C test coverage in C IS will teach you how to use it

Software Test Coverage: The Key to Ensuring Code Quality

In software development, testing is crucial, and it ensures that the software runs as expected. The test coverage further ensures the comprehensiveness of the test and ensures that all branches and paths of the code are tested. Many modern programming languages ​​provide libraries or tools to generate test coverage reports, but did you know that C also has a "native" tool?

Let's start with a simple C function that returns ±42:

 <code class="c">#include <stdbool.h> int return_42(bool ret_neg) { if (ret_neg) return -42; return 42; }</stdbool.h></code>

The corresponding test code is as follows:

 <code class="c">#include <assert.h> #include <stdbool.h> #include <stdio.h> int return_42(bool ret_neg); int main() { assert(return_42(false) == 42); assert(return_42(true) == -42); puts("Nice"); return 0; }</stdio.h></stdbool.h></assert.h></code>

Generate test coverage reports using GCC/G

We can use the GCC/G compiler and its related tools to generate test coverage reports. The compilation process requires the use of -fprofile-arcs and -ftest-coverage flags:

1. Compile: Use the above flags to compile the code, which will generate an executable file and .gcno file.
2. Run test: Execute the compiled and generated test program. This generates a .gcda file after execution is finished.
3. Generate report (gcov): Use the gcov tool to process .gcda and .gcno files, and generate .gcov files. gcov will provide a simple coverage summary.

To view coverage results more intuitively, we can use the lcov tool:

1. Install lcov: Install lcov tools.
2. Collect data: Use lcov -c -d . -o foobar.info to collect coverage data.
3. Generate report: Use lcov -l foobar.info to generate more detailed reports.
4. Visual report (genhtml): Use genhtml foobar.info -o bar_html to generate HTML-formatted reports for easy viewing. This will generate a folder containing the visual coverage report.

Use genhtml to generate highly customized reports, adjusting their appearance and content through various parameters.

Hope the above information will be helpful to you!

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