diff --git a/.github/workflows/main.yaml b/.github/workflows/main.yaml
index 8dea16d..6f082d3 100644
--- a/.github/workflows/main.yaml
+++ b/.github/workflows/main.yaml
@@ -109,4 +109,4 @@ jobs:
         run: composer install --no-progress --prefer-dist --optimize-autoloader
 
       - name: Static analysis with PHPStan
-        run: ./vendor/bin/phpstan analyse -l 5
+        run: ./vendor/bin/phpstan analyse --ansi
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 7c17d43..82afaae 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -1,12 +1,16 @@
 parameters:
-    level: 5
+    level: 8
     paths:
         - src/
         - tests/
     parallel:
         processTimeout: 300.0
     checkMissingIterableValueType: false
+    checkGenericClassInNonGenericObjectType: false
     ignoreErrors:
         - message: '#Left side of && is always false.#'
           path: src/Blueprint/Components/Components.php
           count: 1
+        - message: '#Parameter $length of function file_get_contents expects int<0, max>|null, int|null given.#'
+          path: src/Parser/Utils/IOCapable.php
+          count: 4
diff --git a/src/Blueprint/Components/Components.php b/src/Blueprint/Components/Components.php
index ab28340..f0785c8 100644
--- a/src/Blueprint/Components/Components.php
+++ b/src/Blueprint/Components/Components.php
@@ -16,7 +16,7 @@ class Components implements ComponentInterface, Iterator
     private const MISSING_ELEMENT = 'Blueprint section %s is missing a mandatory element %s';
     private const INVALID_VALUE = 'Blueprint %s element has invalid value (%s). Acceptable value(s) [%s]';
 
-    private $position = 0;
+    private int $position = 0;
 
     /** @var Component[] */
     public readonly array $components;
diff --git a/src/Blueprint/Components/Conditions.php b/src/Blueprint/Components/Conditions.php
index 1720cda..5b65ff5 100644
--- a/src/Blueprint/Components/Conditions.php
+++ b/src/Blueprint/Components/Conditions.php
@@ -25,7 +25,7 @@ public function __construct(
         $this->position = 0;
     }
 
-    protected function buildConditions($conditions): array
+    protected function buildConditions(array $conditions): array
     {
         $objectConditions = [];
         foreach ($conditions as $condition) {
@@ -75,9 +75,6 @@ public static function validation(array &$conditions): void
 
             $case = self::getConditionKeyword($condition);
 
-            if ($case === false) {
-                throw new InvalidFieldException('no valid condition found');
-            }
             $finalConditions[] = [
                 'column' => $condition['column'],
                 'keyword' => $case,
@@ -87,7 +84,7 @@ public static function validation(array &$conditions): void
         $conditions = $finalConditions;
     }
 
-    protected static function getConditionKeyword(array $condition): ConditionKeyword | bool
+    protected static function getConditionKeyword(array $condition): ConditionKeyword
     {
         foreach (ConditionKeyword::cases() as $case) {
             if (
@@ -99,7 +96,7 @@ protected static function getConditionKeyword(array $condition): ConditionKeywor
             }
         }
 
-        return false;
+        throw new InvalidFieldException('no valid condition keyword found');
     }
 
     public static function getMandatoryElements(): array
diff --git a/src/Dictionary.php b/src/Dictionary.php
index 340f65f..87f8448 100644
--- a/src/Dictionary.php
+++ b/src/Dictionary.php
@@ -7,14 +7,14 @@ final class Dictionary
     private const FILE = 'en';
     private const DICTIONARY_DIRECTORY = '/storage/dictionary/';
 
-    private readonly string $filePath;
+    private readonly ?string $filePath;
 
     public function __construct(?string $filePath = null)
     {
         $this->filePath = $this->generateFilePath($filePath);
     }
 
-    private function generateFilePath(?string $filePath = null)
+    private function generateFilePath(?string $filePath = null): ?string
     {
         return is_file($filePath ?? '')
             ? $filePath
diff --git a/src/Parser/Extension/BlueprintInterpreter.php b/src/Parser/Extension/BlueprintInterpreter.php
index 275f659..0dbab2c 100644
--- a/src/Parser/Extension/BlueprintInterpreter.php
+++ b/src/Parser/Extension/BlueprintInterpreter.php
@@ -80,7 +80,7 @@ protected function matchHit(Component $component, array $row): bool
     {
         $found = false;
         /** @var Condition $condition */
-        foreach ($component->conditions as $condition) {
+        foreach ($component->conditions ?? [] as $condition) {
             $passedCondition = false;
             foreach ($condition->columns as $column) {
                 if (isset($row[$column - 1])) {
@@ -101,7 +101,7 @@ protected function matchHit(Component $component, array $row): bool
         return $found;
     }
 
