test: Exchange Rate Revaluation functions and its impact on ledger
diff --git a/erpnext/accounts/doctype/exchange_rate_revaluation/test_exchange_rate_revaluation.py b/erpnext/accounts/doctype/exchange_rate_revaluation/test_exchange_rate_revaluation.py
index ec55e60..ced04ce 100644
--- a/erpnext/accounts/doctype/exchange_rate_revaluation/test_exchange_rate_revaluation.py
+++ b/erpnext/accounts/doctype/exchange_rate_revaluation/test_exchange_rate_revaluation.py
@@ -3,6 +3,296 @@
 
 import unittest
 
+import frappe
+from frappe import qb
+from frappe.tests.utils import FrappeTestCase, change_settings
+from frappe.utils import add_days, flt, today
 
-class TestExchangeRateRevaluation(unittest.TestCase):
-	pass
+from erpnext import get_default_cost_center
+from erpnext.accounts.doctype.payment_entry.payment_entry import get_payment_entry
+from erpnext.accounts.doctype.payment_entry.test_payment_entry import create_payment_entry
+from erpnext.accounts.doctype.purchase_invoice.test_purchase_invoice import make_purchase_invoice
+from erpnext.accounts.doctype.sales_invoice.test_sales_invoice import create_sales_invoice
+from erpnext.accounts.party import get_party_account
+from erpnext.accounts.test.accounts_mixin import AccountsTestMixin
+from erpnext.stock.doctype.item.test_item import create_item
+
+
+class TestExchangeRateRevaluation(AccountsTestMixin, FrappeTestCase):
+	def setUp(self):
+		self.create_company()
+		self.create_usd_receivable_account()
+		self.create_item()
+		self.create_customer()
+		self.clear_old_entries()
+		self.set_system_and_company_settings()
+
+	def tearDown(self):
+		frappe.db.rollback()
+
+	def set_system_and_company_settings(self):
+		# set number and currency precision
+		system_settings = frappe.get_doc("System Settings")
+		system_settings.float_precision = 2
+		system_settings.currency_precision = 2
+		system_settings.save()
+
+		# Using Exchange Gain/Loss account for unrealized as well.
+		company_doc = frappe.get_doc("Company", self.company)
+		company_doc.unrealized_exchange_gain_loss_account = company_doc.exchange_gain_loss_account
+		company_doc.save()
+
+	@change_settings(
+		"Accounts Settings",
+		{"allow_multi_currency_invoices_against_single_party_account": 1, "allow_stale": 0},
+	)
+	def test_01_revaluation_of_forex_balance(self):
+		"""
+		Test Forex account balance and Journal creation post Revaluation
+		"""
+		si = create_sales_invoice(
+			item=self.item,
+			company=self.company,
+			customer=self.customer,
+			debit_to=self.debtors_usd,
+			posting_date=today(),
+			parent_cost_center=self.cost_center,
+			cost_center=self.cost_center,
+			rate=100,
+			price_list_rate=100,
+			do_not_submit=1,
+		)
+		si.currency = "USD"
+		si.conversion_rate = 80
+		si.save().submit()
+
+		err = frappe.new_doc("Exchange Rate Revaluation")
+		err.company = (self.company,)
+		err.posting_date = today()
+		accounts = err.get_accounts_data()
+		err.extend("accounts", accounts)
+		row = err.accounts[0]
+		row.new_exchange_rate = 85
+		row.new_balance_in_base_currency = flt(
+			row.new_exchange_rate * flt(row.balance_in_account_currency)
+		)
+		row.gain_loss = row.new_balance_in_base_currency - flt(row.balance_in_base_currency)
+		err.set_total_gain_loss()
+		err = err.save().submit()
+
+		# Create JV for ERR
+		err_journals = err.make_jv_entries()
+		je = frappe.get_doc("Journal Entry", err_journals.get("revaluation_jv"))
+		je = je.submit()
+
+		je.reload()
+		self.assertEqual(je.voucher_type, "Exchange Rate Revaluation")
+		self.assertEqual(je.total_debit, 8500.0)
+		self.assertEqual(je.total_credit, 8500.0)
