We can rely on informaldocumentation to specify such invariants, but the more invariants we can formalize and check, the better.
我们可以依靠非正式文件来规定这类不变量,我们标准化和检查的不变量越多,效果就越好。
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As you'll soon see, Contract4J has the added feature of enforceable usage constraints, which is a considerable advantage over the informaldocumentation that is implicit in JUnit tests.