diff --git a/requirement-checker/src/Checker.php b/requirement-checker/src/Checker.php
index e70c49adf..038fcea27 100644
--- a/requirement-checker/src/Checker.php
+++ b/requirement-checker/src/Checker.php
@@ -14,6 +14,7 @@
 
 namespace KevinGH\RequirementChecker;
 
+use InvalidArgumentException;
 use function count;
 
 /**
@@ -137,9 +138,10 @@ private static function retrieveRequirements(): RequirementCollection
 
         foreach ($config as $constraint) {
             $requirements->addRequirement(
-                'php' === $constraint['type']
-                    ? new IsPhpVersionFulfilled($constraint['condition'])
-                    : new IsExtensionFulfilled($constraint['condition']),
+                self::createCondition(
+                    $constraint['type'],
+                    $constraint['condition']
+                ),
                 $constraint['message'],
                 $constraint['helpMessage']
             );
@@ -147,4 +149,27 @@ private static function retrieveRequirements(): RequirementCollection
 
         return $requirements;
     }
+
+    /**
+     * @param string $type
+     * @param string $condition
+     */
+    private static function createCondition($type, $condition): IsFulfilled
+    {
+        switch ($type) {
+            case 'php':
+                return new IsPhpVersionFulfilled($condition);
+
+            case 'extension':
+                return new IsExtensionFulfilled($condition);
+
+            default:
+                throw new InvalidArgumentException(
+                    sprintf(
+                        'Unknown requirement type "%s".',
+                        $type,
+                    ),
+                );
+        }
+    }
 }
diff --git a/res/requirement-checker/src/Checker.php b/res/requirement-checker/src/Checker.php
index c6a70f52c..a8c2914c3 100644
--- a/res/requirement-checker/src/Checker.php
+++ b/res/requirement-checker/src/Checker.php
@@ -3,6 +3,7 @@
 declare (strict_types=1);
 namespace HumbugBox420\KevinGH\RequirementChecker;
 
+use InvalidArgumentException;
 use function count;
 final class Checker
 {
@@ -80,8 +81,19 @@ private static function retrieveRequirements() : RequirementCollection
         $config = (require self::$requirementsConfig);
         $requirements = new RequirementCollection();
         foreach ($config as $constraint) {
-            $requirements->addRequirement('php' === $constraint['type'] ? new IsPhpVersionFulfilled($constraint['condition']) : new IsExtensionFulfilled($constraint['condition']), $constraint['message'], $constraint['helpMessage']);
+            $requirements->addRequirement(self::createCondition($constraint['type'], $constraint['condition']), $constraint['message'], $constraint['helpMessage']);
         }
         return $requirements;
     }
+    private static function createCondition($type, $condition) : IsFulfilled
+    {
+        switch ($type) {
+            case 'php':
+                return new IsPhpVersionFulfilled($condition);
+            case 'extension':
+                return new IsExtensionFulfilled($condition);
+            default:
+                throw new InvalidArgumentException(\sprintf('Unknown requirement type "%s".', $type));
+        }
+    }
 }
diff --git a/src/RequirementChecker/AppRequirementsFactory.php b/src/RequirementChecker/AppRequirementsFactory.php
index 88e1a3934..743674cc5 100644
--- a/src/RequirementChecker/AppRequirementsFactory.php
+++ b/src/RequirementChecker/AppRequirementsFactory.php
@@ -30,7 +30,7 @@ final class AppRequirementsFactory
     private const SELF_PACKAGE = '__APPLICATION__';
 
     /**
-     * @return list<Requirement> Serialized configured requirements
+     * @return list<Requirement> Configured requirements
      */
     public static function create(
         DecodedComposerJson $composerJson,
@@ -103,7 +103,7 @@ private static function configureExtensionRequirements(
 
