
@@ -11,7 +13,7 @@ abstract class AbstractOrderedClassElementsFixer extends AbstractFixer
     /**
      * {@inheritdoc}
      */
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         for ($i = 1, $count = $tokens->count(); $i < $count; ++$i) {
             if (!$tokens[$i]->isClassy()) {
@@ -187,7 +189,7 @@ private function sortTokens(
         $startIndex,
         $endIndex,
         array $elements
-    ) {
+    ): void {
         $replaceTokens = [];
 
         foreach ($elements as $element) {
diff --git a/src/PedroTroller/CS/Fixer/ClassNotation/OrderedWithGetterAndSetterFirstFixer.php b/src/PedroTroller/CS/Fixer/ClassNotation/OrderedWithGetterAndSetterFirstFixer.php
index 173ee3b..058f70d 100644
--- a/src/PedroTroller/CS/Fixer/ClassNotation/OrderedWithGetterAndSetterFirstFixer.php
+++ b/src/PedroTroller/CS/Fixer/ClassNotation/OrderedWithGetterAndSetterFirstFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer\ClassNotation;
 
 use PedroTroller\CS\Fixer\AbstractOrderedClassElementsFixer;
diff --git a/src/PedroTroller/CS/Fixer/CodingStyle/ExceptionsPunctuationFixer.php b/src/PedroTroller/CS/Fixer/CodingStyle/ExceptionsPunctuationFixer.php
index 7493adc..12dee50 100644
--- a/src/PedroTroller/CS/Fixer/CodingStyle/ExceptionsPunctuationFixer.php
+++ b/src/PedroTroller/CS/Fixer/CodingStyle/ExceptionsPunctuationFixer.php
@@ -59,7 +59,7 @@ public function getDocumentation()
         return 'Exception messages MUST ends by ".", "…", "?" or "!".<br /><br /><i>Risky: will change the exception message.</i>';
     }
 
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         $cases = $this->analyze($tokens)->findAllSequences([
             [
diff --git a/src/PedroTroller/CS/Fixer/CodingStyle/ForbiddenFunctionsFixer.php b/src/PedroTroller/CS/Fixer/CodingStyle/ForbiddenFunctionsFixer.php
index 22005dc..48db2f0 100644
--- a/src/PedroTroller/CS/Fixer/CodingStyle/ForbiddenFunctionsFixer.php
+++ b/src/PedroTroller/CS/Fixer/CodingStyle/ForbiddenFunctionsFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer\CodingStyle;
 
 use PedroTroller\CS\Fixer\AbstractFixer;
@@ -59,7 +61,7 @@ public function getDocumentation()
         return 'Forbidden functions MUST BE commented';
     }
 
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         $calls = [];
 
diff --git a/src/PedroTroller/CS/Fixer/CodingStyle/LineBreakBetweenMethodArgumentsFixer.php b/src/PedroTroller/CS/Fixer/CodingStyle/LineBreakBetweenMethodArgumentsFixer.php
index 9062561..2b8c6a9 100644
--- a/src/PedroTroller/CS/Fixer/CodingStyle/LineBreakBetweenMethodArgumentsFixer.php
+++ b/src/PedroTroller/CS/Fixer/CodingStyle/LineBreakBetweenMethodArgumentsFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer\CodingStyle;
 
 use PedroTroller\CS\Fixer\AbstractFixer;
@@ -82,7 +84,7 @@ public function fun3(
     /**
      * {@inheritdoc}
      */
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         $functions = [];
 
@@ -158,7 +160,7 @@ protected function createConfigurationDefinition()
         ]);
     }
 
-    private function splitArgs(Tokens $tokens, $index)
+    private function splitArgs(Tokens $tokens, $index): void
     {
         $openBraceIndex  = $tokens->getNextTokenOfKind($index, ['(']);
         $closeBraceIndex = $this->analyze($tokens)->getClosingParenthesis($openBraceIndex);
@@ -220,7 +222,7 @@ private function splitArgs(Tokens $tokens, $index)
         $tokens->removeTrailingWhitespace($tokens->getPrevMeaningfulToken($closeBraceIndex));
     }
 
