diff --git a/.github/workflows/continuous_integration.yml b/.github/workflows/continuous_integration.yml
index 375e7b9daa..cd0653d998 100644
--- a/.github/workflows/continuous_integration.yml
+++ b/.github/workflows/continuous_integration.yml
@@ -44,7 +44,7 @@ jobs:
           echo "::set-output name=dir::$(composer config cache-files-dir)"
 
       - name: composer-cache
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           path: ${{ steps.composercache.outputs.dir }}
           key: composer-${{ hashFiles('**/composer.json') }}-${{ matrix.install-args }}
@@ -61,7 +61,7 @@ jobs:
         run: "vendor/bin/phpunit"
 
       - name: phpstan-cache
-        uses: actions/cache@v4
+        uses: actions/cache@v5
         with:
           key: phpstan-${{ matrix.php-version }}-${{ matrix.install-args }}-${{ github.ref }}-${{ github.sha }}
           path: .phpstan-cache
@@ -79,13 +79,13 @@ jobs:
         run: composer cs-check
 
       - name: "Archive code coverage results"
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v6
         with:
           name: codeCoverage-${{ matrix.php-version }}-${{ github.run_id }}
           path: "build"
           overwrite: true
 
-      - uses: codecov/codecov-action@v5.5.0 # upload the coverage to codecov
+      - uses: codecov/codecov-action@v5.5.1 # upload the coverage to codecov
         with:
           fail_ci_if_error: false # optional (default = false) - Need CODECOV_TOKEN
         # Do not upload in forks, and only on php8.4, latest deps
diff --git a/.github/workflows/doc_generation.yml b/.github/workflows/doc_generation.yml
index 97caa41546..f96e79e728 100644
--- a/.github/workflows/doc_generation.yml
+++ b/.github/workflows/doc_generation.yml
@@ -22,7 +22,7 @@ jobs:
         uses: "actions/checkout@v5"
 
       - name: "Setup NodeJS"
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v5
         with:
           node-version: '20.x'
 
@@ -36,7 +36,7 @@ jobs:
 
       - name: "Deploy website"
         if: "${{ github.event_name == 'push' || github.event_name == 'release' }}"
-        uses: JamesIves/github-pages-deploy-action@v4.7.3
+        uses: JamesIves/github-pages-deploy-action@v4.7.6
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           branch: gh-pages # The branch the action should deploy to.
diff --git a/composer.json b/composer.json
index 520f02bbc5..00ccdb862c 100644
--- a/composer.json
+++ b/composer.json
@@ -21,8 +21,8 @@
         "psr/http-server-handler": "^1",
         "psr/http-server-middleware": "^1",
         "psr/simple-cache": "^1.0.1 || ^2 || ^3",
-        "symfony/cache": "^4.3 || ^5 || ^6 || ^7",
-        "symfony/expression-language": "^4 || ^5 || ^6 || ^7",
+        "symfony/cache": "^4.3 || ^5 || ^6 || ^7 || ^8",
+        "symfony/expression-language": "^4 || ^5 || ^6 || ^7 || ^8",
         "webonyx/graphql-php": "^v15.0",
         "kcs/class-finder": "^0.6.0"
     },
@@ -35,7 +35,7 @@
         "php-coveralls/php-coveralls": "^2.7",
         "phpstan/extension-installer": "^1.4",
         "phpstan/phpstan": "^2.0",
-        "phpunit/phpunit": "^10.5 || ^11.0",
+        "phpunit/phpunit": "^10.5 || ^11.0 || ^12.0",
         "symfony/var-dumper": "^6.4"
     },
     "suggest": {
diff --git a/src/Cache/FilesSnapshot.php b/src/Cache/FilesSnapshot.php
index 7ac70861ac..afed10f0c3 100644
--- a/src/Cache/FilesSnapshot.php
+++ b/src/Cache/FilesSnapshot.php
@@ -7,6 +7,7 @@
 use ReflectionClass;
 
 use function array_unique;
+use function is_file;
 use function Safe\filemtime;
 
 class FilesSnapshot
@@ -24,6 +25,10 @@ public static function for(array $files): self
         $dependencies = [];
 
         foreach (array_unique($files) as $file) {
+            if (! is_file($file)) {
+                continue;
+            }
+
             $dependencies[$file] = filemtime($file);
         }
 
diff --git a/src/ResolveUtils.php b/src/ResolveUtils.php
index b3aa657668..2f95d35f32 100644
--- a/src/ResolveUtils.php
+++ b/src/ResolveUtils.php
@@ -24,7 +24,7 @@ final class ResolveUtils
     public static function assertInnerReturnType(mixed $result, Type $type): void
     {
         if ($type instanceof NonNull && $result === null) {
-            throw TypeMismatchRuntimeException::unexpectedNullValue();
+            throw TypeMismatchRuntimeException::unexpectedNullValue($type);
         }
         if ($result === null) {
             return;
@@ -56,7 +56,7 @@ public static function assertInnerReturnType(mixed $result, Type $type): void
     public static function assertInnerInputType(mixed $input, Type $type): void
     {
         if ($type instanceof NonNull && $input === null) {
-            throw TypeMismatchRuntimeException::unexpectedNullValue();
+            throw TypeMismatchRuntimeException::unexpectedNullValue($type);
         }
         if ($input === null) {
             return;
diff --git a/src/TypeMismatchRuntimeException.php b/src/TypeMismatchRuntimeException.php
index c73e323dac..d121bb4809 100644
--- a/src/TypeMismatchRuntimeException.php
+++ b/src/TypeMismatchRuntimeException.php
@@ -4,6 +4,8 @@
 
 namespace TheCodingMachine\GraphQLite;
 
