Add: Validation for rotation angle and create unit tests for RotationController (#3162)

# Description of Changes

Please provide a summary of the changes, including:

- What was changed
- Why the change was made
- Any challenges encountered

Closes #(issue_number)

---

## Checklist

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code
- [x] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [x] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#6-testing)
for more details.

.github/labeler-config.yml

@@ -72,7 +72,8 @@ Devtools:
 Test:
   - changed-files:
     - any-glob-to-any-file: 'cucumber/**/*'
-    - any-glob-to-any-file: 'src/test**/*'
+    - any-glob-to-any-file: 'src/test/**/*'
+    - any-glob-to-any-file: 'src/testing/**/*'
     - any-glob-to-any-file: '.pre-commit-config'
     - any-glob-to-any-file: '.github/workflows/pre_commit.yml'
     - any-glob-to-any-file: '.github/workflows/scorecards.yml'

src/main/java/stirling/software/SPDF/controller/api/RotationController.java

@@ -43,6 +43,12 @@ public class RotationController {
             throws IOException {
         MultipartFile pdfFile = request.getFileInput();
         Integer angle = request.getAngle();
+
+        // Validate the angle is a multiple of 90
+        if (angle % 90 != 0) {
+            throw new IllegalArgumentException("Angle must be a multiple of 90");
+        }
+
         // Load the PDF document
         PDDocument document = pdfDocumentFactory.load(request);
 

src/test/java/stirling/software/SPDF/controller/api/RotationControllerTest.java

@@ -0,0 +1,74 @@
+package stirling.software.SPDF.controller.api;
+
+import org.apache.pdfbox.pdmodel.PDDocument;
+import org.apache.pdfbox.pdmodel.PDPage;
+import java.io.IOException;
+import org.apache.pdfbox.pdmodel.PDPageTree;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.http.ResponseEntity;
+import org.springframework.mock.web.MockMultipartFile;
+import stirling.software.SPDF.service.CustomPDFDocumentFactory;
+import stirling.software.SPDF.model.api.general.RotatePDFRequest;
+
+@ExtendWith(MockitoExtension.class)
+public class RotationControllerTest {
+
+    @Mock private CustomPDFDocumentFactory pdfDocumentFactory;
+
+    @InjectMocks private RotationController rotationController;
+
+    @Test
+    public void testRotatePDF() throws IOException {
+        // Create a mock file
+        MockMultipartFile mockFile =
+                new MockMultipartFile("file", "test.pdf", "application/pdf", new byte[] {1, 2, 3});
+        RotatePDFRequest request = new RotatePDFRequest();
+        request.setFileInput(mockFile);
+        request.setAngle(90);
+
+        PDDocument mockDocument = mock(PDDocument.class);
+        PDPageTree mockPages = mock(PDPageTree.class);
+        PDPage mockPage = mock(PDPage.class);
+
+        when(pdfDocumentFactory.load(request)).thenReturn(mockDocument);
+        when(mockDocument.getPages()).thenReturn(mockPages);
+        when(mockPages.iterator())
+                .thenReturn(java.util.Collections.singletonList(mockPage).iterator());
+        when(mockPage.getRotation()).thenReturn(0);
+
+        // Act
+        ResponseEntity<byte[]> response = rotationController.rotatePDF(request);
+
+        // Assert
+        verify(mockPage).setRotation(90);
+        assertNotNull(response);
+        assertEquals(200, response.getStatusCode().value());
+    }
+
+    @Test
+    public void testRotatePDFInvalidAngle() throws IOException {
+        // Create a mock file
+        MockMultipartFile mockFile =
+                new MockMultipartFile("file", "test.pdf", "application/pdf", new byte[] {1, 2, 3});
+        RotatePDFRequest request = new RotatePDFRequest();
+        request.setFileInput(mockFile);
+        request.setAngle(45); // Invalid angle
+
+        // Act & Assert: Controller direkt aufrufen und Exception erwarten
+        IllegalArgumentException exception =
+                assertThrows(
+                        IllegalArgumentException.class,
+                        () -> rotationController.rotatePDF(request));
+        assertEquals("Angle must be a multiple of 90", exception.getMessage());
+    }
+}