-    private function mergeArgs(Tokens $tokens, $index)
+    private function mergeArgs(Tokens $tokens, $index): void
     {
         $openBraceIndex  = $tokens->getNextTokenOfKind($index, ['(']);
         $closeBraceIndex = $this->analyze($tokens)->getClosingParenthesis($openBraceIndex);
diff --git a/src/PedroTroller/CS/Fixer/CodingStyle/LineBreakBetweenStatementsFixer.php b/src/PedroTroller/CS/Fixer/CodingStyle/LineBreakBetweenStatementsFixer.php
index dd7dd21..91d0ea5 100644
--- a/src/PedroTroller/CS/Fixer/CodingStyle/LineBreakBetweenStatementsFixer.php
+++ b/src/PedroTroller/CS/Fixer/CodingStyle/LineBreakBetweenStatementsFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer\CodingStyle;
 
 use PedroTroller\CS\Fixer\AbstractFixer;
@@ -64,14 +66,14 @@ public function getDocumentation()
         return 'Transform multiline docblocks with only one comment into a singleline docblock.';
     }
 
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         foreach ($tokens->findGivenKind(array_keys($this->handlers)) as $kind => $matchedTokens) {
             $this->{'handle'.ucfirst($this->handlers[$kind])}($matchedTokens, $tokens);
         }
     }
 
-    private function handleDo(array $matchedTokens, Tokens $tokens)
+    private function handleDo(array $matchedTokens, Tokens $tokens): void
     {
         foreach ($matchedTokens as $index => $token) {
             $this->fixSpaces(
@@ -81,7 +83,7 @@ private function handleDo(array $matchedTokens, Tokens $tokens)
         }
     }
 
-    private function handleCommon(array $matchedTokens, Tokens $tokens)
+    private function handleCommon(array $matchedTokens, Tokens $tokens): void
     {
         foreach ($matchedTokens as $index => $token) {
             $curlyBracket = $tokens->findSequence([
@@ -111,7 +113,7 @@ private function handleCommon(array $matchedTokens, Tokens $tokens)
         }
     }
 
-    private function fixSpaces($index, Tokens $tokens)
+    private function fixSpaces($index, Tokens $tokens): void
     {
         $space = $index + 1;
 
diff --git a/src/PedroTroller/CS/Fixer/Comment/CommentLineToPhpdocBlockFixer.php b/src/PedroTroller/CS/Fixer/Comment/CommentLineToPhpdocBlockFixer.php
index cc27d38..4e126d3 100644
--- a/src/PedroTroller/CS/Fixer/Comment/CommentLineToPhpdocBlockFixer.php
+++ b/src/PedroTroller/CS/Fixer/Comment/CommentLineToPhpdocBlockFixer.php
@@ -85,7 +85,7 @@ public function getPriority()
     /**
      * {@inheritdoc}
      */
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         $elements = $this->analyze($tokens)->getClassyElements();
 
diff --git a/src/PedroTroller/CS/Fixer/Comment/SingleLineCommentFixer.php b/src/PedroTroller/CS/Fixer/Comment/SingleLineCommentFixer.php
index 444cca6..610693f 100644
--- a/src/PedroTroller/CS/Fixer/Comment/SingleLineCommentFixer.php
+++ b/src/PedroTroller/CS/Fixer/Comment/SingleLineCommentFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer\Comment;
 
 use PedroTroller\CS\Fixer\AbstractFixer;
@@ -96,7 +98,7 @@ public function getDeprecationReplacement()
     /**
      * {@inheritdoc}
      */
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         $this->{$this->configuration['action'].'Comment'}($tokens);
     }
@@ -117,7 +119,7 @@ protected function createConfigurationDefinition()
         ]);
     }
 
-    private function expandedComment(Tokens $tokens)
+    private function expandedComment(Tokens $tokens): void
     {
         foreach ($this->getComments($tokens) as $index => $token) {
             $space = '';
@@ -135,7 +137,7 @@ private function expandedComment(Tokens $tokens)
         }
     }
 