+use GraphQL\Type\Definition\Type;
+
 use function gettype;
 
 /**
@@ -11,9 +13,15 @@
  */
 class TypeMismatchRuntimeException extends GraphQLRuntimeException
 {
-    public static function unexpectedNullValue(): self
+    public static function unexpectedNullValue(Type|null $expectedType = null): self
     {
-        return new self('Unexpected null value for non nullable field.');
+        $expectedMessageTail = '';
+        if ($expectedType !== null) {
+            $expectedMessageTail = ' Expected: "' . $expectedType->toString() . '"';
+            // ToDo: support for NULL $expectedType should be dropped in the next major
+        }
+
+        return new self('Unexpected null value for non nullable field.' . $expectedMessageTail);
     }
 
     public static function expectedIterable(mixed $result): self
diff --git a/src/Utils/PropertyAccessor.php b/src/Utils/PropertyAccessor.php
index 1347d1151c..2d0b4bd76d 100644
--- a/src/Utils/PropertyAccessor.php
+++ b/src/Utils/PropertyAccessor.php
@@ -94,6 +94,7 @@ public static function setValue(object $instance, string $propertyName, mixed $v
         throw AccessPropertyException::createForUnwritableProperty($class, $propertyName);
     }
 
+    /** @param class-string $class */
     private static function isPublicProperty(string $class, string $propertyName): bool
     {
         if (! property_exists($class, $propertyName)) {
diff --git a/tests/Cache/FilesSnapshotTest.php b/tests/Cache/FilesSnapshotTest.php
index f45aa2c75e..a82baeb95a 100644
--- a/tests/Cache/FilesSnapshotTest.php
+++ b/tests/Cache/FilesSnapshotTest.php
@@ -69,9 +69,37 @@ public function testTracksChangesInFile(): void
         self::assertTrue($snapshot->changed());
     }
 
+    public function testIgnoresNonExistentFiles(): void
+    {
+        $nonExistentFile = '/path/to/non/existent/file.php';
+
+        $snapshot = FilesSnapshot::for([$nonExistentFile]);
+
+        self::assertFalse($snapshot->changed());
+    }
+
+    public function testIgnoresNonExistentFilesInMixedList(): void
+    {
+        $existingFile = (new \ReflectionClass(FooType::class))->getFileName();
+        $nonExistentFile1 = '/path/to/non/existent/file1.php';
+        $nonExistentFile2 = '/path/to/non/existent/file2.php';
+
+        $snapshot = FilesSnapshot::for([
+            $nonExistentFile1,
+            $existingFile,
+            $nonExistentFile2,
+        ]);
+
+        self::assertFalse($snapshot->changed());
+        
+        $this->touch($existingFile);
+
+        self::assertTrue($snapshot->changed());
+    }
+
     private function touch(string $fileName): void
     {
         touch($fileName, filemtime($fileName) + 1);
         clearstatcache();
     }
-}
\ No newline at end of file
+}
diff --git a/tests/Loggers/ExceptionLogger.php b/tests/Loggers/ExceptionLogger.php
index 612d0226ce..3a0a65861a 100644
--- a/tests/Loggers/ExceptionLogger.php
+++ b/tests/Loggers/ExceptionLogger.php
@@ -1,12 +1,15 @@
 <?php
 
+declare(strict_types=1);
 
 namespace TheCodingMachine\GraphQLite\Loggers;
 
-
+use Exception;
 use Psr\Log\AbstractLogger;
 use Psr\Log\LogLevel;
+use Stringable;
 use Throwable;
+
 use function in_array;
 
 /**
@@ -15,16 +18,14 @@
  */
 class ExceptionLogger extends AbstractLogger
 {
-    /**
-     * @inheritDoc
-     */
-    public function log($level, $message, array $context = array())
+    /** @inheritDoc */
+    public function log($level, $message, array $context = []): void
     {
         if (in_array($level, [LogLevel::EMERGENCY, LogLevel::ALERT, LogLevel::CRITICAL, LogLevel::ERROR, LogLevel::WARNING])) {
             if (isset($context['exception']) && $context['exception'] instanceof Throwable) {
                 throw $context['exception'];
             }
-            throw new \Exception($message);
+            throw new Exception($message);
         }
     }
 }
diff --git a/tests/ResolveUtilsTest.php b/tests/ResolveUtilsTest.php
index ca5a1e634c..041f42d4e7 100644
--- a/tests/ResolveUtilsTest.php
+++ b/tests/ResolveUtilsTest.php
@@ -12,6 +12,7 @@ class ResolveUtilsTest extends TestCase
     public function testAssertNull(): void
     {
         $this->expectException(TypeMismatchRuntimeException::class);
+        $this->expectExceptionMessage('Unexpected null value for non nullable field. Expected: "String!"');
         ResolveUtils::assertInnerReturnType(null, Type::nonNull(Type::string()));
     }
 
@@ -30,6 +31,7 @@ public function testAssertObjectOk(): void
     public function testAssertInputNull(): void
     {
         $this->expectException(TypeMismatchRuntimeException::class);
+        $this->expectExceptionMessage('Unexpected null value for non nullable field. Expected: "String!"');
         ResolveUtils::assertInnerInputType(null, Type::nonNull(Type::string()));
     }