python - 使用 PostgreSQL 在 SQLAlchemy 测试中创建数据库

Question

我正在构建一个 Pyramid 网络应用程序，该应用程序构建在 SQLAlchemy 之上，并且完全依赖 PostgreSQL 作为其数据库后端。

有什么方法可以使单元测试结构如此

• 数据库在每次测试运行时构建一次 - 不是在每次测试时都构建 setUp() 因为这对于复杂的应用程序来说太慢了

• (重新)创建数据库表，就像它们在生产中创建的一样(例如，从 Alembic 运行迁移)。任何不干净的数据库都会在测试运行开始时被销毁。

• 如果标准库 unittest 框架之外的特定功能使编写测试用例变得更容易，则可以选择自定义测试运行程序 la py.test。

Answer 1

Nose测试运行器支持 setup_package() 和 teardown_package() 方法。以下是文档的摘录:

Test Packages

nose allows tests to be grouped into test packages. This allows package-level setup; for instance, if you need to create a test database or other data fixture for your tests, you may create it in package setup and remove it in package teardown once per test run, rather than having to create and tear it down once per test module or test case.

To create package-level setup and teardown methods, define setup and/or teardown functions in the init.py of a test package. Setup methods may be named setup, setup_package, setUp, or setUpPackage; teardown may be named teardown, teardown_package, tearDown or tearDownPackage. Execution of tests in a test package begins as soon as the first test module is loaded from the test package.

在我的应用程序中，我有 setup_package()，它大致如下所示:

def _create_database():

    template_engine = sa.create_engine("postgres://postgres@/postgres", echo=False)

    conn = template_engine.connect()
    conn = conn.execution_options(autocommit=False)
    conn.execute("ROLLBACK")
    try:
        conn.execute("DROP DATABASE %s" % DB_NAME)
    except sa.exc.ProgrammingError as e:
        # Could not drop the database, probably does not exist
        conn.execute("ROLLBACK")
    except sa.exc.OperationalError as e:
        # Could not drop database because it's being accessed by other users (psql prompt open?)
        conn.execute("ROLLBACK")

    conn.execute("CREATE DATABASE %s" % DB_NAME)
    conn.close()

    template_engine.dispose()


def setup_package():
    _create_database()

    engine = sa.create_engine("postgres://postgres@/%s" % DB_NAME, echo=False)

    session = sa.orm.scoped_session(sa.orm.sessionmaker())
    session.configure(bind=engine)
    Base.metadata.bind = engine
    Base.metadata.create_all()


def teardown_package():
    # no need to do anything as the old database is dropped at the start of every run

此外，所有测试用例类都是基类的子类，重要的是，基类定义了一个通用的tearDown 方法:

class BaseTest(unittest.TestCase):

    def setUp(self):
        # This makes things nicer if the previous test fails
        # - without this all subsequent tests fail
        self.tearDown()

        self.config = testing.setUp()

    def tearDown(self):
        testing.tearDown()
        session.expunge_all()
        session.rollback()

子类通常会覆盖基础 setUp，但通常不需要覆盖 tearDown - 通过回滚事务，它确保下一次测试将在完全干净的数据库上开始.