-    private function collapsedComment(Tokens $tokens)
+    private function collapsedComment(Tokens $tokens): void
     {
         foreach ($this->getComments($tokens) as $index => $token) {
             foreach ($this->configuration['types'] as $variable) {
diff --git a/src/PedroTroller/CS/Fixer/Comment/UselessCommentFixer.php b/src/PedroTroller/CS/Fixer/Comment/UselessCommentFixer.php
index 286f85e..955a480 100644
--- a/src/PedroTroller/CS/Fixer/Comment/UselessCommentFixer.php
+++ b/src/PedroTroller/CS/Fixer/Comment/UselessCommentFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer\Comment;
 
 use PedroTroller\CS\Fixer\AbstractFixer;
@@ -78,7 +80,7 @@ public function getDeprecationReplacement()
     /**
      * {@inheritdoc}
      */
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         foreach ($this->analyze($tokens)->getClassyElements() as $index => $element) {
             if ('method' !== $element['type']) {
diff --git a/src/PedroTroller/CS/Fixer/DeadCode/UselessCodeAfterReturnFixer.php b/src/PedroTroller/CS/Fixer/DeadCode/UselessCodeAfterReturnFixer.php
index 849b0e3..622abfe 100644
--- a/src/PedroTroller/CS/Fixer/DeadCode/UselessCodeAfterReturnFixer.php
+++ b/src/PedroTroller/CS/Fixer/DeadCode/UselessCodeAfterReturnFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer\DeadCode;
 
 use PedroTroller\CS\Fixer\AbstractFixer;
@@ -72,7 +74,7 @@ public function buildCallable()
     /**
      * {@inheritdoc}
      */
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         $returns  = $tokens->findGivenKind(T_RETURN);
         $analyzer = $this->analyze($tokens);
diff --git a/src/PedroTroller/CS/Fixer/DoctrineMigrationsFixer.php b/src/PedroTroller/CS/Fixer/DoctrineMigrationsFixer.php
index fb2ec92..4e402b9 100644
--- a/src/PedroTroller/CS/Fixer/DoctrineMigrationsFixer.php
+++ b/src/PedroTroller/CS/Fixer/DoctrineMigrationsFixer.php
@@ -111,13 +111,13 @@ protected function createConfigurationDefinition()
     /**
      * {@inheritdoc}
      */
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         $this->removeUselessGetDocumentation($tokens);
         $this->removeUselessComments($tokens);
     }
 
-    private function removeUselessGetDocumentation(Tokens $tokens)
+    private function removeUselessGetDocumentation(Tokens $tokens): void
     {
         foreach ($this->analyze($tokens)->getElements() as $element) {
             if ('method' !== $element['type']) {
@@ -157,7 +157,7 @@ private function removeUselessGetDocumentation(Tokens $tokens)
         }
     }
 
-    private function removeUselessComments(Tokens $tokens)
+    private function removeUselessComments(Tokens $tokens): void
     {
         $comments = $this->getComments($tokens);
 
diff --git a/src/PedroTroller/CS/Fixer/Fixers.php b/src/PedroTroller/CS/Fixer/Fixers.php
index 632d74e..19b524a 100644
--- a/src/PedroTroller/CS/Fixer/Fixers.php
+++ b/src/PedroTroller/CS/Fixer/Fixers.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer;
 
 use IteratorAggregate;
diff --git a/src/PedroTroller/CS/Fixer/Phpspec/OrderedSpecElementsFixer.php b/src/PedroTroller/CS/Fixer/Phpspec/OrderedSpecElementsFixer.php
index 434cbb3..83eaf85 100644
--- a/src/PedroTroller/CS/Fixer/Phpspec/OrderedSpecElementsFixer.php
+++ b/src/PedroTroller/CS/Fixer/Phpspec/OrderedSpecElementsFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer\Phpspec;
 
 use PedroTroller\CS\Fixer\AbstractOrderedClassElementsFixer;
diff --git a/src/PedroTroller/CS/Fixer/Phpspec/PhpspecScenarioReturnTypeDeclarationFixer.php b/src/PedroTroller/CS/Fixer/Phpspec/PhpspecScenarioReturnTypeDeclarationFixer.php
index a8783da..96fce47 100644
--- a/src/PedroTroller/CS/Fixer/Phpspec/PhpspecScenarioReturnTypeDeclarationFixer.php
+++ b/src/PedroTroller/CS/Fixer/Phpspec/PhpspecScenarioReturnTypeDeclarationFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer\Phpspec;
 
