如何阅读/改进 PHP 计算的 C.R.A.P 指数

我刚开始使用 PHPUnit 及其丰富多彩的代码覆盖率报告.我理解所有的数字和百分比，除了一个:C.R.A.P 指数.谁能给我一个可靠的解释，解释它的含义，如何分析它以及如何降低它?

解决方案

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I just started working with PHPUnit and its colorful code coverage reports. I understand all the numbers and percentages save one: The C.R.A.P index. Can anyone offer me a solid explanation of what it means, how to analyze it and how to lower it?

解决方案

@Toader Mihai offered a solid explanation. (+1 from me)

How to lower it:

Write less complex code OR write better tested code. (See the graph below)

Better tested Code ?

In this context this just means: A higher code coverage and usually results in writing more tests.

Less complex code ?

For example: Refactor your methods into smaller ones:

// Complex
function doSomething() {
    if($a) {
        if($b) {
        }
        if($c) {
        }
    } else {
        if($b) {
        }
        if($c) {
        }
    }
}

// 3 less complex functions
function doSomething() {
    if($a) {
        doA();
    } else {
        doNotA();
    }
}

function doA() {
    if($b) {
    }
    if($c) {
    }
}

function doNotA() {
    if($b) {
    }
    if($c) {
    }
}

(just a trivial example, you'll find more resources for that i'm sure)

Additional resources:

First off let me provide some additional resources:

Creators blog post about the crap index

just in case: Cyclomatic complexity explained. Tools like PHP_CodeSniffer and PHPMD will tell you that number in case you want to know.

And while it is for you to decide what number is "ok" one often suggested number (that is a litte high imho) is a crap index of 30 resulting in a Graph like this:

(You can get the .ods file here: https://www.dropbox.com/s/3bihb9thlp2fyg8/crap.ods?dl=1 )