feat(core): initial release of SKR03/SKR04 German accounting standards implementation

- Complete implementation of German standard charts of accounts
- SKR03 (Process Structure Principle) for trading/service companies
- SKR04 (Financial Classification Principle) for manufacturing companies
- Double-entry bookkeeping with MongoDB persistence
- Comprehensive reporting suite with DATEV export
- Full TypeScript support and type safety

test/test.skr03.ts

@@ -0,0 +1,159 @@
+import { tap, expect } from '@git.zone/tstest/tapbundle';
+import * as skr from '../ts/index.js';
+
+let api: skr.SkrApi;
+
+tap.test('should initialize SKR03 API', async () => {
+  api = new skr.SkrApi({
+    mongoDbUrl: 'mongodb://localhost:27017',
+    dbName: 'test_skr03',
+  });
+
+  await api.initialize('SKR03');
+  expect(api.getSKRType()).toEqual('SKR03');
+});
+
+tap.test('should have SKR03 accounts initialized', async () => {
+  const accounts = await api.listAccounts();
+  expect(accounts.length).toBeGreaterThan(50);
+
+  // Check specific SKR03 accounts exist
+  const kasse = await api.getAccount('1000');
+  expect(kasse).not.toBeNull();
+  expect(kasse.accountName).toEqual('Kasse');
+  expect(kasse.accountType).toEqual('asset');
+
+  const umsatz = await api.getAccount('4000');
+  expect(umsatz).not.toBeNull();
+  expect(umsatz.accountName).toEqual('Umsatzerlöse');
+  expect(umsatz.accountType).toEqual('revenue');
+});
+
+tap.test('should verify SKR03 process structure principle', async () => {
+  // SKR03 organizes accounts by business process
+  // Class 4: Operating Income
+  // Class 5: Material Costs
+  // Class 6: Personnel Costs
+  // Class 7: Other Operating Expenses
+
+  const class4 = await api.getAccountsByClass(4);
+  expect(class4.length).toBeGreaterThan(0);
+  expect(class4[0].accountType).toEqual('revenue');
+
+  const class5 = await api.getAccountsByClass(5);
+  expect(class5.length).toBeGreaterThan(0);
+  expect(class5[0].accountType).toEqual('expense');
+
+  const class6 = await api.getAccountsByClass(6);
+  expect(class6.length).toBeGreaterThan(0);
+  expect(class6[0].accountType).toEqual('expense');
+});
+
+tap.test('should create custom SKR03 account', async () => {
+  const customAccount = await api.createAccount({
+    accountNumber: '4999',
+    accountName: 'Custom Revenue Account',
+    accountClass: 4,
+    accountType: 'revenue',
+    description: 'Test custom account',
+  });
+
+  expect(customAccount.accountNumber).toEqual('4999');
+  expect(customAccount.skrType).toEqual('SKR03');
+  expect(customAccount.isActive).toBeTrue();
+});
+
+tap.test('should post transaction in SKR03', async () => {
+  const transaction = await api.postTransaction({
+    date: new Date(),
+    debitAccount: '1200', // Bank
+    creditAccount: '4000', // Revenue
+    amount: 1000,
+    description: 'Test sale',
+    reference: 'INV-001',
+    skrType: 'SKR03',
+  });
+
+  expect(transaction.status).toEqual('posted');
+  expect(transaction.amount).toEqual(1000);
+  expect(transaction.skrType).toEqual('SKR03');
+});
+
+tap.test('should post journal entry in SKR03', async () => {
+  const journalEntry = await api.postJournalEntry({
+    date: new Date(),
+    description: 'Test journal entry',
+    reference: 'JE-001',
+    lines: [
+      { accountNumber: '1000', debit: 500 }, // Cash
+      { accountNumber: '1200', debit: 500 }, // Bank
+      { accountNumber: '4000', credit: 1000 }, // Revenue
+    ],
+    skrType: 'SKR03',
+  });
+
+  expect(journalEntry.status).toEqual('posted');
+  expect(journalEntry.isBalanced).toBeTrue();
+  expect(journalEntry.totalDebits).toEqual(1000);
+  expect(journalEntry.totalCredits).toEqual(1000);
+});
+
+tap.test('should generate trial balance for SKR03', async () => {
+  const trialBalance = await api.generateTrialBalance();
+
+  expect(trialBalance.skrType).toEqual('SKR03');
+  expect(trialBalance.entries.length).toBeGreaterThan(0);
+  expect(trialBalance.isBalanced).toBeTrue();
+  expect(trialBalance.totalDebits).toEqual(trialBalance.totalCredits);
+});
+
+tap.test('should generate income statement for SKR03', async () => {
+  const incomeStatement = await api.generateIncomeStatement();
+
+  expect(incomeStatement.skrType).toEqual('SKR03');
+  expect(incomeStatement.revenue.length).toBeGreaterThanOrEqual(0);
+  expect(incomeStatement.expenses.length).toBeGreaterThanOrEqual(0);
+  expect(incomeStatement.netIncome).toEqual(
+    incomeStatement.totalRevenue - incomeStatement.totalExpenses,
+  );
+});
+
+tap.test('should generate balance sheet for SKR03', async () => {
+  const balanceSheet = await api.generateBalanceSheet();
+
+  expect(balanceSheet.skrType).toEqual('SKR03');
+  expect(balanceSheet.assets.totalAssets).toBeGreaterThanOrEqual(0);
+  expect(balanceSheet.isBalanced).toBeTrue();
+});
+
+tap.test('should search accounts in SKR03', async () => {
+  const results = await api.searchAccounts('Bank');
+
+  expect(results.length).toBeGreaterThan(0);
+  const bankAccount = results.find((a) => a.accountNumber === '1200');
+  expect(bankAccount).not.toBeNull();
+});
+
+tap.test('should export SKR03 accounts to CSV', async () => {
+  const csv = await api.exportAccountsToCSV();
+
+  expect(csv).toInclude('"Account";"Name";"Description";"Type";"Active"');
+  expect(csv).toInclude('1000');
+  expect(csv).toInclude('Kasse');
+});
+
+tap.test('should close API connection', async () => {
+  await api.close();
+
+  // Verify API requires reinitialization
+  let errorThrown = false;
+  try {
+    await api.listAccounts();
+  } catch (error) {
+    errorThrown = true;
+    expect(error.message).toInclude('not initialized');
+  }
+  expect(errorThrown).toBeTrue();
+});
+
+export default tap.start();