 use PedroTroller\CS\Fixer\AbstractFixer;
@@ -92,7 +94,7 @@ public function getPriority()
     /**
      * {@inheritdoc}
      */
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         foreach ($tokens as $index => $token) {
             if (T_FUNCTION !== $token->getId()) {
diff --git a/src/PedroTroller/CS/Fixer/Phpspec/PhpspecScenarioScopeFixer.php b/src/PedroTroller/CS/Fixer/Phpspec/PhpspecScenarioScopeFixer.php
index 02af338..1aeeaca 100644
--- a/src/PedroTroller/CS/Fixer/Phpspec/PhpspecScenarioScopeFixer.php
+++ b/src/PedroTroller/CS/Fixer/Phpspec/PhpspecScenarioScopeFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer\Phpspec;
 
 use PedroTroller\CS\Fixer\AbstractFixer;
@@ -92,7 +94,7 @@ public function getPriority()
     /**
      * {@inheritdoc}
      */
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         foreach ($tokens as $index => $token) {
             if (T_FUNCTION !== $token->getId()) {
diff --git a/src/PedroTroller/CS/Fixer/PhpspecFixer.php b/src/PedroTroller/CS/Fixer/PhpspecFixer.php
index 1d854a9..453940b 100644
--- a/src/PedroTroller/CS/Fixer/PhpspecFixer.php
+++ b/src/PedroTroller/CS/Fixer/PhpspecFixer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer;
 
 use PhpCsFixer\Fixer\ClassNotation\VisibilityRequiredFixer;
@@ -138,7 +140,7 @@ protected function sortElements(array $elements)
         return $ordered;
     }
 
-    protected function applyFix(SplFileInfo $file, Tokens $tokens)
+    protected function applyFix(SplFileInfo $file, Tokens $tokens): void
     {
         $this->removeScope($file, $tokens);
         $this->removeReturn($file, $tokens);
@@ -146,7 +148,7 @@ protected function applyFix(SplFileInfo $file, Tokens $tokens)
         parent::applyFix($file, $tokens);
     }
 
-    private function removeScope(SplFileInfo $file, Tokens $tokens)
+    private function removeScope(SplFileInfo $file, Tokens $tokens): void
     {
         foreach ($tokens as $index => $token) {
             if (T_FUNCTION !== $token->getId()) {
@@ -177,7 +179,7 @@ private function removeScope(SplFileInfo $file, Tokens $tokens)
         }
     }
 
-    private function removeReturn(SplFileInfo $file, Tokens $tokens)
+    private function removeReturn(SplFileInfo $file, Tokens $tokens): void
     {
         foreach ($tokens as $index => $token) {
             if (T_FUNCTION !== $token->getId()) {
diff --git a/src/PedroTroller/CS/Fixer/Priority.php b/src/PedroTroller/CS/Fixer/Priority.php
index fe5a1ac..4cd2b12 100644
--- a/src/PedroTroller/CS/Fixer/Priority.php
+++ b/src/PedroTroller/CS/Fixer/Priority.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer;
 
 final class Priority
diff --git a/src/PedroTroller/CS/Fixer/RuleSetFactory.php b/src/PedroTroller/CS/Fixer/RuleSetFactory.php
index d5cc4fb..1f33513 100644
--- a/src/PedroTroller/CS/Fixer/RuleSetFactory.php
+++ b/src/PedroTroller/CS/Fixer/RuleSetFactory.php
@@ -243,19 +243,19 @@ private function migration($package, $version, $risky)
         $rules = array_filter($rules);
 
         $rules = array_filter($rules, function ($versionAndRisky) use ($package) {
-            list($rule, $rulePackage, $ruleVersion, $ruleRisky) = $versionAndRisky;
+            [$rule, $rulePackage, $ruleVersion, $ruleRisky] = $versionAndRisky;
 
             return strtoupper($package) === strtoupper($rulePackage);
         });
 
         $rules = array_filter($rules, function ($versionAndRisky) use ($version) {
-            list($rule, $rulePackage, $ruleVersion, $ruleRisky) = $versionAndRisky;
+            [$rule, $rulePackage, $ruleVersion, $ruleRisky] = $versionAndRisky;
 
             return ((float) $ruleVersion / 10) <= $version;
         });
 