-    protected function matchNext($index): bool
+    protected function matchNext(int $index): bool
     {
         return $this->lastHitIndex === $index - 1;
     }
diff --git a/src/Parser/Parser.php b/src/Parser/Parser.php
index d076a30..5e7f284 100644
--- a/src/Parser/Parser.php
+++ b/src/Parser/Parser.php
@@ -91,7 +91,9 @@ public function getParsedContentPlugin(): ParserPluginInterface
      */
     public function getAsObject(): stdClass
     {
-        return json_decode(json_encode($this->getAsArray()));
+        $json = json_encode($this->getAsArray());
+
+        return $json === false ? new stdClass() : json_decode($json);
     }
 
     /**
diff --git a/src/Parser/ParserBuilder.php b/src/Parser/ParserBuilder.php
index 95d6686..907da4f 100644
--- a/src/Parser/ParserBuilder.php
+++ b/src/Parser/ParserBuilder.php
@@ -43,7 +43,7 @@ public function addBlueprint(Blueprint $blueprint): self
 
     public function addFile(string $path): self
     {
-        $this->fileContent = $this->load($path, length: $this->maxFileLength);
+        $this->fileContent = $this->load($path);
 
         return $this;
     }
diff --git a/src/Parser/Utils/IOCapable.php b/src/Parser/Utils/IOCapable.php
index f4dd200..707123d 100644
--- a/src/Parser/Utils/IOCapable.php
+++ b/src/Parser/Utils/IOCapable.php
@@ -11,6 +11,7 @@ trait IOCapable
 
     private string $path = '';
 
+    /** @var resource */
     private $file;
 
     /**
@@ -20,13 +21,22 @@ trait IOCapable
      */
     protected function writeTemporaryFile(string $content): string
     {
-        $this->path = tempnam(sys_get_temp_dir(), __FUNCTION__);
-        $this->file = fopen($this->path, 'r+b');
+        $path = tempnam(sys_get_temp_dir(), __FUNCTION__);
 
-        if (!is_resource($this->file)) {
+        if (!$path) {
+            throw new UnableToCreateFileException('Unable to get a temporary file path');
+        }
+
+        $this->path = $path;
+
+        $file = fopen($this->path, 'r+b');
+
+        if (!is_resource($file)) {
             throw new UnableToCreateFileException("Unable to create temporary file in {$this->path}");
         }
 
+        $this->file = $file;
+
         if (!is_writable($this->path)) {
             throw new UnableToCreateFileException("Unable to modify temporary file in {$this->path}");
         }
@@ -41,10 +51,10 @@ protected function deleteTemporaryFile(): bool
         return $this->path ? unlink($this->path) : true;
     }
 
-    private function loadFromLink($url): string
+    private function loadFromLink(string $url): string
     {
         // TODO: use curl ... maybe
-        $content = \file_get_contents($url, length: $this->maxFileLength);
+        $content = \file_get_contents($url, length: $this->maxFileLength ?? null);
 
         if ($content === false) {
             throw new InvalidArgumentException("unable to load file from link: {$url}");
@@ -53,13 +63,19 @@ private function loadFromLink($url): string
         return $content;
     }
 
-    private function loadFromPath($path): string
+    private function loadFromPath(string $path): string
     {
         if (!is_readable($path)) {
-            throw new InvalidArgumentException("unable to read file from link: {$path}");
+            throw new InvalidArgumentException("unable to read file from path: {$path}");
         }
 
-        return \file_get_contents($path, length: $this->maxFileLength);
+        $content = \file_get_contents($path, length: $this->maxFileLength ?? null);
+
+        if ($content === false) {
+            throw new InvalidArgumentException("unable to load file from path: {$path}");
+        }
+
+        return $content;
     }
 
     /**
@@ -67,7 +83,7 @@ private function loadFromPath($path): string
      *
      * @return string the read data or false on failure
      */
-    protected function load(string $parameter, int $length): string
+    protected function load(string $parameter): string
     {
         if (filter_var($parameter, \FILTER_VALIDATE_URL)) {
             return $this->loadFromLink($parameter);
diff --git a/tests/Blueprint/BlueprintBuilderTest.php b/tests/Blueprint/BlueprintBuilderTest.php
index 16bf72b..1dcc55d 100644
--- a/tests/Blueprint/BlueprintBuilderTest.php
+++ b/tests/Blueprint/BlueprintBuilderTest.php
@@ -15,9 +15,9 @@ class BlueprintBuilderTest extends TestCase
     protected string $blueprintsDirectory = STORAGE_DIRECTORY . '/blueprints/';
 
