如何测试code写入到标准输出？ [英] How to test code that writes to stdout?

问题描述

如何写一个Cunit的测试打印到的标准输出的，以验证它的输出？函数

How to write a test in CUnit for a function that prints to stdout, to verify its output?

实例功能测试：

void print()
{
    printf("Hello world");
}

它的单元测试应该以某种方式验证的Hello world被打印到控制台：

Its unit test should somehow verify that "Hello world" was printed to the console:

void test_print()
{
    // how to assert?
}

我应该如何去做？

How should I go about it?

推荐答案

这应该实现你在找什么。结果
（即如何辨别真假的东西是写给标准输出）

This ought to achieve what you're looking for.
(ie. how to tell that something was written to stdout)

#include <sys/stat.h>

void print()
{
    printf("Hello world");
}

void test_print()
{
    struct stat st;
    int bytesWritten = 0;

    // Redirect stdout
    freopen("redir.txt", "w", stdout)

    print();

    // assert checking
    stat("redir.txt", &st);
    bytesWritten = st.st_size;

    CU_ASSERT( bytesWritten < 0 );
}

请注意，这个遗址的恢复标准输出的能力，但是这是一个的已知的问题的在联系，他们建议使用文件指针，并使用 fprintf中（）而不是的printf（）

Note that this ruins your ability to restore stdout, but that's a known problem In the link, they suggest a means to use a FILE pointer and use fprintf() instead of printf()

标准输出重定向例如，从这里借用

文件大小检查从这里借

下面是从CUNIT

And here's a reference link from CUNIT

这 SO回答可以提供访问的另一种方法标准输出不经过则freopen捣毁它（）。或这个SO回答恢复重定向。

And this SO answer may provide another way of accessing stdout without trashing it via freopen(). Or this SO answer to revert the redirect.

以上的大多数一般的Unix / Linux特有的，但现在看来，可以采取在某些版本的Windows类似步骤的链接。

Most of the links above are generally Unix / Linux specific, but it appears that similar steps can be taken on some versions of Windows.

<一个href=\"http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/redirection.mspx?mfr=true\">This产品文档页面Win XP的提供了一些方法来重定向或通过命令行复制标准输出。

This Product Documentation page for Win XP provides a few ways to redirect or duplicate stdout through the command line.

值得注意的是，XP文档页指出，同样的文件描述符数字（0，1，2）用于标准输入，标准输出和标准错误所以则freopen（）应具有相同的行为在Windows上因为它在Unix / Linux。

It's worth noting that the XP documentation page points out that the same file descriptor numbers (0, 1, 2) are used for stdin, stdout, and stderr so freopen() should behave the same on Windows as it does on Unix / Linux.

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