diff --git a/src/Product.test.ts b/src/Product.test.ts
index 847d926..597d59a 100644
--- a/src/Product.test.ts
+++ b/src/Product.test.ts
@@ -1,8 +1,30 @@
 import { Product } from "./Product";
 import { MockSpreadsheetService } from "./services/MockSpreadsheetService";
+import { MockShop } from "./test/MockShop";
+
+// Mock Config class to avoid GAS usage
+jest.mock("./config", () => {
+  return {
+    Config: jest.fn().mockImplementation(() => {
+      return {
+        productPhotosFolderId: "mock-folder-id",
+        shopifyApiKey: "mock-key",
+        shopifyApiSecretKey: "mock-secret",
+        shopifyAdminApiAccessToken: "mock-token",
+        shopifyApiURI: "mock-uri",
+        shopifyStorePublicationId: "mock-pub-id",
+        shopifyLocationId: "mock-loc-id",
+        shopifyCountryCodeOfOrigin: "US",
+        shopifyProvinceCodeOfOrigin: "CA",
+        salesSyncFrequency: 10
+      };
+    })
+  };
+});
 
 describe("Product", () => {
   let mockService: MockSpreadsheetService;
+  let mockShop: MockShop;
 
   beforeEach(() => {
     // Setup mock data
@@ -16,6 +38,7 @@ describe("Product", () => {
         productData
       ]
     });
+    mockShop = new MockShop();
   });
 
   it("should load data from inventory sheet using service", () => {
@@ -32,4 +55,167 @@ describe("Product", () => {
       new Product("NON-EXISTENT-SKU", mockService);
     }).toThrow("product sku 'NON-EXISTENT-SKU' not found in product_inventory");
   });
+
+  it("should skip placeholder values (?)", () => {
+    mockService.setSheetData("product_inventory", [
+        ["sku", "title", "price"],
+        ["TEST-SKU-2", "Original Title", 20.00]
+    ]);
+    const product = new Product("TEST-SKU-2", mockService);
+
+    // Simulate edit with placeholder
+    mockService.setSheetData("product_inventory", [
+        ["sku", "title", "price"],
+        ["TEST-SKU-2", "?", 25.00]
+    ]);
+
+    // Create new instance to trigger import
+    const updatedProduct = new Product("TEST-SKU-2", mockService);
+
+    // Title should be empty (default) because (?) means skip,
+    // BUT Product.ts logic says: if value is "?", continue.
+    // The Product class properties are initialized to defaults (e.g. title="").
+    // If import finds "?", it continues loop, so title remains "".
+    expect(updatedProduct.title).toBe("");
+    expect(updatedProduct.price).toBe(25.00);
+  });
+
+  it("should ignore properties not in class", () => {
+    mockService.setSheetData("product_inventory", [
+        ["sku", "title", "unknown_col"],
+        ["TEST-SKU-3", "Title 3", "some value"]
+    ]);
+    const product = new Product("TEST-SKU-3", mockService);
+    expect((product as any).unknown_col).toBeUndefined();
+    expect(product.title).toBe("Title 3");
+  });
+  it("should map fields correctly to ShopifyProductSet", () => {
+    mockService.setSheetData("product_inventory", [
+        ["sku", "title", "tags", "description", "product_type", "price", "compare_at_price"],
+        ["TEST-SKU-4", "Mapper Test", "tag1, tag2", "<p>Desc</p>", "Type B", 50.00, 60.00]
+    ]);
+    mockService.setSheetData("values", [
+        ["product_type", "shopify_category", "ebay_category_id"],
+        ["Type B", "Shopify Cat B", "Ebay Cat B"]
+    ]);
+
+    const product = new Product("TEST-SKU-4", mockService);
+    product.shopify_status = "ACTIVE"; // Simulate status set
+
+    const sps = product.ToShopifyProductSet();
+
+    expect(sps.title).toBe("Mapper Test");
+    expect(sps.tags).toBe("tag1, tag2");
+    expect(sps.descriptionHtml).toBe("<p>Desc</p>");
+    expect(sps.productType).toBe("Type B");
+    expect(sps.category).toBe("Shopify Cat B");
+    expect(sps.status).toBe("ACTIVE");
+    expect((sps as any).handle).toBe("TEST-SKU-4");
+
+    expect(sps.variants[0].price).toBe(50.00);
+    expect(sps.variants[0].compareAtPrice).toBe(60.00);
+  });
+
+  it("should create new product in Shopify if ID not present", () => {
+    // Setup data
+    mockService.setSheetData("product_inventory", [
+        ["sku", "title", "weight_grams", "shopify_id", "product_type", "photos"],
+        ["TEST-NEW-1", "New Prod", "500", "", "Type A", ""]
+    ]);
+
+    // Mock Config
+    // Note: Config is instantiated inside Product.ts using new Config().
+    // Since we cannot mock the constructor easily without DI, and Product.ts imports Config directly,
+    // we rely on the fact that Config reads from sheet "vars".
+    mockService.setSheetData("vars", [
+        ["key", "value"],
+        ["shopifyLocationId", "loc_123"],
+        ["shopifyCountryCodeOfOrigin", "US"],
+        ["shopifyProvinceCodeOfOrigin", "CA"]
+    ]);
+    mockService.setSheetData("values", [
+        ["product_type", "shopify_category", "ebay_category_id"],
+        ["Type A", "Category A", "123"]
+    ]);
+
+    const product = new Product("TEST-NEW-1", mockService);
+
+    // Mock Shop responses
+    // 1. MatchToShopifyProduct (GetProductBySku) -> returns empty/null
+    mockShop.mockProductBySku = {};
+
+    // 2. productSet mutation
+    // already mocked in MockShop.shopifyGraphQLAPI to return { product: { id: "mock-new-id" } }
+
+    // 3. GetInventoryItemBySku loop
+    // Needs to return item with ID.
+    // MockShop.GetInventoryItemBySku returns { id: "mock-inv-id" }
+
+    product.UpdateShopifyProduct(mockShop);
+
+    // Verify interactions
+    // 1. Match called (GetProductBySku)
+    expect(mockShop.getProductBySkuCalledWith).toBe("TEST-NEW-1");
+
+    // 2. productSet called
+    expect(mockShop.productSetCalledWith).toBeTruthy();
+    const sps = mockShop.productSetCalledWith.variables.productSet;
+    expect(sps.title).toBe("New Prod");
+    expect(sps.handle).toBe("TEST-NEW-1");
+
+    // 3. shopify_id updated in object and sheet
+    expect(product.shopify_id).toBe("mock-new-id");
+    const updatedId = mockService.getCellValueByColumnName("product_inventory", 2, "shopify_id");
+    expect(updatedId).toBe("mock-new-id");
+  });
+
+  it("should update existing product using ID", () => {
+    // Setup data with ID
+    mockService.setSheetData("product_inventory", [
+        ["sku", "title", "weight_grams", "shopify_id", "product_type", "photos"],
+        ["TEST-EXISTING-1", "Updated Title", "1000", "123456", "Type A", ""]
+    ]);
+    mockService.setSheetData("vars", [
+        ["key", "value"],
+        ["shopifyLocationId", "loc_123"],
+        ["shopifyCountryCodeOfOrigin", "US"],
+        ["shopifyProvinceCodeOfOrigin", "CA"]
+    ]);
+    mockService.setSheetData("values", [
+        ["product_type", "shopify_category", "ebay_category_id"],
+        ["Type A", "Category A", "123"]
+    ]);
+
+    const product = new Product("TEST-EXISTING-1", mockService);
+
+    // Mock Shop Match
+    // MatchToShopifyProduct called -> check ID -> GetProductById
+    mockShop.mockProductById = {
+        id: "123456",
+        title: "Old Title",
+        variants: { nodes: [{ id: "gid://shopify/ProductVariant/123456", sku: "TEST-EXISTING-1" }] },
+        options: [{ id: "opt1", optionValues: [{ id: "optval1" }] }]
+    };
+
+    // Mock Shop Update
+    // productSet mutation
+    mockShop.mockResponse = {
+        productSet: {
+            product: { id: "123456" }
+        }
+    };
+    // GetInventoryItem -> returns item
+    mockShop.setInventoryItemCalledWith = null; // spy
+
+    product.UpdateShopifyProduct(mockShop);
+
+    // Verify Match Used ID
+    expect(mockShop.getProductByIdCalledWith).toBe("123456");
+
+    // Verify Update Payload
+    expect(mockShop.productSetCalledWith).toBeTruthy();
+    const sps = mockShop.productSetCalledWith.variables.productSet;
+    expect(sps.title).toBe("Updated Title"); // Should use new title from sheet
+    expect(sps.id).toBe("123456"); // Should include ID to update
+  });
 });
diff --git a/src/services/MockSpreadsheetService.ts b/src/services/MockSpreadsheetService.ts
index 988925e..08809db 100644
--- a/src/services/MockSpreadsheetService.ts
+++ b/src/services/MockSpreadsheetService.ts
@@ -81,7 +81,8 @@ export class MockSpreadsheetService implements ISpreadsheetService {
     const colIndex = headers.indexOf(columnName);
 