         $rules = array_filter($rules, function ($versionAndRisky) use ($risky) {
-            list($rule, $rulePackage, $ruleVersion, $ruleRisky) = $versionAndRisky;
+            [$rule, $rulePackage, $ruleVersion, $ruleRisky] = $versionAndRisky;
 
             if ($risky) {
                 return true;
diff --git a/src/PedroTroller/CS/Fixer/TokenSignatures.php b/src/PedroTroller/CS/Fixer/TokenSignatures.php
index 6b094ed..57b5d19 100644
--- a/src/PedroTroller/CS/Fixer/TokenSignatures.php
+++ b/src/PedroTroller/CS/Fixer/TokenSignatures.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer;
 
 final class TokenSignatures
diff --git a/src/PedroTroller/CS/Fixer/TokensAnalyzer.php b/src/PedroTroller/CS/Fixer/TokensAnalyzer.php
index 5b6970d..d12f062 100644
--- a/src/PedroTroller/CS/Fixer/TokensAnalyzer.php
+++ b/src/PedroTroller/CS/Fixer/TokensAnalyzer.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace PedroTroller\CS\Fixer;
 
 use Exception;
@@ -411,7 +413,7 @@ public function isInsideSwitchCase($index)
         }
 
         foreach ($intervals as $interval) {
-            list($start, $end) = $interval;
+            [$start, $end] = $interval;
 
             if ($index >= $start && $index <= $end) {
                 return true;
diff --git a/tests/Orchestra.php b/tests/Orchestra.php
index 339c9ec..7a79bba 100644
--- a/tests/Orchestra.php
+++ b/tests/Orchestra.php
@@ -27,7 +27,7 @@ private function __construct(FixerInterface $fixer)
         $this->fixer = $fixer;
     }
 
-    public static function run()
+    public static function run(): void
     {
         self::assert(new OrderedWithGetterAndSetterFirstFixer())
             ->before(new OrderedClassElementsFixer())
diff --git a/tests/Runner.php b/tests/Runner.php
index c6523bd..429c189 100644
--- a/tests/Runner.php
+++ b/tests/Runner.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests;
 
 use Exception;
@@ -11,12 +13,12 @@
 
 class Runner
 {
-    public static function run()
+    public static function run(): void
     {
         $deprecations = [];
 
         set_error_handler(
-            function ($type, $message, $file, $line) use (&$deprecations) {
+            function ($type, $message, $file, $line) use (&$deprecations): void {
                 $deprecations[$message][] = sprintf('%s at line %d', $file, $line);
                 $deprecations[$message] = array_unique($deprecations[$message]);
 
@@ -51,7 +53,7 @@ function ($message, array $files) {
         }
     }
 
-    private static function runUseCases()
+    private static function runUseCases(): void
     {
         $directory = sprintf('%s/UseCase', __DIR__);
 
@@ -96,7 +98,7 @@ private static function runUseCases()
         }
     }
 
-    private static function runAnalyzerIntegrations()
+    private static function runAnalyzerIntegrations(): void
     {
         $directory = sprintf('%s/TokensAnalyzerIntegration', __DIR__);
 
diff --git a/tests/TokensAnalyzerIntegration.php b/tests/TokensAnalyzerIntegration.php
index 5b8a55c..0423e15 100644
--- a/tests/TokensAnalyzerIntegration.php
+++ b/tests/TokensAnalyzerIntegration.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests;
 
 use Exception;
diff --git a/tests/TokensAnalyzerIntegration/InSwitch.php b/tests/TokensAnalyzerIntegration/InSwitch.php
index afe4e88..bb9cfc2 100644
--- a/tests/TokensAnalyzerIntegration/InSwitch.php
+++ b/tests/TokensAnalyzerIntegration/InSwitch.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\TokensAnalyzerIntegration;
 
 use PedroTroller\CS\Fixer\TokensAnalyzer;
@@ -37,7 +39,7 @@ public function theFunction()
     /**
      * {@inheritdoc}
      */
-    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens)
+    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens): void
     {
         Assert::false(
             $analyzer->isInsideSwitchCase(
diff --git a/tests/TokensAnalyzerIntegration/LineIndentation.php b/tests/TokensAnalyzerIntegration/LineIndentation.php
index 81aa909..b66ae3c 100644
--- a/tests/TokensAnalyzerIntegration/LineIndentation.php
+++ b/tests/TokensAnalyzerIntegration/LineIndentation.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\TokensAnalyzerIntegration;
 
