Add test case when switching to no currency.

This ensure that bill's converted amounts are not converted in this case
Since all bills must have the same currency, the logical algorithm for
a human brain is simply to strip the currency,
and keep the original amount.

ihatemoney/tests/budget_test.py

@@ -1614,6 +1614,56 @@ class BudgetTestCase(IhatemoneyTestCase):
         bill = project.get_bills().first()
         assert bill.converted_amount == bill.amount
 
+    def test_currency_switch_to_no_currency(self):
+
+        mock_data = {"USD": 1, "EUR": 0.8, "CAD": 1.2, CurrencyConverter.no_currency: 1}
+        converter = CurrencyConverter()
+        converter.get_rates = MagicMock(return_value=mock_data)
+
+        # Default currency is 'XXX', but we should start from a project with a currency
+        self.post_project("raclette", default_currency="USD")
+
+        # add members
+        self.client.post("/raclette/members/add", data={"name": "zorglub"})
+        self.client.post("/raclette/members/add", data={"name": "fred"})
+
+        # Bills with a different currency than project's default
+        self.client.post(
+            "/raclette/add",
+            data={
+                "date": "2016-12-31",
+                "what": "fromage à raclette",
+                "payer": 1,
+                "payed_for": [1, 2],
+                "amount": "10.0",
+                "original_currency": "EUR",
+            },
+        )
+
+        self.client.post(
+            "/raclette/add",
+            data={
+                "date": "2017-01-01",
+                "what": "aspirine",
+                "payer": 2,
+                "payed_for": [1, 2],
+                "amount": "5.0",
+                "original_currency": "EUR",
+            },
+        )
+
+        project = models.Project.query.get("raclette")
+
+        for bill in project.get_bills_unordered():
+            assert bill.converted_amount == converter.exchange_currency(
+                bill.amount, "EUR", "USD"
+            )
+
+        # And switch project to no currency: amount should be equal to what was submitted
+        project.switch_currency(converter.no_currency)
+        no_currency_bills = [(bill.amount, bill.converted_amount) for bill in project.get_bills()]
+        assert no_currency_bills == [(5.0, 5.0), (10.0, 10.0)]
+
 
 if __name__ == "__main__":
     unittest.main()