 
-    public function testCreateFromString()
+    public function testCreateFromString(): void
     {
-        $rawFile = file_get_contents($this->blueprintsDirectory .  'valid.yaml');
+        $rawFile = (string) file_get_contents($this->blueprintsDirectory .  'valid.yaml');
 
         $builder = new BlueprintBuilder(new BlueprintHelper());
         $builder->parse($rawFile);
@@ -26,7 +26,7 @@ public function testCreateFromString()
         $this->assertInstanceOf(BlueprintInterface::class, $blueprint);
     }
 
-    public function testCreateFromPath()
+    public function testCreateFromPath(): void
     {
         $path = $this->blueprintsDirectory .  'valid.yaml';
 
@@ -40,7 +40,7 @@ public function testCreateFromPath()
     /**
      * @dataProvider emptyStreamsProvider
      */
-    public function testThrowingExceptionOnEmptyStream(string $stream, bool $isPath)
+    public function testThrowingExceptionOnEmptyStream(string $stream, bool $isPath): void
     {
         $this->expectException(InvalidBlueprintException::class);
         $builder = new BlueprintBuilder(new BlueprintHelper());
@@ -51,7 +51,7 @@ public function testThrowingExceptionOnEmptyStream(string $stream, bool $isPath)
         }
         $_ = $builder->build();
     }
-    public function emptyStreamsProvider()
+    public function emptyStreamsProvider(): array
     {
         return [
             ['', false],
diff --git a/tests/Blueprint/BlueprintTest.php b/tests/Blueprint/BlueprintTest.php
index 7a99f1b..d61cae5 100644
--- a/tests/Blueprint/BlueprintTest.php
+++ b/tests/Blueprint/BlueprintTest.php
@@ -15,9 +15,9 @@ class BlueprintTest extends TestCase
 {
     protected string $blueprintsDirectory = STORAGE_DIRECTORY . '/blueprints/';
 
-    public function testSuccessfullyCreateBlueprint()
+    public function testSuccessfullyCreateBlueprint(): void
     {
-        $rawFile = file_get_contents($this->blueprintsDirectory .  'valid.yaml');
+        $rawFile = (string) file_get_contents($this->blueprintsDirectory .  'valid.yaml');
         $blueprint = Blueprint::from(
             \yaml_parse($rawFile),
             $this->blueprintsDirectory .  'valid.yaml',
@@ -29,14 +29,15 @@ public function testSuccessfullyCreateBlueprint()
 
     /**
      * @dataProvider invalidFilesProvider
+     * @param class-string<\Throwable> $exception
      */
-    public function testThrowingExceptionOnInvalidBlueprint(string $fileName, string $exception)
+    public function testThrowingExceptionOnInvalidBlueprint(string $fileName, string $exception): void
     {
         $this->expectException($exception);
         $path = $this->blueprintsDirectory . $fileName . '.yaml';
         Blueprint::from(\yaml_parse_file($path), 'some-path', new BlueprintHelper());
     }
-    public function invalidFilesProvider()
+    public function invalidFilesProvider(): array
     {
         return [
             ['invalid_blueprint_1', InvalidBlueprintException::class],
diff --git a/tests/Blueprint/Components/ComponentsTest.php b/tests/Blueprint/Components/ComponentsTest.php
index bc701ab..3d78ba5 100644
--- a/tests/Blueprint/Components/ComponentsTest.php
+++ b/tests/Blueprint/Components/ComponentsTest.php
@@ -16,7 +16,7 @@ class ComponentsTest extends TestCase
 {
     protected string $blueprintsDirectory = STORAGE_DIRECTORY . '/blueprints/';
 
-    protected $helper;
+    protected mixed $helper;
 
     public function setUp(): void
     {
@@ -25,8 +25,9 @@ public function setUp(): void
 
     /**
      * @dataProvider invalidFilesProvider
+     * @param class-string<\Throwable> $exception
      */
-    public function testThrowingExceptionOnInvalidBlueprint(string $fileName, string $exception)
+    public function testThrowingExceptionOnInvalidBlueprint(string $fileName, string $exception): void
     {
         $this->expectException($exception);
         $path = $this->blueprintsDirectory . $fileName . '.yaml';
@@ -35,7 +36,7 @@ public function testThrowingExceptionOnInvalidBlueprint(string $fileName, string
         $_ = $builder->load($path)
             ->build();
     }
-    public function invalidFilesProvider()
+    public function invalidFilesProvider(): array
     {
         return [
             ['invalid_component_1', InvalidComponentException::class],
@@ -45,7 +46,7 @@ public function invalidFilesProvider()
     /**
      * @dataProvider validParametersDataProvider
      */
-    public function testCreateFromParameters($parametersArray)
+    public function testCreateFromParameters(array $parametersArray): void
     {
         $components = Components::from($parametersArray, new BlueprintHelper());
 
