Add integration tests for @font-face at-rule parsing fix

Co-authored-by: neilime <314088+neilime@users.noreply.github.com>

Author: Copilot

tests/TestSuite/LinterTest.php

@@ -247,4 +247,35 @@ public function testLintNotValidCssFile()
             $errors
         );
     }
+
+    public function testLintFontFaceWithSpecificProperties()
+    {
+        // This test verifies the fix for the @font-face at-rule parsing issue
+        // where the trailing brace was incorrectly included in the at-rule name,
+        // causing valid @font-face properties to be flagged as invalid.
+        
+        // Arrange
+        $css = '@font-face{font-family:Poppins;font-display:swap;src:url(font.woff2);unicode-range:U+0900-097F}';
+        
+        // Act
+        $errors = iterator_to_array($this->linter->lintString($css), false);
+        
+        // Assert
+        $this->assertEmpty($errors, 'Valid @font-face properties should not produce lint errors');
+    }
+
+    public function testLintFontFaceWithInvalidProperty()
+    {
+        // This test ensures that invalid properties are still caught within @font-face blocks
+        
+        // Arrange
+        $css = '@font-face{font-family:Poppins;invalid-property:value}';
+        
+        // Act
+        $errors = iterator_to_array($this->linter->lintString($css), false);
+        
+        // Assert
+        $this->assertCount(1, $errors, 'Invalid @font-face property should produce exactly one lint error');
+        $this->assertStringContains('invalid-property', $errors[0]->getMessage());
+    }
 }