test: test files named by their topic, one file per topic

- console settings were split over four files; who sees the form, the
  listen address, and the settings themselves are test_console_settings,
  and who may open a console is test_console_access;
- the three template files are test_templates;
- the quota lock test joins test_quota;
- accounts' test_security_fixes held two topics: the SSH key tests are
  test_ssh_keys, the owner-row delete redirect is in test_views;
- instances' test_security_mutations, who may change a VM, is
  test_permissions.
The suite runs the same 2097 tests.

instances/tests/test_quota.py

@@ -18,6 +18,10 @@ from libvirt import VIR_DOMAIN_PAUSED, VIR_DOMAIN_RUNNING
 from operations.models import Operation
 from vrtManager.util import OperationError
 import socket
+import threading
+import time
+from django.db import connection
+from django.test import Client, TransactionTestCase, override_settings
 
 
 def vm_reader(vcpu=2, memory=1024, disk_gib=10, pending=None):
@@ -292,3 +296,58 @@ class QuotaWithDownHostTestCase(TestCase):
         get_settings()  # app settings are normally loaded by middleware
 
         self.assertEqual(check_user_quota(user, 1, 1, 128, 1), QUOTA_UNVERIFIED)
+
+
+QUOTA_CPUS = 4
+
+
+# Sessions and messages in cookies: concurrent writes to the in-memory test
+# database would fail for reasons unrelated to the quota race.
+@override_settings(
+    SESSION_ENGINE="django.contrib.sessions.backends.signed_cookies",
+    MESSAGE_STORAGE="django.contrib.messages.storage.cookie.CookieStorage",
+)
+
+
+class QuotaRaceTestCase(TransactionTestCase):
+    """Two concurrent resizes of one user's VMs must not both pass the quota."""
+
+    def setUp(self):
+        self.user = get_user_model().objects.create_user("quota_user", password="pw")
+        compute = Compute.objects.create(name="quota-compute", hostname="127.0.0.1", login="", password="", type=4)
+        self.vms = [
+            Instance.objects.create(compute=compute, name=f"quota-vm-{i}", uuid=f"1111111{i}-2222-3333-4444-555555555555")
+            for i in range(2)
+        ]
+        for vm in self.vms:
+            UserInstance.objects.create(user=self.user, instance=vm, is_change=True)
+        self.allocated = 2  # two VMs with one vCPU each
+
+    def fake_quota(self, user, instance, cpu, memory, disk):
+        seen = self.allocated
+        time.sleep(0.3)  # widen the window between the check and the change
+        return "cpu" if seen + cpu > QUOTA_CPUS else ""
+
+    def fake_resize(self, cur_vcpu, vcpu):
+        self.allocated += int(vcpu) - 1
+
+    def resize(self, vm):
+        client = Client()
+        client.force_login(self.user)
+        client.post(reverse("instances:resizevm_cpu", args=[vm.id]), {"vcpu": 3, "cur_vcpu": 3})
+        connection.close()
+
+    def test_second_concurrent_resize_is_refused(self):
+        with patch("instances.views.utils.check_user_quota", self.fake_quota), patch(
+            "instances.models.wvmInstance"
+        ) as wvm:
+            wvm.return_value.get_vcpu.return_value = 1
+            wvm.return_value.instance.isActive.return_value = False  # vCPUs change on a shut-off VM
+            wvm.return_value.resize_cpu.side_effect = self.fake_resize
+            threads = [threading.Thread(target=self.resize, args=(vm,)) for vm in self.vms]
+            for t in threads:
+                t.start()
+            for t in threads:
+                t.join()
+        self.assertEqual(wvm.return_value.resize_cpu.call_count, 1)
+        self.assertLessEqual(self.allocated, QUOTA_CPUS)