add py.test setup with support for coverage

.gitignore

@@ -37,3 +37,4 @@ nosetests.xml
 .vagrant
 #local settings
 treeherder/settings/local.py
+htmlcov/

runtests.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+py.test tests/$* --cov-report html --cov treeherder

tests/conftest.py

@@ -0,0 +1,66 @@
+import os
+
+
+def pytest_sessionstart(session):
+    """
+Set up the test environment.
+
+Set DJANGO_SETTINGS_MODULE and sets up a test database.
+
+"""
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "treeherder.settings.base")
+
+    from django.conf import settings
+    from django.test.simple import DjangoTestSuiteRunner
+    # we don't actually let Django run the tests, but we need to use some
+    # methods of its runner for setup/teardown of dbs and some other things
+    session.django_runner = DjangoTestSuiteRunner()
+    # this provides templates-rendered debugging info and locmem mail storage
+    session.django_runner.setup_test_environment()
+    # support custom db prefix for tests for the main datazilla datasource
+    # as well as for the testproj and testpushlog dbs
+    prefix = getattr(settings, "TEST_DB_PREFIX", "")
+    settings.DATABASES["default"]["TEST_NAME"] = "{0}test_treeherder".format(prefix)
+    # this sets up a clean test-only database
+    session.django_db_config = session.django_runner.setup_databases()
+
+
+def pytest_sessionfinish(session):
+    """Tear down the test environment, including databases."""
+    print("\n")
+
+    session.django_runner.teardown_databases(session.django_db_config)
+    session.django_runner.teardown_test_environment()
+
+
+def pytest_runtest_setup(item):
+    """
+Per-test setup.
+
+Start a transaction and disable transaction methods for the duration of the
+test. The transaction will be rolled back after the test. This prevents any
+database changes made to Django ORM models from persisting between tests,
+providing test isolation.
+
+"""
+    from django.test.testcases import disable_transaction_methods
+    from django.db import transaction
+
+    transaction.enter_transaction_management()
+    transaction.managed(True)
+    disable_transaction_methods()
+
+
+def pytest_runtest_teardown(item):
+    """
+Per-test teardown.
+
+Roll back the Django ORM transaction
+
+"""
+    from django.test.testcases import restore_transaction_methods
+    from django.db import transaction
+
+    restore_transaction_methods()
+    transaction.rollback()
+    transaction.leave_transaction_management()