 use PedroTroller\CS\Fixer\TokensAnalyzer;
@@ -37,7 +39,7 @@ public function theFunction()
     /**
      * {@inheritdoc}
      */
-    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens)
+    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens): void
     {
         Assert::eq(
             $analyzer->getLineIndentation(
diff --git a/tests/TokensAnalyzerIntegration/MethodArguments.php b/tests/TokensAnalyzerIntegration/MethodArguments.php
index 7c14c1d..e1b1bd1 100644
--- a/tests/TokensAnalyzerIntegration/MethodArguments.php
+++ b/tests/TokensAnalyzerIntegration/MethodArguments.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\TokensAnalyzerIntegration;
 
 use PedroTroller\CS\Fixer\TokensAnalyzer;
@@ -43,7 +45,7 @@ public function setUser($user)
     /**
      * {@inheritdoc}
      */
-    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens)
+    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens): void
     {
         $methods = array_filter(
             $analyzer->getClassyElements(),
@@ -52,7 +54,7 @@ function ($element) { return 'method' === $element['type']; }
 
         Assert::count($methods, 3);
 
-        list($contructor, $theFunction, $setUser) = array_keys($methods);
+        [$contructor, $theFunction, $setUser] = array_keys($methods);
 
         $arguments = $analyzer->getMethodArguments($contructor);
         Assert::eq($analyzer->getNumberOfArguments($contructor), 0);
diff --git a/tests/TokensAnalyzerIntegration/NextSemiColon.php b/tests/TokensAnalyzerIntegration/NextSemiColon.php
index 1414312..e954984 100644
--- a/tests/TokensAnalyzerIntegration/NextSemiColon.php
+++ b/tests/TokensAnalyzerIntegration/NextSemiColon.php
@@ -48,7 +48,7 @@ public function theFunction()
     /**
      * {@inheritdoc}
      */
-    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens)
+    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens): void
     {
         Assert::eq(
             $analyzer->getNextSemiColon(
diff --git a/tests/TokensAnalyzerIntegration/Parenthesis.php b/tests/TokensAnalyzerIntegration/Parenthesis.php
index 6647383..2f76274 100644
--- a/tests/TokensAnalyzerIntegration/Parenthesis.php
+++ b/tests/TokensAnalyzerIntegration/Parenthesis.php
@@ -45,7 +45,7 @@ public function setName(string $name): void
 PHP;
     }
 
-    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens)
+    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens): void
     {
         Assert::eq(
             $analyzer->getClosingParenthesis($this->tokenContaining($tokens, 'getId') + 1),
diff --git a/tests/TokensAnalyzerIntegration/ReturnedType.php b/tests/TokensAnalyzerIntegration/ReturnedType.php
index ebdb4a7..2f9fe94 100644
--- a/tests/TokensAnalyzerIntegration/ReturnedType.php
+++ b/tests/TokensAnalyzerIntegration/ReturnedType.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\TokensAnalyzerIntegration;
 
 use PedroTroller\CS\Fixer\TokensAnalyzer;
@@ -49,7 +51,7 @@ public function setName(string $name): void
     /**
      * {@inheritdoc}
      */
-    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens)
+    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens): void
     {
         Assert::eq(
             $analyzer->getReturnedType(
diff --git a/tests/TokensAnalyzerIntegration/SizeOfTheLine.php b/tests/TokensAnalyzerIntegration/SizeOfTheLine.php
index 75f4a9f..975d84c 100644
--- a/tests/TokensAnalyzerIntegration/SizeOfTheLine.php
+++ b/tests/TokensAnalyzerIntegration/SizeOfTheLine.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\TokensAnalyzerIntegration;
 
 use PedroTroller\CS\Fixer\TokensAnalyzer;
@@ -34,7 +36,7 @@ public function theFunction()
     /**
      * {@inheritdoc}
      */
-    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens)
+    public function assertions(TokensAnalyzer $analyzer, Tokens $tokens): void
     {
         Assert::eq(
             $analyzer->getSizeOfTheLine(
diff --git a/tests/UseCase.php b/tests/UseCase.php
index 1af4320..d961301 100644
--- a/tests/UseCase.php
+++ b/tests/UseCase.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests;
 
