我看到很多问题都在问“如何”用一种特定的语言进行单元测试,但没有人问“什么”、“为什么”和“什么时候”。
是什么? 它对我有什么用? 我为什么要用它? 什么时候用(什么时候不用)? 有哪些常见的陷阱和误解
我看到很多问题都在问“如何”用一种特定的语言进行单元测试,但没有人问“什么”、“为什么”和“什么时候”。
是什么? 它对我有什么用? 我为什么要用它? 什么时候用(什么时候不用)? 有哪些常见的陷阱和误解
当前回答
单元测试是在不需要该代码单元所依赖的基础设施的情况下对代码单元(例如单个函数)进行测试。即在隔离环境中进行测试。
例如,如果您正在测试的函数连接到数据库并执行更新,那么在单元测试中您可能不想执行该更新。如果这是一个积分测试,你会这样做,但在这个例子中,它不是。
因此,单元测试将测试您正在测试的“函数”中所包含的功能,而不会产生数据库更新的副作用。
假设函数从数据库中检索了一些数字,然后执行标准偏差计算。你想测试什么?标准偏差计算正确,还是数据从数据库返回?
在单元测试中,您只想测试标准偏差的计算是否正确。在集成测试中,您希望测试标准偏差计算和数据库检索。
其他回答
这回答了为什么您应该进行单元测试。
下面的三个视频涵盖了javascript中的单元测试,但一般原则适用于大多数语言。
单元测试:现在的几分钟将节省几小时后- Eric Mann - https://www.youtube.com/watch?v=_UmmaPe8Bzc
JS单元测试(非常好)- https://www.youtube.com/watch?v=-IYqgx8JxlU
编写可测试的JavaScript - https://www.youtube.com/watch?v=OzjogCFO4Zo
Now I'm just learning about the subject so I may not be 100% correct and there's more to it than what I'm describing here but my basic understanding of unit testing is that you write some test code (which is kept separate from your main code) that calls a function in your main code with input (arguments) that the function requires and the code then checks if it gets back a valid return value. If it does get back a valid value the unit testing framework that you're using to run the tests shows a green light (all good) if the value is invalid you get a red light and you then can fix the problem straight away before you release the new code to production, without testing you may actually not have caught the error.
So you write tests for you current code and create the code so that it passes the test. Months later you or someone else need to modify the function in your main code, because earlier you had already written test code for that function you now run again and the test may fail because the coder introduced a logic error in the function or return something completely different than what that function is supposed to return. Again without the test in place that error might be hard to track down as it can possibly affect other code as well and will go unnoticed.
Also the fact that you have a computer program that runs through your code and tests it instead of you manually doing it in the browser page by page saves time (unit testing for javascript). Let's say that you modify a function that is used by some script on a web page and it works all well and good for its new intended purpose. But, let's also say for arguments sake that there is another function you have somewhere else in your code that depends on that newly modified function for it to operate properly. This dependent function may now stop working because of the changes that you've made to the first function, however without tests in place that are run automatically by your computer you will not notice that there's a problem with that function until it is actually executed and you'll have to manually navigate to a web page that includes the script which executes the dependent function, only then you notice that there's a bug because of the change that you made to the first function.
重申一下,在开发应用程序时运行测试将在编写代码时发现这类问题。如果没有适当的测试,你必须手动检查整个应用程序,即使这样也很难发现错误,你天真地将其发送到生产环境中,一段时间后,好心的用户会给你发送错误报告(这不会像你在测试框架中的错误消息那样好)。
It's quite confusing when you first hear of the subject and you think to yourself, am I not already testing my code? And the code that you've written is working like it is supposed to already, "why do I need another framework?"... Yes you are already testing your code but a computer is better at doing it. You just have to write good enough tests for a function/unit of code once and the rest is taken care of for you by the mighty cpu instead of you having to manually check that all of your code is still working when you make a change to your code.
此外,如果你不想进行单元测试,你也不必进行单元测试,但随着你的项目/代码库开始变得越来越大,引入错误的可能性也在增加,这是值得的。
我在FoxForward 2007参加了一个关于单元测试的演讲,被告知永远不要对任何与数据相关的东西进行单元测试。毕竟,如果您在实时数据上进行测试,结果是不可预测的,如果您不在实时数据上进行测试,那么实际上并不是在测试您所编写的代码。不幸的是,这是我最近编写的大部分代码。: -)
最近,当我编写一个保存和恢复设置的例程时,我确实尝试了TDD。首先,我验证了是否可以创建存储对象。然后,它有我需要调用的方法。然后,我可以称之为。然后,我可以给它传递参数。然后,我可以给它传递特定的参数。依此类推,直到我最终验证它将保存指定的设置,允许我更改它,然后为几种不同的语法恢复它。
我没看完,因为我现在需要例行公事,但这是一个很好的练习。
单元测试是在不需要该代码单元所依赖的基础设施的情况下对代码单元(例如单个函数)进行测试。即在隔离环境中进行测试。
例如,如果您正在测试的函数连接到数据库并执行更新,那么在单元测试中您可能不想执行该更新。如果这是一个积分测试,你会这样做,但在这个例子中,它不是。
因此,单元测试将测试您正在测试的“函数”中所包含的功能,而不会产生数据库更新的副作用。
假设函数从数据库中检索了一些数字,然后执行标准偏差计算。你想测试什么?标准偏差计算正确,还是数据从数据库返回?
在单元测试中,您只想测试标准偏差的计算是否正确。在集成测试中,您希望测试标准偏差计算和数据库检索。
使用Testivus。你需要知道的都在那里:)
测试驱动开发在某种程度上取代了单元测试这个术语。作为一个老手,我会提到它的更一般的定义。
单元测试还意味着测试一个较大系统中的单个组件。这个组件可以是dll、exe、类库等。它甚至可以是多系统应用程序中的单个系统。因此,单元测试最终是对一个更大系统的单个部分进行测试。
然后,您可以通过测试所有组件如何一起工作来进行集成测试或系统测试。