@@ -69,7 +70,7 @@ public function testCreateFromParameters($parametersArray)
             $components->components,
         );
     }
-    public function validParametersDataProvider()
+    public function validParametersDataProvider(): array
     {
         return [
             [
@@ -92,13 +93,14 @@ public function validParametersDataProvider()
 
     /**
      * @dataProvider invalidParametersDataProvider
+     * @param class-string<\Throwable> $exception
      */
-    public function testCreateFromInvalidParameters($parametersArray, $exception)
+    public function testCreateFromInvalidParameters(array $parametersArray, string $exception): void
     {
         $this->expectException($exception);
         $_ = Components::from($parametersArray, $this->helper);
     }
-    public function invalidParametersDataProvider()
+    public function invalidParametersDataProvider(): array
     {
         return [
             [
diff --git a/tests/Blueprint/Components/ConditionsTest.php b/tests/Blueprint/Components/ConditionsTest.php
index 0dfa4aa..9c4191b 100644
--- a/tests/Blueprint/Components/ConditionsTest.php
+++ b/tests/Blueprint/Components/ConditionsTest.php
@@ -16,14 +16,14 @@ class ConditionsTest extends TestCase
     /**
      * @dataProvider validParametersDataProvider
      */
-    public function testCreateFromParameters($parametersArray, $expected)
+    public function testCreateFromParameters(array $parametersArray, array $expected): void
     {
         $conditions = Conditions::from($parametersArray, new BlueprintHelper());
 
         $this->assertIsIterable($conditions);
         $this->assertEquals($conditions->conditions, $expected);
     }
-    public function validParametersDataProvider()
+    public function validParametersDataProvider(): array
     {
         return [
             [
@@ -51,13 +51,14 @@ public function validParametersDataProvider()
 
     /**
      * @dataProvider invalidParametersDataProvider
+     * @param class-string<\Throwable> $exception
      */
-    public function testCreateFromInvalidParameters($parametersArray, $exception)
+    public function testCreateFromInvalidParameters(array $parametersArray, string $exception): void
     {
         $this->expectException($exception);
         $_ = Conditions::from($parametersArray, new BlueprintHelper());
     }
-    public function invalidParametersDataProvider()
+    public function invalidParametersDataProvider(): array
     {
         return [
             [
diff --git a/tests/Blueprint/Components/FieldsTest.php b/tests/Blueprint/Components/FieldsTest.php
index 297617b..4e8cf95 100644
--- a/tests/Blueprint/Components/FieldsTest.php
+++ b/tests/Blueprint/Components/FieldsTest.php
@@ -18,14 +18,14 @@ class FieldsTest extends TestCase
     /**
      * @dataProvider validParametersDataProvider
      */
-    public function testCreateFromParameters($parametersArray, $expected)
+    public function testCreateFromParameters(array $parametersArray, array $expected): void
     {
         $fields = Fields::from($parametersArray, new BlueprintHelper());
 
         $this->assertIsIterable($fields);
         $this->assertEquals($fields->fields, $expected);
     }
-    public function validParametersDataProvider()
+    public function validParametersDataProvider(): array
     {
         return [
             [
@@ -51,13 +51,14 @@ public function validParametersDataProvider()
 
     /**
      * @dataProvider invalidParametersDataProvider
+     * @param class-string<\Throwable> $exception
      */
-    public function testCreateFromInvalidParameters($parametersArray, $exception)
+    public function testCreateFromInvalidParameters(array $parametersArray, string $exception): void
     {
         $this->expectException($exception);
         $_ = Fields::from($parametersArray, new BlueprintHelper());
     }
-    public function invalidParametersDataProvider()
+    public function invalidParametersDataProvider(): array
     {
         return [
             [
diff --git a/tests/DictionaryTest.php b/tests/DictionaryTest.php
index b4b59cb..7ce3f5c 100644
--- a/tests/DictionaryTest.php
+++ b/tests/DictionaryTest.php
@@ -11,7 +11,7 @@ class DictionaryTest extends TestCase
 {
     private string $storageTestDirectory = STORAGE_DIRECTORY . '/dictionaries/';
 
