RSpec 对 Model 的测试的最后一步是不是以 save 对象为基准的？
describe "when name is too long" do
before { @user.name = "a" * 51 }
it { should_not be_valid }
end
类似这样的测试 要验证是不是无效，RSpec 是不是会在 Test 库上做一个 save 的实际动作来验证？
irb(main):008:0> user.valid?
User Exists (2.0ms) SELECT 1 AS one FROM "users" WHERE LOWER("users"."email") = LOWER('[email protected]') LIMIT 1
=> false
irb(main):009:0> user.invalid?
User Exists (0.6ms) SELECT 1 AS one FROM "users" WHERE LOWER("users"."email") = LOWER('[email protected]') LIMIT 1
=> true