Code coverage is a term used in software testing to describe how much program source code is covered by a testing plan. -TechnoPedia
ModuleTests comes preconfigured to handle code coverage in addition to the unit tests. You will need to have a code coverage driver installed to use this feature, such as Xdebug.
ModuleTests assumes your source code is in src/; if your code is somewhere else then you will need to modify the following line in your PHPUnit XML file:
<directory suffix=".php">./src</directory>
ModuleTests includes a ready-to-use PHPUnit template in phpunit.xml.dist. Common practice is to create a local copy of this file as phpunit.xml and add any sensitive or environment info (like database connections). Prevent phpunit.xml from being tracked in your repo by adding it to .gitignore.
PHPUnit will always use phpunit.xml before phpunit.xml.dist, if it is found.
In addition to the code source mentioned above, PHPUnit can be configured to exclude files that are not relevant to testing or would otherwise cause the coverage calculations to fail. ModuleTests starts with a few files common to CodeIgniter 4 but you may need to add your own:
<exclude>
<directory suffix=".php">./src/Views</directory>
<file>./src/Config/Routes.php</file>
</exclude>
Output is available in a variety of formats (see the Logging Section
of the PHPUnit Guide). You can adjust the default location and format of the reports by
modifying the <logging> tag:
<logging>
<log type="coverage-html" target="build/logs/html"/>
<log type="coverage-clover" target="build/logs/clover.xml"/>
<log type="coverage-php" target="build/logs/coverage.serialized"/>
<log type="coverage-text" target="php://stdout" showUncoveredFiles="false"/>
<log type="testdox-html" target="build/logs/testdox.html"/>
<log type="testdox-text" target="build/logs/testdox.txt"/>
<log type="junit" target="build/logs/logfile.xml"/>
</logging>
For more information on using the PHPUnit XML file generally see the Configuration Section of the guide.