-    public function testCreateObject()
+    public function testCreateObject(): void
     {
         $this->assertInstanceOf(
             Dictionary::class,
@@ -22,7 +22,7 @@ public function testCreateObject()
     /**
      * @dataProvider getDataProvider
      */
-    public function testCanGetValue($key, $default, $file, $actual)
+    public function testCanGetValue(string $key, ?string $default, string $file, string $actual): void
     {
         $dictionary = new Dictionary($this->storageTestDirectory . $file);
 
@@ -31,7 +31,7 @@ public function testCanGetValue($key, $default, $file, $actual)
             $actual,
         );
     }
-    public function getDataProvider()
+    public function getDataProvider(): array
     {
         return [
             ['test.my.limits', null, 'valid.php', 'you %s'],
@@ -42,7 +42,7 @@ public function getDataProvider()
     /**
      * @dataProvider formattedValuesDataProvider
      */
-    public function testCanFormattedGetValue($key, $default, $file, $actual, $values)
+    public function testCanFormattedGetValue(string $key, ?string $default, string $file, string $actual, array $values): void
     {
         $dictionary = new Dictionary($this->storageTestDirectory . $file);
 
@@ -51,7 +51,7 @@ public function testCanFormattedGetValue($key, $default, $file, $actual, $values
             $actual,
         );
     }
-    public function formattedValuesDataProvider()
+    public function formattedValuesDataProvider(): array
     {
         return [
             ['test.my.limits', null, 'valid.php', 'you fool', ['fool']],
diff --git a/tests/HelperTest.php b/tests/HelperTest.php
index 3af1c40..9d65937 100644
--- a/tests/HelperTest.php
+++ b/tests/HelperTest.php
@@ -13,12 +13,11 @@ class HelperTest extends TestCase
     /**
      * @dataProvider arraysDataProvider
      */
-    public function testCanProcessArray(array $raw, array $actual, string $separator)
+    public function testCanProcessArray(array $raw, array $actual, string $separator): void
     {
-
         $this->assertEquals(Helper::toOneDimensionArray(array: $raw, separator: $separator), $actual);
     }
-    public function arraysDataProvider()
+    public function arraysDataProvider(): array
     {
         return [
             [
@@ -39,11 +38,11 @@ public function arraysDataProvider()
         ];
     }
 
-    public function testCanDetectDuplicateKeys()
+    public function testCanDetectDuplicateKeys(): void
     {
         $array = ['i' => ['hate.you' => false, 'hate' => ['you' => true]]];
 
         $this->expectException(Exception::class);
-        $a = Helper::toOneDimensionArray($array, separator: '.');
+        $_ = Helper::toOneDimensionArray($array, separator: '.');
     }
 }
diff --git a/tests/JustExampleTest.php b/tests/JustExampleTest.php
index 87ee2f6..52906ce 100644
--- a/tests/JustExampleTest.php
+++ b/tests/JustExampleTest.php
@@ -11,11 +11,11 @@ class JustExampleTest extends TestCase
     /**
      * @dataProvider exampleOneDataProvider
      */
-    public function testExampleOne($expected, $actual)
+    public function testExampleOne(int $expected, int $actual): void
     {
         $this->assertEquals($expected, $actual);
     }
-    public function exampleOneDataProvider()
+    public function exampleOneDataProvider(): array
     {
         return [
             [1, 1],
@@ -23,7 +23,7 @@ public function exampleOneDataProvider()
         ];
     }
 
-    public function testExampleTwo()
+    public function testExampleTwo(): void
     {
         $this->assertEquals(1, 1);
     }
diff --git a/tests/Parser/Extension/Spreadsheet/SpreadsheetTest.php b/tests/Parser/Extension/Spreadsheet/SpreadsheetTest.php
deleted file mode 100644
index 4ccefc1..0000000
--- a/tests/Parser/Extension/Spreadsheet/SpreadsheetTest.php
+++ /dev/null
@@ -1,15 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace HusamAwadhi\PowerParserTests\Parser\Extension\Spreadsheet;
-
-use PHPUnit\Framework\TestCase;
-
-class SpreadsheetTest extends TestCase
-{
-    public function testDummy()
-    {
-        $this->assertEquals(1, 1);
-    }
-}
diff --git a/tests/Parser/ParserBuilderTest.php b/tests/Parser/ParserBuilderTest.php
index 34576cc..49bfe5a 100644
--- a/tests/Parser/ParserBuilderTest.php
+++ b/tests/Parser/ParserBuilderTest.php
@@ -4,7 +4,6 @@
 
 namespace HusamAwadhi\PowerParserTests\Parser;
 
