PHP unit testing with real coverage

If you really need to cover all your code by tests, watch out for your short if statements.

Given the following class:

<?php

class Person
{
    /**
     * @var string
     */
    private $gender;

    /**
     * @param string $gender
     */
    public function setGender(string $gender)
    {
        $this->gender = $gender;
    }

    /**
     * @return string
     */
    public function getTitle() : string
    {
        return $this->gender === 'f' ? 'Mrs.' : 'Mr.';
    }
}

And a PHP Unit test:

<?php

use PHPUnit\Framework\TestCase;

class PersonTest extends TestCase
{
    /**
     * @dataProvider gendersAndTitle
     * @param $gender
     * @param $expectedTitle
     */
    public function testTitle($gender, $expectedTitle)
    {
        $person = new Person();
        $person->setGender($gender);

        $title = $person->getTitle();
        $this->assertEquals($expectedTitle, $title);
    }

    public function gendersAndTitle() : array
    {
        return [
            ['f', 'Mrs.'],
        ];
    }
}

If you run the test with coverage, you get a 100% coverage. But the data provider has only data for the “f/Mrs.” case, so the else branch of the short if is not actually tested, though the tested code reached the line while running the test.

Update the getTitle method from Person class using the normal if statement:

public function getTitle() : string
{
    if ($this->gender === 'f') {
        return 'Mrs.';
    }

    return 'Mr.';
}

Execute the test again and you get 80% coverage.

Here’s a Dockerfile to quickly test it yourself:

FROM php:7.2-cli-alpine3.8

RUN apk add --update --no-cache make alpine-sdk autoconf && \
    pecl install xdebug && \
    docker-php-ext-enable xdebug && \
    apk del alpine-sdk autoconf && \
    wget -O phpunit https://phar.phpunit.de/phpunit-6.phar && chmod +x phpunit

WORKDIR /src

Save the Person class to Person.php file and the test to PersonTest.php.

docker build -t phpunit-coverage .
docker run --rm -ti -v $PWD:/src phpunit-coverage sh

./phpunit --bootstrap Person.php --coverage-html coverage --whitelist Person.php .

See the coverage directory (index.html) created after running the test.

Clean up when you’re done:

docker rmi phpunit-coverage

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