TestCase 和 TransactionTestCase 是 TestCase 用包装测试atomic（）始终阻止。从文档：

The main difference between TestCase and TransactionTestCase is that TestCase wraps the tests with atomic() blocks ALL THE TIME. From the documentation:

将测试包装在两个嵌套的atomic（）块中：一个用于整个类，一个用于每个测试

Wraps the tests within two nested atomic() blocks: one for the whole class and one for each test

现在假设您有一个方法，如果该方法未包装在 atomic（）块中，则会引发错误。您正在尝试为此进行测试：

Now imagine that you have a method that should raise an error if it is not wrapped inside atomic() block. You are trying to write a test for that:

def test_your_method_raises_error_without_atomic_block(self):
    with self.assertRaises(SomeError):
        your_method()

此测试会意外失败！您猜对了，原因是 TestCase 始终用 atomic（）阻止测试。因此， your_method（）不会引发错误，因此该测试将失败。在这种情况下，您应该使用TransactionTestCase进行测试。

This test will unexpectedly fail! The reason is, you guessed it, TestCase wraps the tests with atomic() blocks ALL THE TIME. Thus, your_method() will not raise an error, which is why this test will fail. In this case, you should use TransactionTestCase to make your test pass.

select_for_update（）很明显：

在支持SELECT ... FOR UPDATE的后端以自动提交模式使用select_for_update（）评估查询集

Evaluating a queryset with select_for_update() in autocommit mode on backends which support SELECT ... FOR UPDATE is a TransactionManagementError error

从 TransactionTestCase文档：

使用TestCase类，您不能测试代码块是否在事务内执行，这是使用select_for_update（）时所必需的

with TestCase class, you cannot test that a block of code is executing within a transaction, as is required when using select_for_update()

如果我们查看 select_for_update（）的文档，警告：

And if we take a look at the documentation of select_for_update(), we see a warning:

尽管select_for_update（）在自动提交模式下通常会失败，因为TestCase自动将每个测试包装在事务中，因此即使在atomic（）块之外调用Test_ase中的select_for_update（）也将（可能意外地）通过而不会提高一个TransactionManagementError。要正确测试select_for_update（），应使用TransactionTestCase。

Although select_for_update() normally fails in autocommit mode, since TestCase automatically wraps each test in a transaction, calling select_for_update() in a TestCase even outside an atomic() block will (perhaps unexpectedly) pass without raising a TransactionManagementError. To properly test select_for_update() you should use TransactionTestCase.

希望它会有所帮助！