Enhance return details service with error handling and tests.

- ✨ **Feature**: Improved error handling in fetchReturnDetails method
- 🧪 **Test**: Added unit tests for ReturnDetailsService

libs/oms/data-access/src/lib/return-details.service.spec.ts

@@ -0,0 +1,64 @@
+import { createServiceFactory, SpectatorService } from '@ngneat/spectator/jest';
+import { ReturnDetailsService } from './return-details.service';
+import { ReceiptService } from '@generated/swagger/oms-api';
+import { of } from 'rxjs';
+import { FetchReturnDetails } from './schemas';
+import { Receipt } from './models';
+
+describe('ReturnDetailsService', () => {
+  let spectator: SpectatorService<ReturnDetailsService>;
+  const createService = createServiceFactory({
+    service: ReturnDetailsService,
+    mocks: [ReceiptService],
+  });
+
+  beforeEach(() => {
+    spectator = createService();
+  });
+
+  it('should fetch return details successfully', (done) => {
+    // Arrange
+    const mockParams: FetchReturnDetails = { receiptId: 123 };
+    const mockResponse: any = { result: { id: 123, data: 'mockData' } };
+    const receiptService = spectator.inject(ReceiptService);
+    receiptService.ReceiptGetReceipt.mockReturnValue(of(mockResponse));
+
+    // Act
+    spectator.service.fetchReturnDetails(mockParams).subscribe((result) => {
+      // Assert
+      expect(result).toEqual(mockResponse.result as Receipt);
+      done();
+    });
+  });
+
+  it('should throw an error if API response contains an error', (done) => {
+    // Arrange
+    const mockParams: FetchReturnDetails = { receiptId: 123 };
+    const mockResponse: any = { error: 'API error' };
+    const receiptService = spectator.inject(ReceiptService);
+    receiptService.ReceiptGetReceipt.mockReturnValue(of(mockResponse));
+
+    // Act
+    spectator.service.fetchReturnDetails(mockParams).subscribe({
+      error: (err) => {
+        // Assert
+        expect(err.message).toBe('Failed to fetch return details');
+        done();
+      },
+    });
+  });
+
+  it('should throw an error if parameters are invalid', (done) => {
+    // Arrange
+    const invalidParams: any = { receiptId: null };
+
+    // Act
+    spectator.service.fetchReturnDetails(invalidParams).subscribe({
+      error: (err) => {
+        // Assert
+        expect(err).toBeTruthy();
+        done();
+      },
+    });
+  });
+});

libs/oms/data-access/src/lib/return-details.service.ts

@@ -4,10 +4,20 @@ import { map, Observable, throwError } from 'rxjs';
 import { ReceiptService } from '@generated/swagger/oms-api';
 import { Receipt } from './models';
 
+/**
+ * Service responsible for fetching return details for a given receipt.
+ */
 @Injectable({ providedIn: 'root' })
 export class ReturnDetailsService {
   #receiptService = inject(ReceiptService);
 
+  /**
+   * Fetches the return details for a specific receipt.
+   *
+   * @param params - The parameters required to fetch the return details, including the receipt ID.
+   * @returns An observable that emits the fetched receipt details.
+   * @throws Will throw an error if the parameters are invalid or if the API response contains an error.
+   */
   fetchReturnDetails(params: FetchReturnDetails): Observable<Receipt> {
     try {
       const parsed = FetchReturnDetailsSchema.parse(params);
@@ -17,7 +27,7 @@ export class ReturnDetailsService {
         .pipe(
           map((res) => {
             if (res.error || !res.result) {
-              throw new Error('Failed to fetch return details');
+              throw new Error(res.message || 'Failed to fetch return details');
             }
 
             return res.result as Receipt;