-use HusamAwadhi\PowerParser\Blueprint\Blueprint;
 use HusamAwadhi\PowerParser\Blueprint\BlueprintBuilder;
 use HusamAwadhi\PowerParser\Blueprint\BlueprintHelper;
 use HusamAwadhi\PowerParser\Exception\InvalidArgumentException;
@@ -20,7 +19,7 @@ class ParserBuilderTest extends TestCase
     protected string $blueprintsDirectory = STORAGE_DIRECTORY . '/blueprints/';
     protected string $excelFile = STORAGE_DIRECTORY . '/sample.xlsx';
 
-    public function testParserCreatedSuccessfully()
+    public function testParserCreatedSuccessfully(): void
     {
         $builder = new ParserBuilder();
         $blueprintBuilder = new BlueprintBuilder(new BlueprintHelper());
@@ -35,7 +34,7 @@ public function testParserCreatedSuccessfully()
         $this->assertInstanceOf(Parser::class, $parser);
     }
 
-    public function testExceptionWhenNoBlueprint()
+    public function testExceptionWhenNoBlueprint(): void
     {
         $this->expectException(MissingElementException::class);
 
@@ -46,7 +45,7 @@ public function testExceptionWhenNoBlueprint()
             ->build();
     }
 
-    public function testExceptionWhenNoFile()
+    public function testExceptionWhenNoFile(): void
     {
         $this->expectException(MissingElementException::class);
 
@@ -60,7 +59,7 @@ public function testExceptionWhenNoFile()
             ->build();
     }
 
-    public function testExceptionWhenFileNotFound()
+    public function testExceptionWhenFileNotFound(): void
     {
         $this->expectException(InvalidArgumentException::class);
 
@@ -71,7 +70,7 @@ public function testExceptionWhenFileNotFound()
             ->build();
     }
 
-    public function testExceptionWhenRegisteringDuplicateExtension()
+    public function testExceptionWhenRegisteringDuplicateExtension(): void
     {
         $this->expectException(InvalidPLuginException::class);
 
diff --git a/tests/Parser/ParserTest.php b/tests/Parser/ParserTest.php
index bd212c2..093a608 100644
--- a/tests/Parser/ParserTest.php
+++ b/tests/Parser/ParserTest.php
@@ -20,8 +20,8 @@ class ParserTest extends TestCase
     protected string $excelFile = STORAGE_DIRECTORY . '/sample.xlsx';
     protected string $csvFile = STORAGE_DIRECTORY . '/sample.csv';
     protected Blueprint $blueprint;
-    protected $dummyPlugin;
-    protected $dummyPlugin2;
+    protected mixed $dummyPlugin;
+    protected mixed $dummyPlugin2;
 
     public function setUp(): void
     {
@@ -38,23 +38,23 @@ public function setUp(): void
             ->willReturn(['exe']);
     }
 
-    public function testParserCreatedSuccessfully()
+    public function testParserCreatedSuccessfully(): void
     {
         $parser = new Parser(
             $this->blueprint,
-            \file_get_contents($this->excelFile),
+            (string) \file_get_contents($this->excelFile),
             [Spreadsheet::class => new Spreadsheet()]
         );
 
         $this->assertInstanceOf(Parser::class, $parser);
     }
 
-    public function testListOfSupportedExtensions()
+    public function testListOfSupportedExtensions(): void
     {
 
         $parser = new Parser(
             $this->blueprint,
-            \file_get_contents($this->excelFile),
+            (string) \file_get_contents($this->excelFile),
             [
                 Spreadsheet::class => new Spreadsheet(),
                 $this->dummyPlugin::class => $this->dummyPlugin
@@ -70,7 +70,7 @@ public function testListOfSupportedExtensions()
         );
     }
 
-    public function testSuccessfullyGetRecommendedPlugin()
+    public function testSuccessfullyGetRecommendedPlugin(): void
     {
         $builder = new BlueprintBuilder(new BlueprintHelper());
         $builder->load($this->blueprintsDirectory . 'valid_exe.yaml');
@@ -78,7 +78,7 @@ public function testSuccessfullyGetRecommendedPlugin()
 
         $parser = new Parser(
             $blueprint,
-            \file_get_contents($this->excelFile),
+            (string) \file_get_contents($this->excelFile),
             [
                 $this->dummyPlugin::class => $this->dummyPlugin,
                 $this->dummyPlugin2::class => $this->dummyPlugin2,
@@ -88,7 +88,7 @@ public function testSuccessfullyGetRecommendedPlugin()
         $this->assertEquals($this->dummyPlugin::class, $parser->getRecommendedPluginName());
     }
 