         foreach ($extensionRequirements as $extension => $packages) {
             foreach ($packages as $package) {
-                $requirements[] = Requirement::forExtension(
+                $requirements[] = Requirement::forRequiredExtension(
                     $extension,
                     self::SELF_PACKAGE === $package ? null : $package,
                 );
@@ -117,7 +117,7 @@ private static function configureExtensionRequirements(
      * Collects the extension required. It also accounts for the polyfills, i.e. if the polyfill
      * `symfony/polyfill-mbstring` is provided then the extension `ext-mbstring` will not be required.
      *
-     * @return array{array<string, true>, array<string, string>} Associative array containing the list of extensions required
+     * @return array<string, list<string>> Associative array containing the list of extensions required
      */
     private static function collectExtensionRequirements(
         DecodedComposerJson $composerJson,
@@ -148,7 +148,7 @@ private static function collectExtensionRequirements(
     /**
      * @param array<string, list<string>> $requirements The key is the extension name and the value the list of sources (app literal string or the package name).
      *
-     * @return array{array<string, true>, array<string, string>}
+     * @return array{array<string, true>, array<string, list<string>>}
      */
     private static function collectComposerJsonExtensionRequirements(
         DecodedComposerJson $composerJson,
@@ -176,7 +176,7 @@ private static function collectComposerJsonExtensionRequirements(
     /**
      * @param array<string, list<string>> $requirements The key is the extension name and the value the list of sources (app literal string or the package name).
      *
-     * @return array{array<string, true>, array<string, string>}
+     * @return array{array<string, true>, array<string, list<string>>}
      */
     private static function collectComposerLockExtensionRequirements(
         DecodedComposerLock $composerLock,
diff --git a/src/RequirementChecker/Requirement.php b/src/RequirementChecker/Requirement.php
index 601c9ac4a..e57c1c33b 100644
--- a/src/RequirementChecker/Requirement.php
+++ b/src/RequirementChecker/Requirement.php
@@ -55,7 +55,7 @@ public static function forPHP(string $requiredPhpVersion, ?string $packageName):
         );
     }
 
-    public static function forExtension(string $extension, ?string $packageName): self
+    public static function forRequiredExtension(string $extension, ?string $packageName): self
     {
         // TODO: review the message & help message
         return new self(
diff --git a/tests/RequirementChecker/AppRequirementsFactoryTest.php b/tests/RequirementChecker/AppRequirementsFactoryTest.php
index 555aaac71..b2c32e025 100644
--- a/tests/RequirementChecker/AppRequirementsFactoryTest.php
+++ b/tests/RequirementChecker/AppRequirementsFactoryTest.php
@@ -72,7 +72,7 @@ public static function lockContentsProvider(): iterable
             null,
             CompressionAlgorithm::GZ,
             [
-                Requirement::forExtension('zlib', null),
+                Requirement::forRequiredExtension('zlib', null),
             ],
         ];
 
@@ -81,7 +81,7 @@ public static function lockContentsProvider(): iterable
             null,
             CompressionAlgorithm::BZ2,
             [
-                Requirement::forExtension('bz2', null),
+                Requirement::forRequiredExtension('bz2', null),
             ],
         ];
 
@@ -90,7 +90,7 @@ public static function lockContentsProvider(): iterable
             '{}',
             CompressionAlgorithm::GZ,
             [
-                Requirement::forExtension('zlib', null),
+                Requirement::forRequiredExtension('zlib', null),
             ],
         ];
 
@@ -99,7 +99,7 @@ public static function lockContentsProvider(): iterable
             '{}',
             CompressionAlgorithm::BZ2,
             [
-                Requirement::forExtension('bz2', null),
+                Requirement::forRequiredExtension('bz2', null),
             ],
         ];
 
@@ -108,7 +108,7 @@ public static function lockContentsProvider(): iterable
             '{}',
             CompressionAlgorithm::GZ,
             [
-                Requirement::forExtension('zlib', null),
+                Requirement::forRequiredExtension('zlib', null),
             ],
         ];
 
@@ -117,7 +117,7 @@ public static function lockContentsProvider(): iterable
             '{}',
             CompressionAlgorithm::BZ2,
             [
-                Requirement::forExtension('bz2', null),
+                Requirement::forRequiredExtension('bz2', null),
             ],
         ];
 
@@ -136,7 +136,7 @@ public static function lockContentsProvider(): iterable
             CompressionAlgorithm::NONE,
             [
                 Requirement::forPHP('^7.1', null),
-                Requirement::forExtension('phar', null),
+                Requirement::forRequiredExtension('phar', null),
             ],
         ];
 
@@ -154,7 +154,7 @@ public static function lockContentsProvider(): iterable
             CompressionAlgorithm::NONE,
             [
                 Requirement::forPHP('^7.1', null),
-                Requirement::forExtension('phar', null),
+                Requirement::forRequiredExtension('phar', null),
             ],
         ];
 
