Initial commit: Complete Shopify Price Updater implementation

- Full Node.js application with Shopify GraphQL API integration
- Compare At price support for promotional pricing
- Comprehensive error handling and retry logic
- Progress tracking with markdown logging
- Complete test suite with unit and integration tests
- Production-ready with proper exit codes and signal handling

test-price-utils.js

@@ -0,0 +1,66 @@
+// Quick test script for price utilities
+const {
+	calculateNewPrice,
+	isValidPrice,
+	formatPrice,
+	calculatePercentageChange,
+	isValidPercentage,
+} = require("./src/utils/price.js");
+
+console.log("Testing Price Utilities...\n");
+
+// Test calculateNewPrice
+console.log("=== Testing calculateNewPrice ===");
+try {
+	console.log("10% increase on $100:", calculateNewPrice(100, 10)); // Should be 110
+	console.log("20% decrease on $50:", calculateNewPrice(50, -20)); // Should be 40
+	console.log("5.5% increase on $29.99:", calculateNewPrice(29.99, 5.5)); // Should be 31.64
+	console.log("0% change on $25:", calculateNewPrice(25, 0)); // Should be 25
+	console.log("Zero price with 10% increase:", calculateNewPrice(0, 10)); // Should be 0
+} catch (error) {
+	console.error("Error:", error.message);
+}
+
+// Test edge cases
+console.log("\n=== Testing Edge Cases ===");
+try {
+	console.log("Negative price test (should throw error):");
+	calculateNewPrice(-10, 10);
+} catch (error) {
+	console.log("✓ Correctly caught negative price error:", error.message);
+}
+
+try {
+	console.log("Large decrease test (should throw error):");
+	calculateNewPrice(10, -150); // 150% decrease would make price negative
+} catch (error) {
+	console.log("✓ Correctly caught negative result error:", error.message);
+}
+
+// Test validation functions
+console.log("\n=== Testing Validation Functions ===");
+console.log("isValidPrice(100):", isValidPrice(100)); // true
+console.log("isValidPrice(-10):", isValidPrice(-10)); // false
+console.log('isValidPrice("abc"):', isValidPrice("abc")); // false
+console.log("isValidPrice(0):", isValidPrice(0)); // true
+
+console.log("isValidPercentage(10):", isValidPercentage(10)); // true
+console.log("isValidPercentage(-20):", isValidPercentage(-20)); // true
+console.log('isValidPercentage("abc"):', isValidPercentage("abc")); // false
+
+// Test formatting
+console.log("\n=== Testing Price Formatting ===");
+console.log("formatPrice(29.99):", formatPrice(29.99)); // "29.99"
+console.log("formatPrice(100):", formatPrice(100)); // "100.00"
+console.log("formatPrice(0):", formatPrice(0)); // "0.00"
+
+// Test percentage change calculation
+console.log("\n=== Testing Percentage Change Calculation ===");
+console.log("Change from $100 to $110:", calculatePercentageChange(100, 110)); // 10
+console.log("Change from $50 to $40:", calculatePercentageChange(50, 40)); // -20
+console.log(
+	"Change from $29.99 to $31.64:",
+	calculatePercentageChange(29.99, 31.64)
+); // ~5.5
+
+console.log("\n✓ All tests completed!");