-    public function testSuccessfullyOverrideRecommendedPlugin()
+    public function testSuccessfullyOverrideRecommendedPlugin(): void
     {
         $builder = new BlueprintBuilder(new BlueprintHelper());
         $builder->load($this->blueprintsDirectory . 'valid_exe.yaml');
@@ -96,7 +96,7 @@ public function testSuccessfullyOverrideRecommendedPlugin()
 
         $parser = new Parser(
             $blueprint,
-            \file_get_contents($this->excelFile),
+            (string) \file_get_contents($this->excelFile),
             [
                 $this->dummyPlugin::class => $this->dummyPlugin,
                 $this->dummyPlugin2::class => $this->dummyPlugin2,
@@ -109,15 +109,17 @@ public function testSuccessfullyOverrideRecommendedPlugin()
         );
     }
 
-    public function testSuccessfullyIgnoreOverridingIfExtensionDoesNotSupport()
+    public function testSuccessfullyIgnoreOverridingIfExtensionDoesNotSupport(): void
     {
+        /** @var ParserPluginInterface[] */
+        $plugins =             [
+            Spreadsheet::class => new Spreadsheet(),
+            $this->dummyPlugin::class => $this->dummyPlugin
+        ];
         $parser = new Parser(
             $this->blueprint,
-            \file_get_contents($this->excelFile),
-            [
-                Spreadsheet::class => new Spreadsheet(),
-                $this->dummyPlugin::class => $this->dummyPlugin
-            ]
+            (string) \file_get_contents($this->excelFile),
+            $plugins
         );
 
         $this->assertEquals(
@@ -126,24 +128,24 @@ public function testSuccessfullyIgnoreOverridingIfExtensionDoesNotSupport()
         );
     }
 
-    public function testThrowsExceptionOnUnsupportedExtension()
+    public function testThrowsExceptionOnUnsupportedExtension(): void
     {
         $this->expectException(UnsupportedExtensionException::class);
 
         $parser = new Parser(
             $this->blueprint,
-            \file_get_contents($this->excelFile),
+            (string) \file_get_contents($this->excelFile),
             [$this->dummyPlugin::class => $this->dummyPlugin]
         );
 
         $_ = $parser->getRecommendedPluginName();
     }
 
-    public function testParseContent()
+    public function testParseContent(): void
     {
         $parser = new Parser(
             $this->blueprint,
-            \file_get_contents($this->excelFile),
+            (string) \file_get_contents($this->excelFile),
             [Spreadsheet::class => new Spreadsheet()]
         );
 
@@ -152,13 +154,13 @@ public function testParseContent()
         $this->assertInstanceOf(ParserPluginInterface::class, $parser->getParsedContentPlugin());
     }
 
-    public function testThrowsExceptionIfContentNotParsedYet()
+    public function testThrowsExceptionIfContentNotParsedYet(): void
     {
         $this->expectException(InvalidArgumentException::class);
 
         $parser = new Parser(
             $this->blueprint,
-            \file_get_contents($this->excelFile),
+            (string) \file_get_contents($this->excelFile),
             [Spreadsheet::class => new Spreadsheet()]
         );
 
@@ -168,7 +170,7 @@ public function testThrowsExceptionIfContentNotParsedYet()
     /**
      * @dataProvider parsedCSVContentDataProvider
      */
-    public function testGettingParsedCSVContentAsJson($expectedArray)
+    public function testGettingParsedCSVContentAsJson(array $expectedArray): void
     {
         $builder = new BlueprintBuilder(new BlueprintHelper());
         $builder->load($this->blueprintsDirectory . 'valid_csv.yaml');
@@ -176,15 +178,15 @@ public function testGettingParsedCSVContentAsJson($expectedArray)
 
         $parser = new Parser(
             $blueprint,
-            \file_get_contents($this->csvFile),
+            (string) \file_get_contents($this->csvFile),
             [Spreadsheet::class => new Spreadsheet()]
         );
 
         $parser->parse();
 
         $this->assertJsonStringEqualsJsonString(
-            json_encode($expectedArray),
-            json_encode($parser)
+            (string) json_encode($expectedArray),
+            (string) json_encode($parser)
         );
     }
     public function parsedCSVContentDataProvider(): array
@@ -297,18 +299,18 @@ public function parsedCSVContentDataProvider(): array
     /**
      * @dataProvider parsedExcelContentDataProvider
      */
-    public function testGettingParsedExcelContentAsObject($expectedArray)
+    public function testGettingParsedExcelContentAsObject(array $expectedArray): void
     {
         $parser = new Parser(
             $this->blueprint,
-            \file_get_contents($this->excelFile),
+            (string) \file_get_contents($this->excelFile),
             [Spreadsheet::class => new Spreadsheet()]
         );
 
