Add comprehensive tests for client validation, revenue and expense categories, invoice generation, and schemas

- Implement tests for client validation functions including tax ID, VAT ID, IBAN, BIC, website, and company form validation.
- Create tests for revenue and expense categories ensuring all expected categories and labels are present.
- Add tests for invoice number generation with various scenarios including prefix handling and sequence padding.
- Introduce tests for default categories and their integration, ensuring no overlaps and consistent naming conventions.
- Implement Zod schema validation tests for currency, tax rates, IBAN, tax ID, VAT ID, invoices, companies, and customers.
- Add utility tests for tax calculations, including item amounts and invoice totals, ensuring correct handling of tax rates and formatting.
- Set up Vitest configuration and global test setup for consistent testing environment.

tests/lib/invoice-number.test.ts

@@ -0,0 +1,63 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import prisma from "@/lib/prisma.server";
+import { generateInvoiceNumber } from "@/lib/invoice-number.server";
+
+// Mock the Prisma client
+vi.mock("@/lib/prisma.server", () => ({
+  default: {
+    company: {
+      update: vi.fn(),
+    },
+  },
+}));
+
+describe("invoice-number.server.ts", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("should generate invoice number with year and sequence", async () => {
+    const mockCompany = {
+      invoicePrefix: "RE",
+      invoiceSequence: 5, // Already incremented by Prisma
+    };
+
+    (prisma.company.update as any).mockResolvedValue(mockCompany);
+
+    const result = await generateInvoiceNumber("company-123");
+
+    // invoiceSequence is already 5 (after increment), so we expect 005
+    expect(result).toBe("RE-2026-005");
+    expect(prisma.company.update).toHaveBeenCalledWith({
+      where: { id: "company-123" },
+      data: { invoiceSequence: { increment: 1 } },
+      select: { invoicePrefix: true, invoiceSequence: true },
+    });
+  });
+
+  it("should pad sequence with zeros", async () => {
+    const mockCompany = {
+      invoicePrefix: "RG",
+      invoiceSequence: 2, // Already incremented by Prisma
+    };
+
+    (prisma.company.update as any).mockResolvedValue(mockCompany);
+
+    const result = await generateInvoiceNumber("company-456");
+
+    expect(result).toBe("RG-2026-002");
+  });
+
+  it("should handle custom prefix", async () => {
+    const mockCompany = {
+      invoicePrefix: "INV",
+      invoiceSequence: 10, // Already incremented by Prisma
+    };
+
+    (prisma.company.update as any).mockResolvedValue(mockCompany);
+
+    const result = await generateInvoiceNumber("company-789");
+
+    expect(result).toBe("INV-2026-010");
+  });
+});