Tests for dashboard.vanity.Router (#536)

We're now up to 54% test coverage!

Jira: OPS-1443

tests/data/apps.yml

@@ -0,0 +1,39 @@
+# Copied a snapshot from https://github.com/mozilla-iam/sso-dashboard-configuration/
+apps:
+- application:
+    authorized_groups:
+    - mozilliansorg_netlify-access
+    authorized_users: []
+    client_id: client-id-for-netlify
+    display: true
+    logo: netlify.png
+    name: Netlify
+    op: auth0
+    url: https://some-url-for-netlify
+    vanity_url:
+    - /netlify
+- application:
+    authorized_groups:
+    - team_moco
+    - team_mofo
+    - team_mzla
+    authorized_users: []
+    display: true
+    logo: accountmanager.png
+    name: Account Portal
+    op: auth0
+    url: https://some-url-for-account-manager
+    vanity_url:
+    - /accountmanager
+- application:
+    authorized_groups:
+    - mozilliansorg_acoustic_production_access
+    authorized_users: []
+    client_id: client-id-for-acoustic
+    display: true
+    logo: acoustic.png
+    name: Acoustic
+    op: auth0
+    url: https://some-url-for-acoustic
+    vanity_url:
+    - /acoustic

tests/test_vanity.py

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+from pathlib import Path
+import pytest
+from flask import Flask
+from dashboard import config
+from dashboard import vanity
+from dashboard.models import tile
+from dashboard.op import yaml_loader
+
+
+@pytest.fixture
+def externals(monkeypatch):
+    # Internal to the way dashboard.models.tile.CDNTransfer works.
+    models_dir = Path(__file__).parent / "models"
+    monkeypatch.setattr("os.path.dirname", lambda _: models_dir)
+    # Internal to how Configs work.
+    monkeypatch.setenv("SSO-DASHBOARD_REDIS_CONNECTOR", "foobar")
+    monkeypatch.setenv("SSO-DASHBOARD_SECRET_KEY", "deadbeef")
+    monkeypatch.setenv("SSO-DASHBOARD_S3_BUCKET", "")
+    monkeypatch.setenv("SSO-DASHBOARD_FORBIDDEN_PAGE_PUBLIC_KEY", "")
+    monkeypatch.setenv("SSO-DASHBOARD_CDN", "https://localhost")
+
+
+@pytest.fixture
+def app_config(externals):
+    return config.Default()
+
+
+@pytest.fixture
+def dashboard_app(app_config):
+    """
+    A mini instance of the app.
+    """
+    app = Flask("dashboard")
+    app.config.from_object(app_config)
+    yield app
+
+
+@pytest.fixture
+def cdn(app_config):
+    return tile.CDNTransfer(app_config)
+
+
+@pytest.fixture
+def client(dashboard_app):
+    return dashboard_app.test_client()
+
+
+class TestVanity:
+    def test_router(self, dashboard_app, cdn, client):
+        router = vanity.Router(dashboard_app, cdn)
+        router.setup()
+        response = client.get("/netlify")
+        assert response.location == "https://some-url-for-netlify", "Did not properly redirect vanity URL"