+
+		acc_balance = frappe.db.get_all(
+			"GL Entry",
+			filters={"account": self.debtors_usd, "is_cancelled": 0},
+			fields=["sum(debit)-sum(credit) as balance"],
+		)[0]
+		self.assertEqual(acc_balance.balance, 8500.0)
+
+	@change_settings(
+		"Accounts Settings",
+		{"allow_multi_currency_invoices_against_single_party_account": 1, "allow_stale": 0},
+	)
+	def test_02_accounts_only_with_base_currency_balance(self):
+		"""
+		Test Revaluation on Forex account with balance only in base currency
+		"""
+		si = create_sales_invoice(
+			item=self.item,
+			company=self.company,
+			customer=self.customer,
+			debit_to=self.debtors_usd,
+			posting_date=today(),
+			parent_cost_center=self.cost_center,
+			cost_center=self.cost_center,
+			rate=100,
+			price_list_rate=100,
+			do_not_submit=1,
+		)
+		si.currency = "USD"
+		si.conversion_rate = 80
+		si.save().submit()
+
+		pe = get_payment_entry(si.doctype, si.name)
+		pe.source_exchange_rate = 85
+		pe.received_amount = 8500
+		pe.save().submit()
+
+		# Cancel the auto created gain/loss JE to simulate balance only in base currency
+		je = frappe.db.get_all(
+			"Journal Entry Account", filters={"reference_name": si.name}, pluck="parent"
+		)[0]
+		frappe.get_doc("Journal Entry", je).cancel()
+
+		err = frappe.new_doc("Exchange Rate Revaluation")
+		err.company = (self.company,)
+		err.posting_date = today()
+		err.fetch_and_calculate_accounts_data()
+		err = err.save().submit()
+
+		# Create JV for ERR
+		self.assertTrue(err.check_journal_entry_condition())
+		err_journals = err.make_jv_entries()
+		je = frappe.get_doc("Journal Entry", err_journals.get("zero_balance_jv"))
+		je = je.submit()
+
+		je.reload()
+		self.assertEqual(je.voucher_type, "Exchange Gain Or Loss")
+		self.assertEqual(len(je.accounts), 2)
+		# Only base currency fields will be posted to
+		for acc in je.accounts:
+			self.assertEqual(acc.debit_in_account_currency, 0)
+			self.assertEqual(acc.credit_in_account_currency, 0)
+
+		self.assertEqual(je.total_debit, 500.0)
+		self.assertEqual(je.total_credit, 500.0)
+
+		acc_balance = frappe.db.get_all(
+			"GL Entry",
+			filters={"account": self.debtors_usd, "is_cancelled": 0},
+			fields=[
+				"sum(debit)-sum(credit) as balance",
+				"sum(debit_in_account_currency)-sum(credit_in_account_currency) as balance_in_account_currency",
+			],
+		)[0]
+		# account shouldn't have balance in base and account currency
+		self.assertEqual(acc_balance.balance, 0.0)
+		self.assertEqual(acc_balance.balance_in_account_currency, 0.0)
+
+	@change_settings(
+		"Accounts Settings",
+		{"allow_multi_currency_invoices_against_single_party_account": 1, "allow_stale": 0},
+	)
+	def test_03_accounts_only_with_account_currency_balance(self):
+		"""
+		Test Revaluation on Forex account with balance only in account currency
+		"""
+		precision = frappe.db.get_single_value("System Settings", "currency_precision")
+
+		# posting on previous date to make sure that ERR picks up the Payment entry's exchange
+		# rate while calculating gain/loss for account currency balance
+		si = create_sales_invoice(
+			item=self.item,
+			company=self.company,
+			customer=self.customer,
+			debit_to=self.debtors_usd,
+			posting_date=add_days(today(), -1),
+			parent_cost_center=self.cost_center,
+			cost_center=self.cost_center,
+			rate=100,
+			price_list_rate=100,
+			do_not_submit=1,
+		)
+		si.currency = "USD"
+		si.conversion_rate = 80
+		si.save().submit()
+
+		pe = get_payment_entry(si.doctype, si.name)
+		pe.paid_amount = 95
+		pe.source_exchange_rate = 84.211
+		pe.received_amount = 8000
