diff --git a/app/apps/mini_tools/tests.py b/app/apps/mini_tools/tests.py
index 7ce503c2..e2227048 100644
--- a/app/apps/mini_tools/tests.py
+++ b/app/apps/mini_tools/tests.py
@@ -1,3 +1,129 @@
-from django.test import TestCase
+from datetime import date
+from decimal import Decimal
+from unittest.mock import patch
 
-# Create your tests here.
+from django.contrib.auth import get_user_model
+from django.test import TestCase, override_settings
+from django.urls import reverse
+from django.utils import timezone
+
+from apps.accounts.models import Account, AccountGroup
+from apps.common.middleware.thread_local import delete_current_user, write_current_user
+from apps.currencies.models import Currency, ExchangeRate
+from apps.mini_tools.utils.simulator import get_simulator_baseline
+from apps.transactions.models import Transaction
+
+
+@override_settings(
+    STORAGES={
+        "default": {"BACKEND": "django.core.files.storage.FileSystemStorage"},
+        "staticfiles": {
+            "BACKEND": "django.contrib.staticfiles.storage.StaticFilesStorage"
+        },
+    },
+    WHITENOISE_AUTOREFRESH=True,
+)
+@patch(
+    "apps.mini_tools.utils.simulator.timezone.localdate",
+    return_value=date(2026, 3, 15),
+)
+class SimulatorTests(TestCase):
+    def setUp(self):
+        User = get_user_model()
+        self.user = User.objects.create_user(
+            email="testuser@test.com", password="testpass123"
+        )
+        self.client.login(username="testuser@test.com", password="testpass123")
+        write_current_user(self.user)
+
+        self.currency = Currency.objects.create(
+            code="USD", name="US Dollar", decimal_places=2, prefix="$ "
+        )
+        group = AccountGroup.objects.create(name="Group")
+        self.account = Account.objects.create(
+            name="Checking", group=group, currency=self.currency
+        )
+
+    def tearDown(self):
+        delete_current_user()
+
+    def _transaction(self, type, amount, reference_date, is_paid=True, account=None):
+        return Transaction.objects.create(
+            account=account or self.account,
+            type=type,
+            is_paid=is_paid,
+            date=reference_date,
+            reference_date=reference_date,
+            amount=Decimal(amount),
+            description="Test",
+            owner=self.user,
+        )
+
+    def _currency(self, baseline):
+        return next(c for c in baseline["currencies"] if c["id"] == self.currency.id)
+
+    def test_baseline_monthly_projection(self, _):
+        self._transaction(Transaction.Type.INCOME, "1000", date(2026, 1, 1))
+        self._transaction(Transaction.Type.EXPENSE, "200", date(2026, 2, 1), False)
+        self._transaction(Transaction.Type.INCOME, "500", date(2026, 3, 1), False)
+        self._transaction(Transaction.Type.EXPENSE, "50", date(2026, 3, 1))
+        self._transaction(Transaction.Type.EXPENSE, "100", date(2031, 5, 1), False)
+
+        baseline = get_simulator_baseline(self.user)
+        currency = self._currency(baseline)
+
+        self.assertEqual(baseline["current_month"], "2026-03")
+        self.assertEqual(
+            currency["monthly"],
+            {"2026-01": 1000.0, "2026-02": -200.0, "2026-03": 450.0, "2031-05": -100.0},
+        )
+        self.assertIsNone(currency["exchange"])
+
+    def test_baseline_ignores_archived_and_untracked_accounts(self, _):
+        group = AccountGroup.objects.create(name="Other")
+        archived = Account.objects.create(
+            name="Old", group=group, currency=self.currency, is_archived=True
+        )
+        untracked = Account.objects.create(
+            name="Hidden", group=group, currency=self.currency
+        )
+        untracked.untracked_by.add(self.user)
+
+        self._transaction(Transaction.Type.INCOME, "100", date(2026, 3, 1))
+        self._transaction(
+            Transaction.Type.INCOME, "1000", date(2026, 3, 1), account=archived
+        )
+        self._transaction(
+            Transaction.Type.INCOME, "1000", date(2026, 3, 1), account=untracked
+        )
+
+        currency = self._currency(get_simulator_baseline(self.user))
+
+        self.assertEqual(currency["monthly"], {"2026-03": 100.0})
+
+    def test_baseline_exchange_rate(self, _):
+        euro = Currency.objects.create(
+            code="EUR", name="Euro", decimal_places=2, suffix=" EUR"
+        )
+        self.currency.exchange_currency = euro
+        self.currency.save()
+        ExchangeRate.objects.create(
+            from_currency=self.currency,
+            to_currency=euro,
+            rate=Decimal("0.5"),
+            date=timezone.now(),
+        )
+
+        currency = self._currency(get_simulator_baseline(self.user))
+
+        self.assertEqual(
+            currency["exchange"],
+            {"rate": 0.5, "prefix": "", "suffix": " EUR", "decimal_places": 2},
+        )
+
+    def test_simulator_view_renders(self, _):
+        response = self.client.get(reverse("simulator"))
+
+        self.assertEqual(response.status_code, 200)
+        self.assertContains(response, 'id="simulator-baseline"')
+        self.assertContains(response, "sim-start")