     if (colIndex === -1) return null;
-    if (row > data.length) return null;
+    if (colIndex === -1) return null;
+    if (row > data.length || row < 1) return null;
 
     return data[row - 1][colIndex];
   }
diff --git a/src/test/MockShop.ts b/src/test/MockShop.ts
index 04c9d40..7a43910 100644
--- a/src/test/MockShop.ts
+++ b/src/test/MockShop.ts
@@ -8,6 +8,7 @@ export class MockShop implements IShop {
   public getProductByIdCalledWith: string | null = null;
   public productSetCalledWith: any | null = null;
   public shopifyGraphQLAPICalledWith: any | null = null;
+  public setInventoryItemCalledWith: any | null = null;
 
   public mockProductBySku: any = null;
   public mockProductById: any = null;
diff --git a/src/test/setup.ts b/src/test/setup.ts
index 3f953f1..e9d2f12 100644
--- a/src/test/setup.ts
+++ b/src/test/setup.ts
@@ -31,3 +31,15 @@ global.Logger = {
 global.Utilities = {
   formatDate: () => "2025-01-01",
 } as any;
+
+global.DriveApp = {
+  getFolderById: (id: string) => ({
+    getFoldersByName: (name: string) => ({
+      hasNext: () => false,
+      next: () => ({ getUrl: () => "http://mock-drive-url" })
+    }),
+    createFolder: (name: string) => ({
+      getUrl: () => "http://mock-drive-url"
+    }),
+  }),
+} as any;