@@ -181,7 +181,7 @@ public static function lockContentsProvider(): iterable
             CompressionAlgorithm::NONE,
             [
                 Requirement::forPHP('^7.1', null),
-                Requirement::forExtension('phar', null),
+                Requirement::forRequiredExtension('phar', null),
             ],
         ];
 
@@ -199,8 +199,8 @@ public static function lockContentsProvider(): iterable
             CompressionAlgorithm::GZ,
             [
                 Requirement::forPHP('^7.1', null),
-                Requirement::forExtension('zlib', null),
-                Requirement::forExtension('phar', null),
+                Requirement::forRequiredExtension('zlib', null),
+                Requirement::forRequiredExtension('phar', null),
             ],
         ];
 
@@ -218,8 +218,8 @@ public static function lockContentsProvider(): iterable
             CompressionAlgorithm::GZ,
             [
                 Requirement::forPHP('^7.1', null),
-                Requirement::forExtension('zlib', null),
-                Requirement::forExtension('phar', null),
+                Requirement::forRequiredExtension('zlib', null),
+                Requirement::forRequiredExtension('phar', null),
             ],
         ];
 
@@ -245,8 +245,8 @@ public static function lockContentsProvider(): iterable
             CompressionAlgorithm::GZ,
             [
                 Requirement::forPHP('^7.1', null),
-                Requirement::forExtension('zlib', null),
-                Requirement::forExtension('phar', null),
+                Requirement::forRequiredExtension('zlib', null),
+                Requirement::forRequiredExtension('phar', null),
             ],
         ];
 
@@ -316,7 +316,7 @@ public static function lockContentsProvider(): iterable
             null,
             CompressionAlgorithm::GZ,
             [
-                Requirement::forExtension('zlib', null),
+                Requirement::forRequiredExtension('zlib', null),
             ],
         ];
 
@@ -333,7 +333,7 @@ public static function lockContentsProvider(): iterable
                 JSON,
             CompressionAlgorithm::GZ,
             [
-                Requirement::forExtension('zlib', null),
+                Requirement::forRequiredExtension('zlib', null),
             ],
         ];
 
@@ -358,7 +358,7 @@ public static function lockContentsProvider(): iterable
                 JSON,
             CompressionAlgorithm::GZ,
             [
-                Requirement::forExtension('zlib', null),
+                Requirement::forRequiredExtension('zlib', null),
             ],
         ];
 
@@ -379,10 +379,10 @@ public static function lockContentsProvider(): iterable
             CompressionAlgorithm::NONE,
             [
                 Requirement::forPHP('>=5.3', null),
-                Requirement::forExtension('mbstring', null),
-                Requirement::forExtension('openssl', null),
-                Requirement::forExtension('pcre', null),
-                Requirement::forExtension('pdo_sqlite3', null),
+                Requirement::forRequiredExtension('mbstring', null),
+                Requirement::forRequiredExtension('openssl', null),
+                Requirement::forRequiredExtension('pcre', null),
+                Requirement::forRequiredExtension('pdo_sqlite3', null),
             ],
         ];
 
@@ -428,10 +428,10 @@ public static function lockContentsProvider(): iterable
             [
                 Requirement::forPHP('>=5.3', 'beberlei/assert'),
                 Requirement::forPHP('^5.3.2 || ^7.0', 'composer/ca-bundle'),
-                Requirement::forExtension('mbstring', 'beberlei/assert'),
-                Requirement::forExtension('openssl', 'composer/ca-bundle'),
-                Requirement::forExtension('openssl', 'acme/foo'),
-                Requirement::forExtension('pcre', 'composer/ca-bundle'),
+                Requirement::forRequiredExtension('mbstring', 'beberlei/assert'),
+                Requirement::forRequiredExtension('openssl', 'composer/ca-bundle'),
+                Requirement::forRequiredExtension('openssl', 'acme/foo'),
+                Requirement::forRequiredExtension('pcre', 'composer/ca-bundle'),
             ],
         ];
 
