M3-AP-008: Testabdeckung vervollständigt

pdf-umbenenner-adapter-out/src/test/java/de/gecheckt/pdf/umbenenner/adapter/outbound/pdfextraction/PdfTextExtractionPortAdapterTest.java

@@ -15,6 +15,7 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertInstanceOf;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
@@ -125,6 +126,28 @@ class PdfTextExtractionPortAdapterTest {
         assertNotNull(success.extractedText());  // May be empty, but not null
     }
 
+    @Test
+    void testCorruptedPdfReturnsTechnicalError() throws Exception {
+        // Create a file with binary garbage content – exists on disk but is not a valid PDF
+        Path corruptFile = tempDir.resolve("corrupt.pdf");
+        Files.write(corruptFile, "THIS IS NOT A PDF - RANDOM GARBAGE XYZ123!@#".getBytes());
+
+        SourceDocumentCandidate candidate = new SourceDocumentCandidate(
+            "corrupt.pdf",
+            Files.size(corruptFile),
+            new SourceDocumentLocator(corruptFile.toAbsolutePath().toString())
+        );
+
+        PdfExtractionResult result = adapter.extractTextAndPageCount(candidate);
+
+        // PDFBox cannot load a garbage file; the adapter must catch this and return TechnicalError
+        assertInstanceOf(PdfExtractionTechnicalError.class, result,
+            "Binary garbage file (not a real PDF) must yield TechnicalError, not Success");
+        PdfExtractionTechnicalError error = (PdfExtractionTechnicalError) result;
+        assertNotNull(error.errorMessage(), "TechnicalError must carry a non-null error message");
+        assertFalse(error.errorMessage().isBlank(), "TechnicalError message must not be blank");
+    }
+
     // --- Helper methods to create test PDFs ---
 
     /**