从现有期望中编写自定义期望的天真方法是：
expect_failure但这不适用于expect_failure，因为expect_between(0.5, 0, 1) # PASSES
expect_between(-99, 0, 1) # FAILS
expect_between(99, 0, 1) # FAILS
expect_failure(expect_between(-99, 0, 1)) # PASSES
expect_failure(expect_between(99, 0, 1)) # FAILS <--- the problem
会抓住第一个期望。
expect_failure在编写用户定义的期望时，构建期望的正确方法是什么，以便它们仍能与Group一起使用？