Add tests for portfolio funding route

This adds a helper to grab a template's context. Using a helper from the
Flask documentation: http://flask.pocoo.org/docs/1.0/signals/?highlight=template_rendered#subscribing-to-signals

tests/routes/portfolios/test_task_orders.py

@@ -0,0 +1,62 @@
+from flask import url_for
+import pytest
+
+from tests.factories import (
+    PortfolioFactory,
+    TaskOrderFactory,
+    random_future_date,
+    random_past_date,
+)
+from tests.utils import captured_templates
+
+
+class TestPortfolioFunding:
+    def test_unfunded_portfolio(self, app, user_session):
+        portfolio = PortfolioFactory.create()
+        user_session(portfolio.owner)
+
+        with captured_templates(app) as templates:
+            response = app.test_client().get(
+                url_for("portfolios.portfolio_funding", portfolio_id=portfolio.id)
+            )
+
+            assert response.status_code == 200
+            _, context = templates[0]
+            assert context["funding_end_date"] is None
+            assert context["total_balance"] == 0
+            assert context["pending_task_orders"] == []
+            assert context["active_task_orders"] == []
+            assert context["expired_task_orders"] == []
+
+    def test_funded_portfolio(self, app, user_session):
+        portfolio = PortfolioFactory.create()
+        user_session(portfolio.owner)
+
+        pending_to = TaskOrderFactory.create(portfolio=portfolio)
+        active_to1 = TaskOrderFactory.create(
+            portfolio=portfolio,
+            start_date=random_past_date(),
+            end_date=random_future_date(),
+            number="42",
+        )
+        active_to2 = TaskOrderFactory.create(
+            portfolio=portfolio,
+            start_date=random_past_date(),
+            end_date=random_future_date(),
+            number="43",
+        )
+        end_date = (
+            active_to1.end_date
+            if active_to1.end_date > active_to2.end_date
+            else active_to2.end_date
+        )
+
+        with captured_templates(app) as templates:
+            response = app.test_client().get(
+                url_for("portfolios.portfolio_funding", portfolio_id=portfolio.id)
+            )
+
+            assert response.status_code == 200
+            _, context = templates[0]
+            assert context["funding_end_date"] is end_date
+            assert context["total_balance"] == active_to1.budget + active_to2.budget