         $parser->parse();
 
         $this->assertEquals(
-            json_decode(json_encode($expectedArray)),
+            json_decode((string) json_encode($expectedArray)),
             $parser->getAsObject()
         );
     }
@@ -316,11 +318,11 @@ public function testGettingParsedExcelContentAsObject($expectedArray)
     /**
      * @dataProvider parsedExcelContentDataProvider
      */
-    public function testGettingParsedExcelContentAsArray($expectedArray)
+    public function testGettingParsedExcelContentAsArray(array $expectedArray): void
     {
         $parser = new Parser(
             $this->blueprint,
-            \file_get_contents($this->excelFile),
+            (string) \file_get_contents($this->excelFile),
             [Spreadsheet::class => new Spreadsheet()]
         );
         $parser->parse();
@@ -331,19 +333,19 @@ public function testGettingParsedExcelContentAsArray($expectedArray)
     /**
      * @dataProvider parsedExcelContentDataProvider
      */
-    public function testGettingParsedExcelContentAsJson($expectedArray)
+    public function testGettingParsedExcelContentAsJson(array $expectedArray): void
     {
         $parser = new Parser(
             $this->blueprint,
-            \file_get_contents($this->excelFile),
+            (string) \file_get_contents($this->excelFile),
             [Spreadsheet::class => new Spreadsheet()]
         );
 
         $parser->parse();
 
         $this->assertJsonStringEqualsJsonString(
-            json_encode($expectedArray),
-            json_encode($parser)
+            (string) json_encode($expectedArray),
+            (string) json_encode($parser)
         );
     }
 
@@ -576,7 +578,7 @@ public function parsedExcelContentDataProvider(): array
         ];
     }
 
-    public function testThrowsExceptionOnMissingMandatoryComponent()
+    public function testThrowsExceptionOnMissingMandatoryComponent(): void
     {
         $this->expectException(InvalidArgumentException::class);
 
@@ -586,7 +588,7 @@ public function testThrowsExceptionOnMissingMandatoryComponent()
 
         $parser = new Parser(
             $blueprint,
-            \file_get_contents($this->csvFile),
+            (string) \file_get_contents($this->csvFile),
             [Spreadsheet::class => new Spreadsheet()]
         );
 
@@ -596,7 +598,7 @@ public function testThrowsExceptionOnMissingMandatoryComponent()
     /**
      * @dataProvider parsedExcelContentWithProcessorsDataProvider
      */
-    public function testGettingParsedExcelContentAsJsonWithProcessors($expectedArray)
+    public function testGettingParsedExcelContentAsJsonWithProcessors(array $expectedArray): void
     {
         $builder = new BlueprintBuilder(new BlueprintHelper());
         $builder->load($this->blueprintsDirectory . 'valid_with_processors.yaml');
@@ -604,15 +606,15 @@ public function testGettingParsedExcelContentAsJsonWithProcessors($expectedArray
 
         $parser = new Parser(
             $blueprint,
-            \file_get_contents($this->excelFile),
+            (string) \file_get_contents($this->excelFile),
             [Spreadsheet::class => new Spreadsheet()]
         );
 
         $parser->parse();
 
         $this->assertJsonStringEqualsJsonString(
-            json_encode($expectedArray),
-            json_encode($parser)
+            (string) json_encode($expectedArray),
+            (string) json_encode($parser)
         );
     }
 
diff --git a/tests/PowerParserTest.php b/tests/PowerParserTest.php
index 9c3e805..cfdfbcd 100644
--- a/tests/PowerParserTest.php
+++ b/tests/PowerParserTest.php
@@ -22,7 +22,7 @@ protected function setUp(): void
         $this->powerParser =  new PowerParser();
     }
 
-    public function testSuccessfullyCreateParserBuilder()
+    public function testSuccessfullyCreateParserBuilder(): void
     {
         $builder = $this->powerParser->getParserBuilder(
             $this->blueprintsDirectory . 'valid.yaml',
@@ -32,7 +32,7 @@ public function testSuccessfullyCreateParserBuilder()
         $this->assertInstanceOf(ParserBuilder::class, $builder);
     }
 
-    public function testSuccessfullyCreateBlueprint()
+    public function testSuccessfullyCreateBlueprint(): void
     {
         $blueprint = $this->powerParser->createBlueprint(
             $this->blueprintsDirectory . 'valid.yaml',