def run_tests(self):
        from django.conf import settings
        from django.core.db import db
        from django.core import management, meta

        # Manually set INSTALLED_APPS to point to the test app.
        settings.INSTALLED_APPS = (APP_NAME,)

        # Determine which models we're going to test.
        test_models = get_test_models()
        if self.which_tests:
            # Only run the specified tests.
            bad_models = [m for m in self.which_tests if m not in test_models]
            if bad_models:
                sys.stderr.write("Models not found: %s\n" % bad_models)
                sys.exit(1)
            else:
                test_models = self.which_tests

        self.output(0, "Running tests with database %r" % settings.DATABASE_ENGINE)

        # If we're using SQLite, it's more convenient to test against an
        # in-memory database.
        if settings.DATABASE_ENGINE == "sqlite3":
            global TEST_DATABASE_NAME
            TEST_DATABASE_NAME = ":memory:"
        else:
            # Create the test database and connect to it. We need autocommit()
            # because PostgreSQL doesn't allow CREATE DATABASE statements
            # within transactions.
            cursor = db.cursor()
            try:
                db.connection.autocommit(1)
            except AttributeError:
                pass
            self.output(1, "Creating test database")
            try:
                cursor.execute("CREATE DATABASE %s" % TEST_DATABASE_NAME)
            except:
                confirm = raw_input("The test database, %s, already exists. Type 'yes' to delete it, or 'no' to cancel: " % TEST_DATABASE_NAME)
                if confirm == 'yes':
                    cursor.execute("DROP DATABASE %s" % TEST_DATABASE_NAME)
                    cursor.execute("CREATE DATABASE %s" % TEST_DATABASE_NAME)
                else:
                    print "Tests cancelled."
                    return
        db.close()
        old_database_name = settings.DATABASE_NAME
        settings.DATABASE_NAME = TEST_DATABASE_NAME

        # Initialize the test database.
        cursor = db.cursor()
        self.output(1, "Initializing test database")
        management.init()

        # Run the tests for each test model.
        self.output(1, "Running app tests")
        for model_name in test_models:
            self.output(1, "%s model: Importing" % model_name)
            try:
                mod = meta.get_app(model_name)
            except Exception, e:
                log_error(model_name, "Error while importing", ''.join(traceback.format_exception(*sys.exc_info())[1:]))
                continue
            self.output(1, "%s model: Installing" % model_name)
            management.install(mod)

            # Run the API tests.
            p = doctest.DocTestParser()
            test_namespace = dict([(m._meta.module_name, getattr(mod, m._meta.module_name)) for m in mod._MODELS])
            dtest = p.get_doctest(mod.API_TESTS, test_namespace, model_name, None, None)
            # Manually set verbose=False, because "-v" command-line parameter
            # has side effects on doctest TestRunner class.
            runner = DjangoDoctestRunner(verbosity_level=verbosity_level, verbose=False)
            self.output(1, "%s model: Running tests" % model_name)
            try:
                runner.run(dtest, clear_globs=True, out=sys.stdout.write)
            finally:
                # Rollback, in case of database errors. Otherwise they'd have
                # side effects on other tests.
                db.rollback()
                    self.output(1, "%s module: running tests" % module)
                    runner.run(dtest, clear_globs=True, out=sys.stdout.write)
                if hasattr(mod, "run_tests") and callable(mod.run_tests):
                    self.output(1, "%s module: running tests" % module)
                    try:
                        mod.run_tests(verbosity_level)
                    except Exception, e:
                        log_error(module, "Exception running tests", ''.join(traceback.format_exception(*sys.exc_info())[1:]))
                        continue

        # Unless we're using SQLite, remove the test database to clean up after
        # ourselves. Connect to the previous database (not the test database)
        # to do so, because it's not allowed to delete a database while being
        # connected to it.
        if settings.DATABASE_ENGINE != "sqlite3":
            db.close()
            settings.DATABASE_NAME = old_database_name
            cursor = db.cursor()
            self.output(1, "Deleting test database")
            try:
                db.connection.autocommit(1)
            except AttributeError:
                pass
            else:
                time.sleep(1) # To avoid "database is being accessed by other users" errors.
            cursor.execute("DROP DATABASE %s" % TEST_DATABASE_NAME)

        # Display output.
        if error_list:
            for d in error_list:
                print