completed the product-invory.js and the unit tests realted to it

.gitignore

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+node_modules
+package-lock.json

product-inventory/package.json

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+{
+  "name": "product-inventory",
+  "version": "1.0.0",
+  "main": "index.js",
+  "scripts": {
+    "test": "jest"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "description": "",
+  "devDependencies": {
+    "jest": "^29.7.0"
+  }
+}

product-inventory/products.js

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+function calculateDiscount(price, discountRate) {
+    if (typeof price !== 'number' || typeof discountRate !== 'number') return null;
+    if (discountRate < 0 || discountRate > 1) return null;
+    // TODO: Implement logic
+    const discount = price *(1-discountRate);
+    return discount;
+}
+
+function filterProducts(products, callback) {
+    if (!Array.isArray(products) || typeof callback !== 'function') return [];
+    // TODO: Implement filtering logic
+
+    return products.filter(callback);
+}
+
+function sortInventory(inventory, key) {
+    if (!Array.isArray(inventory) || typeof key !== 'string') return [];
+    // TODO: Implement sorting logic
+    const sortedArray = [...inventory].sort((a,b) =>a[key] - b[key]);
+    return sortedArray;
+}
+
+
+module.exports = {
+    calculateDiscount : calculateDiscount,
+    filterProducts : filterProducts,
+    sortInventory : sortInventory
+}

product-inventory/tests/products.test.js

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+const products = require('../products.js');
+
+let inventory = [
+    {item : "peach", price : 10},
+    {item : "apple", price : 2},
+    {item : "orange", price : 3},
+    {item : "banana" , price : 4}
+];
+
+
+
+describe("calculate Discount", ()=>{
+    test("applies a valid discount rate", () => {
+        expect(products.calculateDiscount(100, 0.1)).toBe(90);
+    });
+
+    test("handles an invalid discount rate gracefully", () => {
+        expect(products.calculateDiscount(100, -0.1)).toBe(null);
+    });
+
+    test("handles edge case with price of 0", () => {
+        expect(products.calculateDiscount(0, 0.2)).toBe(0);
+    });
+});
+
+describe("filter products", ()=>{
+     test("filter products based on callback", ()=>{
+        const filtered = products.filterProducts(inventory, product => product.price >1 )
+        expect(filtered).toEqual([
+            {item : "peach", price : 10},
+            {item : "apple", price : 2},
+            {item : "orange", price : 3},
+            {item : "banana" , price : 4},
+
+        ])
+     });
+
+     test("returns empty array if products is not an array ", ()=>{
+        expect(products.filterProducts("invalid",product => product.price >1)).toEqual([]);
+     });
+
+     test("return empty array if no products match",()=>{
+        expect(products.filterProducts(inventory, product => product.price ==1)).toEqual([]);
+     });
+
+     test("returns empty array if callback is not a function", ()=>{
+        expect(products.filterProducts(inventory,"not a function")).toEqual([]);
+     });
+
+
+});
+
+describe("sortInventory", ()=>{
+
+    test("sorts the inventory by price in ascending order", ()=>{
+
+        expect(products.sortInventory(inventory,"price")).toEqual([
+            {item : "apple", price : 2},
+            {item : "orange", price : 3},
+            {item : "banana", price : 4},
+            {item : "peach", price : 10}
+          ]);
+
+    });
+
+    test("returns an empty array for invalid inventory",()=>{
+        expect(products.sortInventory("nothing","price")).toEqual([])
+    });
+
+    test("returns an empty array for invalid key",()=>{
+
+        expect(products.sortInventory(inventory,123)).toEqual([])
+    });
+
+});