 use PhpCsFixer\Fixer\FixerInterface;
diff --git a/tests/UseCase/ForbiddenFunctions.php b/tests/UseCase/ForbiddenFunctions.php
index 3d57c54..6bb0e49 100644
--- a/tests/UseCase/ForbiddenFunctions.php
+++ b/tests/UseCase/ForbiddenFunctions.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase;
 
 use PedroTroller\CS\Fixer\CodingStyle\ForbiddenFunctionsFixer;
diff --git a/tests/UseCase/LineBreakBetweenMethods.php b/tests/UseCase/LineBreakBetweenMethods.php
index 188f9df..f18f829 100644
--- a/tests/UseCase/LineBreakBetweenMethods.php
+++ b/tests/UseCase/LineBreakBetweenMethods.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase;
 
 use PedroTroller\CS\Fixer\CodingStyle\LineBreakBetweenMethodArgumentsFixer;
diff --git a/tests/UseCase/LineBreakBetweenMethods/Regression/Case1.php b/tests/UseCase/LineBreakBetweenMethods/Regression/Case1.php
index e91f9d2..bf2211d 100644
--- a/tests/UseCase/LineBreakBetweenMethods/Regression/Case1.php
+++ b/tests/UseCase/LineBreakBetweenMethods/Regression/Case1.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase\LineBreakBetweenMethods\Regression;
 
 use PedroTroller\CS\Fixer\CodingStyle\LineBreakBetweenMethodArgumentsFixer;
diff --git a/tests/UseCase/LineBreakBetweenMethods/Regression/Case2.php b/tests/UseCase/LineBreakBetweenMethods/Regression/Case2.php
index af62eab..26d227a 100644
--- a/tests/UseCase/LineBreakBetweenMethods/Regression/Case2.php
+++ b/tests/UseCase/LineBreakBetweenMethods/Regression/Case2.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase\LineBreakBetweenMethods\Regression;
 
 use PedroTroller\CS\Fixer\CodingStyle\LineBreakBetweenMethodArgumentsFixer;
diff --git a/tests/UseCase/LineBreakBetweenMethods/Regression/Case3.php b/tests/UseCase/LineBreakBetweenMethods/Regression/Case3.php
index 5fe99dd..39f657e 100644
--- a/tests/UseCase/LineBreakBetweenMethods/Regression/Case3.php
+++ b/tests/UseCase/LineBreakBetweenMethods/Regression/Case3.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase\LineBreakBetweenMethods\Regression;
 
 use PedroTroller\CS\Fixer\CodingStyle\LineBreakBetweenMethodArgumentsFixer;
diff --git a/tests/UseCase/LineBreakBetweenMethodsWithNoReformatting.php b/tests/UseCase/LineBreakBetweenMethodsWithNoReformatting.php
index 71831ba..86b4716 100644
--- a/tests/UseCase/LineBreakBetweenMethodsWithNoReformatting.php
+++ b/tests/UseCase/LineBreakBetweenMethodsWithNoReformatting.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase;
 
 use PedroTroller\CS\Fixer\CodingStyle\LineBreakBetweenMethodArgumentsFixer;
diff --git a/tests/UseCase/LineBreakBetweenStatements.php b/tests/UseCase/LineBreakBetweenStatements.php
index e98b4a8..859a8b7 100644
--- a/tests/UseCase/LineBreakBetweenStatements.php
+++ b/tests/UseCase/LineBreakBetweenStatements.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase;
 
 use PedroTroller\CS\Fixer\CodingStyle\LineBreakBetweenStatementsFixer;
diff --git a/tests/UseCase/OrderedSpecElements.php b/tests/UseCase/OrderedSpecElements.php
index a9b7aa1..91a02e7 100644
--- a/tests/UseCase/OrderedSpecElements.php
+++ b/tests/UseCase/OrderedSpecElements.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase;
 
 use PedroTroller\CS\Fixer\Phpspec\OrderedSpecElementsFixer;
diff --git a/tests/UseCase/OrderedSpecElements/Regression/Case1.php b/tests/UseCase/OrderedSpecElements/Regression/Case1.php
index 60a3313..ec24ace 100644
--- a/tests/UseCase/OrderedSpecElements/Regression/Case1.php
+++ b/tests/UseCase/OrderedSpecElements/Regression/Case1.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase\OrderedSpecElements\Regression;
 
