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An important practice to get all of this to work is

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continuous integration, which means integrating and

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testing every few hours, or a

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day at most, because we don't want problems to pile up and

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to be discovered too late when there are too many of them

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to fix. So what goes on here is a cycle. And the

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cycle starts with the developer's programming, as soon as the developers are

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done modifying the code and they have a stable version they will

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run the local tests. If the local tests fail, the developers will

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go back to programming to fix their code and possibly add

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new code as needed, and this cycle, mini cycle will continue

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until all the local tests pass. At that point the developers

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can integrate their code with the code of other developers. And they

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can run test for the integrated system, and when they run

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this test again there are two possibilities. The test might fail, and

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if the test fails you broke it, and therefore you'll have

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to fix it. So developers will have to go back and modify

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the system and again going through the cycle of running the local

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tests, integrating, and running the systems

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tests. Conversely, if all the systems

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tests pass, then at that point the code is good to go

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and it is integrated into the system. And it will be the problem

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of some other developers if something breaks because at the time you

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integrated your code, the code was compiling, running and passing the tests

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successfully. So again, if we do this every few hours or every

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day, we can find problems very early, and we can avoid the situations

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in which we have many different changes coming from

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many different developers in a integration nightmare as a result.