+		pe.references = []
+		pe.save().submit()
+
+		acc_balance = frappe.db.get_all(
+			"GL Entry",
+			filters={"account": self.debtors_usd, "is_cancelled": 0},
+			fields=[
+				"sum(debit)-sum(credit) as balance",
+				"sum(debit_in_account_currency)-sum(credit_in_account_currency) as balance_in_account_currency",
+			],
+		)[0]
+		# account should have balance only in account currency
+		self.assertEqual(flt(acc_balance.balance, precision), 0.0)
+		self.assertEqual(flt(acc_balance.balance_in_account_currency, precision), 5.0)  # in USD
+
+		err = frappe.new_doc("Exchange Rate Revaluation")
+		err.company = (self.company,)
+		err.posting_date = today()
+		err.fetch_and_calculate_accounts_data()
+		err.set_total_gain_loss()
+		err = err.save().submit()
+
+		# Create JV for ERR
+		self.assertTrue(err.check_journal_entry_condition())
+		err_journals = err.make_jv_entries()
+		je = frappe.get_doc("Journal Entry", err_journals.get("zero_balance_jv"))
+		je = je.submit()
+
+		je.reload()
+		self.assertEqual(je.voucher_type, "Exchange Gain Or Loss")
+		self.assertEqual(len(je.accounts), 2)
+		# Only account currency fields will be posted to
+		for acc in je.accounts:
+			self.assertEqual(flt(acc.debit, precision), 0.0)
+			self.assertEqual(flt(acc.credit, precision), 0.0)
+
+		row = [x for x in je.accounts if x.account == self.debtors_usd][0]
+		self.assertEqual(flt(row.credit_in_account_currency, precision), 5.0)  # in USD
+		row = [x for x in je.accounts if x.account != self.debtors_usd][0]
+		self.assertEqual(flt(row.debit_in_account_currency, precision), 421.06)  # in INR
+
+		# total_debit and total_credit will be 0.0, as JV is posting only to account currency fields
+		self.assertEqual(flt(je.total_debit, precision), 0.0)
+		self.assertEqual(flt(je.total_credit, precision), 0.0)
+
+		acc_balance = frappe.db.get_all(
+			"GL Entry",
+			filters={"account": self.debtors_usd, "is_cancelled": 0},
+			fields=[
+				"sum(debit)-sum(credit) as balance",
+				"sum(debit_in_account_currency)-sum(credit_in_account_currency) as balance_in_account_currency",
+			],
+		)[0]
+		# account shouldn't have balance in base and account currency post revaluation
+		self.assertEqual(flt(acc_balance.balance, precision), 0.0)
+		self.assertEqual(flt(acc_balance.balance_in_account_currency, precision), 0.0)
+
+	@change_settings(
+		"Accounts Settings",
+		{"allow_multi_currency_invoices_against_single_party_account": 1, "allow_stale": 0},
+	)
+	def test_04_get_account_details_function(self):
+		si = create_sales_invoice(
+			item=self.item,
+			company=self.company,
+			customer=self.customer,
+			debit_to=self.debtors_usd,
+			posting_date=today(),
+			parent_cost_center=self.cost_center,
+			cost_center=self.cost_center,
+			rate=100,
+			price_list_rate=100,
+			do_not_submit=1,
+		)
+		si.currency = "USD"
+		si.conversion_rate = 80
+		si.save().submit()
+
+		from erpnext.accounts.doctype.exchange_rate_revaluation.exchange_rate_revaluation import (
+			get_account_details,
+		)
+
+		account_details = get_account_details(
+			self.company, si.posting_date, self.debtors_usd, "Customer", self.customer, 0.05
+		)
+		# not checking for new exchange rate and balances as it is dependent on live exchange rates
+		expected_data = {
+			"account_currency": "USD",
+			"balance_in_base_currency": 8000.0,
+			"balance_in_account_currency": 100.0,
+			"current_exchange_rate": 80.0,
+			"zero_balance": False,
+			"new_balance_in_account_currency": 100.0,
+		}
+
+		for key, val in expected_data.items():
+			self.assertEqual(expected_data.get(key), account_details.get(key))