@@ -608,10 +608,10 @@ public static function lockContentsProvider(): iterable
             CompressionAlgorithm::NONE,
             [
                 Requirement::forPHP('>=5.3', null),
-                Requirement::forExtension('mbstring', 'beberlei/assert'),
-                Requirement::forExtension('openssl', 'composer/ca-bundle'),
-                Requirement::forExtension('openssl', 'acme/foo'),
-                Requirement::forExtension('pcre', 'composer/ca-bundle'),
+                Requirement::forRequiredExtension('mbstring', 'beberlei/assert'),
+                Requirement::forRequiredExtension('openssl', 'composer/ca-bundle'),
+                Requirement::forRequiredExtension('openssl', 'acme/foo'),
+                Requirement::forRequiredExtension('pcre', 'composer/ca-bundle'),
             ],
         ];
 
@@ -746,12 +746,12 @@ public static function lockContentsProvider(): iterable
             CompressionAlgorithm::NONE,
             [
                 Requirement::forPHP('^7.3', null),
-                Requirement::forExtension('mbstring', null),
-                Requirement::forExtension('mbstring', 'beberlei/assert'),
-                Requirement::forExtension('mbstring', 'composer/ca-bundle'),
-                Requirement::forExtension('json', null),
-                Requirement::forExtension('json', 'beberlei/assert'),
-                Requirement::forExtension('json', 'composer/ca-bundle'),
+                Requirement::forRequiredExtension('mbstring', null),
+                Requirement::forRequiredExtension('mbstring', 'beberlei/assert'),
+                Requirement::forRequiredExtension('mbstring', 'composer/ca-bundle'),
+                Requirement::forRequiredExtension('json', null),
+                Requirement::forRequiredExtension('json', 'beberlei/assert'),
+                Requirement::forRequiredExtension('json', 'composer/ca-bundle'),
             ],
         ];
 
@@ -773,7 +773,7 @@ public static function lockContentsProvider(): iterable
             CompressionAlgorithm::NONE,
             [
                 Requirement::forPHP('^7.3', null),
-                Requirement::forExtension('json', null),
+                Requirement::forRequiredExtension('json', null),
             ],
         ];
 
@@ -833,9 +833,9 @@ public static function lockContentsProvider(): iterable
             CompressionAlgorithm::NONE,
             [
                 Requirement::forPHP('^7.3', null),
-                Requirement::forExtension('json', null),
-                Requirement::forExtension('json', 'beberlei/assert'),
-                Requirement::forExtension('json', 'composer/ca-bundle'),
+                Requirement::forRequiredExtension('json', null),
+                Requirement::forRequiredExtension('json', 'beberlei/assert'),
+                Requirement::forRequiredExtension('json', 'composer/ca-bundle'),
             ],
         ];
 
diff --git a/tests/RequirementChecker/DecodedComposerJsonTest.php b/tests/RequirementChecker/DecodedComposerJsonTest.php
index d85dc2f5d..ac8dee87d 100644
--- a/tests/RequirementChecker/DecodedComposerJsonTest.php
+++ b/tests/RequirementChecker/DecodedComposerJsonTest.php
@@ -105,7 +105,7 @@ public static function composerJsonProvider(): iterable
             ],
         ];
 
-        yield 'packages and extensions required' => [
+        yield 'nominal' => [
             <<<'JSON'
                 {
                     "require": {
diff --git a/tests/RequirementChecker/RequirementTest.php b/tests/RequirementChecker/RequirementTest.php
index bbf2f9f84..011327dde 100644
--- a/tests/RequirementChecker/RequirementTest.php
+++ b/tests/RequirementChecker/RequirementTest.php
@@ -53,7 +53,7 @@ public function test_it_can_be_created_for_a_php_version_for_a_package(): void
 
     public function test_it_can_be_created_for_an_extension_constraint(): void
     {
-        $requirement = Requirement::forExtension('mbstring', null);
+        $requirement = Requirement::forRequiredExtension('mbstring', null);
 
         $expected = [
             'type' => 'extension',
@@ -67,7 +67,7 @@ public function test_it_can_be_created_for_an_extension_constraint(): void
 
     public function test_it_can_be_created_for_an_extension_constraint_for_a_package(): void
     {
-        $requirement = Requirement::forExtension('mbstring', 'box/test');
+        $requirement = Requirement::forRequiredExtension('mbstring', 'box/test');
 
         $expected = [
             'type' => 'extension',