在MiniTest中assert_predicate有什么用？

Question

我在了解MiniTest中assert_predicate的用处时遇到了问题。它与assert_equal?有何不同？何时想要使用这个断言？我已经多次遇到它，但并没有真正得到它的确切含义。

Answer 1

assert_equal检查预期值和实际值是否相等：

assert_equal "Bender", robot.name

assert_predicate调用目标对象上的named方法，如果结果是真的则传递：

assert_predicate robot, :bender?

您可以轻松地将此测试编写为：

assert robot.bender?

但assert_predicate在某些情况下可能更具表现力，在检查多个谓词条件时可能会更好一点：

roles = %i(admin? publisher? operator?)
roles.each {|role| assert_predicate user, role }

Answer 2

The documentation for the method itself may answer your question:

For testing with predicates. Eg:

assert_predicate str, :empty?

This is really meant for specs and is front-ended by assert_operator:

str.must_be :empty?

That suggests that the reason is to support .must_be calls rather than providing any specific benefit over assert_equal or assert.