 use PedroTroller\CS\Fixer\Phpspec\OrderedSpecElementsFixer;
diff --git a/tests/UseCase/OrderedWithGetterAndSetterFirst.php b/tests/UseCase/OrderedWithGetterAndSetterFirst.php
index e384ca2..5e571c1 100644
--- a/tests/UseCase/OrderedWithGetterAndSetterFirst.php
+++ b/tests/UseCase/OrderedWithGetterAndSetterFirst.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase;
 
 use PedroTroller\CS\Fixer\ClassNotation\OrderedWithGetterAndSetterFirstFixer;
diff --git a/tests/UseCase/OrderedWithGetterAndSetterFirst/Regression/Case1.php b/tests/UseCase/OrderedWithGetterAndSetterFirst/Regression/Case1.php
index 6d664d6..7d22e57 100644
--- a/tests/UseCase/OrderedWithGetterAndSetterFirst/Regression/Case1.php
+++ b/tests/UseCase/OrderedWithGetterAndSetterFirst/Regression/Case1.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase\OrderedWithGetterAndSetterFirst\Regression;
 
 use PedroTroller\CS\Fixer\ClassNotation\OrderedWithGetterAndSetterFirstFixer;
diff --git a/tests/UseCase/OrderedWithGetterAndSetterFirst/Regression/Case2.php b/tests/UseCase/OrderedWithGetterAndSetterFirst/Regression/Case2.php
index 5da6024..36eebbf 100644
--- a/tests/UseCase/OrderedWithGetterAndSetterFirst/Regression/Case2.php
+++ b/tests/UseCase/OrderedWithGetterAndSetterFirst/Regression/Case2.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase\OrderedWithGetterAndSetterFirst\Regression;
 
 use PedroTroller\CS\Fixer\ClassNotation\OrderedWithGetterAndSetterFirstFixer;
diff --git a/tests/UseCase/Phpspec.php b/tests/UseCase/Phpspec.php
index 38c9e4b..7f5e8a0 100644
--- a/tests/UseCase/Phpspec.php
+++ b/tests/UseCase/Phpspec.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\Usecase;
 
 use PedroTroller\CS\Fixer\PhpspecFixer;
diff --git a/tests/UseCase/PhpspecScenarioScope.php b/tests/UseCase/PhpspecScenarioScope.php
index a012c42..127d80c 100644
--- a/tests/UseCase/PhpspecScenarioScope.php
+++ b/tests/UseCase/PhpspecScenarioScope.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\Usecase;
 
 use PedroTroller\CS\Fixer\Phpspec\PhpspecScenarioScopeFixer;
diff --git a/tests/UseCase/UselessCodeAfterReturn.php b/tests/UseCase/UselessCodeAfterReturn.php
index 16d376a..dd36b1f 100644
--- a/tests/UseCase/UselessCodeAfterReturn.php
+++ b/tests/UseCase/UselessCodeAfterReturn.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase;
 
 use PedroTroller\CS\Fixer\DeadCode\UselessCodeAfterReturnFixer;
diff --git a/tests/UseCase/UselessComment.php b/tests/UseCase/UselessComment.php
index cb7b785..0cb9d7e 100644
--- a/tests/UseCase/UselessComment.php
+++ b/tests/UseCase/UselessComment.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase;
 
 use PedroTroller\CS\Fixer\Comment\UselessCommentFixer;
diff --git a/tests/UseCase/UselessComment/Php71.php b/tests/UseCase/UselessComment/Php71.php
index 19acbfd..32a23cf 100644
--- a/tests/UseCase/UselessComment/Php71.php
+++ b/tests/UseCase/UselessComment/Php71.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase\UselessComment;
 
 use PedroTroller\CS\Fixer\Comment\UselessCommentFixer;
diff --git a/tests/UseCase/UselessComment/Regression/DoubleLineBreak.php b/tests/UseCase/UselessComment/Regression/DoubleLineBreak.php
index fa6e40f..04afc13 100644
--- a/tests/UseCase/UselessComment/Regression/DoubleLineBreak.php
+++ b/tests/UseCase/UselessComment/Regression/DoubleLineBreak.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace tests\UseCase\UselessComment\Regression;
 
 use PedroTroller\CS\Fixer\Comment\UselessCommentFixer;