Test coverage analysis and comparison using PHP and PHPUnit

With the continuous advancement of software development, more and more developers are aware of the importance of testing. Testing can help developers find errors in the code and improve the quality and maintainability of the code. However, the number of tests is usually very large, and manual testing is also very time-consuming and laborious. Therefore, the use of automated testing tools has become particularly important. One of the tools is PHPUnit. PHPUnit is a popular PHP testing framework that can quickly and efficiently execute test cases and generate visual test reports. This article will introduce how to use PHPUnit to implement test coverage analysis and comparison.

1. What is test coverage?

Test coverage refers to the coverage of the program code execution path by the test case, that is, the proportion of the code that is executed when the use case is executed. It is an important indicator of test quality. In actual development, test coverage is generally divided into statement coverage, branch coverage, condition coverage and path coverage. Statement coverage is the most basic one and the easiest to implement.

2. Use PHPUnit to implement test coverage analysis

PHPUnit provides a very convenient test coverage analysis tool PHPUnit_Coverage, which can be used to collect code coverage information and generate reports. PHPUnit_Coverage supports the xdebug extension by default, so before using PHPUnit_Coverage to analyze test coverage, you need to ensure that the xdebug extension has been installed. If it is not installed, you need to install xdebug through PECL first. After installing xdebug, you need to add the following configuration to the php.ini file:

[xdebug]
zend_extension="/usr/local/opt/php@7.3/pecl/20180731/xdebug.so"
xdebug.coverage_enable=On
xdebug.profiler_enable_trigger=On
xdebug.profiler_output_name="%R.%U"
xdebug.profiler_output_dir="/tmp"

The above configuration is to enable xdebug's coverage analysis and code performance analysis functions, and to enable automatic output of analysis results.

Next, we need to add the code coverage generator in phpunit.xml and specify the path to generate the coverage.xml file:

    
        ./src
    
    
        
        
        
        
    
    
        
    

When running the PHPUnit test case, add -- Coverage-html=build/coverage command line parameters can automatically generate code coverage reports.

3. Use PHPUnit to achieve test coverage comparison

Test coverage comparison refers to comparing the test coverage reports of two versions to understand the changes in test cases. PHPUnit provides a test coverage comparison tool SebastianBergmannDiff to implement this function. Using SebastianBergmannDiff to compare test coverage is simple, just follow these steps:

1. Install the SebastianBergmannDiff package

composer require sebastian/diff

2. Write the comparison method

public function testCoverage()
{
    $oldCoverage = new PHP_CodeCoverage();
    $oldCoverage->append($this->getCoverageData('old_coverage.xml'));

    $newCoverage = new PHP_CodeCoverage();
    $newCoverage->append($this->getCoverageData('new_coverage.xml'));

    $diff = $this->compareCoverages($oldCoverage, $newCoverage);

    $this->assertEmpty($diff, 'Coverage has not changed.');
}

private function compareCoverages(PHP_CodeCoverage $oldCoverage, PHP_CodeCoverage $newCoverage): string
{
    $oldReport = new CodeCoverageReportHtmlFacade;
    $oldReport->process($oldCoverage, '/tmp/old-coverage');

    $newReport = new CodeCoverageReportHtmlFacade;
    $newReport->process($newCoverage, '/tmp/new-coverage');

    $oldXml = $this->getXml('/tmp/old-coverage/index.html');
    $newXml = $this->getXml('/tmp/new-coverage/index.html');

    $differ = new SebastianBergmannDiffDiffer;
    return $differ->diff($oldXml, $newXml);
}

private function getXml(string $file): SimpleXMLElement
{
    return simplexml_load_string(file_get_contents($file), 'SimpleXMLElement', LIBXML_NOCDATA);
}

private function getCoverageData(string $filename): array
{
    $result = [];

    $xml = file_get_contents($filename);
    $coverage = new PHP_CodeCoverage();
    $coverage->setDataToBeUnserialized($xml);

    $filter = $coverage->getFilter();
    $filter->addDirectoryToWhitelist('/app');
    $filter->addDirectoryToWhitelist('/tests');

    foreach ($coverage->getData() as $filename => $data) {
        $result[$filename] = [
            'executed' => $data['executedLines'],
            'unexecuted' => $data['executableLines'] - $data['executedLines']
        ];
    }

    return $result;
}

In the code, we First load the test coverage reports of the old version and the new version and compare them through the compareCoverages method. If the comparison result is empty, it means that the test coverage has not changed.

4. Summary

This article introduces how to use PHPUnit to implement test coverage analysis and comparison. Test coverage is one of the important indicators of software testing, which can help developers evaluate the coverage of test cases, thereby improving the quality and maintainability of the code. PHPUnit is a popular PHP testing framework that provides a wealth of testing tools and report generators, and can perfectly support test coverage analysis and comparison.

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