PHPUnit checking method is called once

Below we are going to use PHP Unit to check if a function was called inside a method.

First setup your class that you are going to test.
This is a simple class with two functions. mainFunction calls secondFunction.

<?php

namespace AzCodez\MagentoTraining\Controller;

class TestOneMethod
{
    public function mainFunction()
    {
        $this->secondFunction();
    }

    public function secondFunction()
    {
        return 1;
    }
}

Setup your php unit test

First setup basic configuration of calling php unit dependency so we can run tests

<?php

use PHPUnit\Framework\TestCase;

class TestOneMethodCallsTest extends TestCase
{

}

Then add real class dependency and setup a variable for it

<?php

use PHPUnit\Framework\TestCase;
use AzCodez\MagentoTraining\Controller\TestOneMethod;

class TestOneMethodCallsTest extends TestCase
{
    /**
     * @var TestOneMethod
     */
    protected $testOneMethod;

}

Add a new test funtion with comments for arranging the test, asseting (checking), and calling real class to php unit tests your class

<?php

use PHPUnit\Framework\TestCase;
use AzCodez\MagentoTraining\Controller\TestOneMethod;

class TestOneMethodCallsTest extends TestCase
{
    /**
     * @var TestOneMethod
     */
    protected $testOneMethod;

    /**
     * 
     */
    public function testFirstUnitTest()
    {
        //Arrange

        //Asset

        //Act

    }
}

Add to Arrange setting up of method.
We are mocking method so we can test it here
We don't need to set method of 'mainFunction' as we want 'mainFunction' to act like normal and call our secondFunction. We don't want to do any mocking with 'mainFunction'

<?php

use PHPUnit\Framework\TestCase;
use AzCodez\MagentoTraining\Controller\TestOneMethod;

class TestOneMethodCallsTest extends TestCase
{
    /**
     * @var TestOneMethod
     */
    protected $testOneMethod;

    /**
     * 
     */
    public function testFirstUnitTest()
    {
        //Arrange
        $this->testOneMethod = $this->getMockBuilder(TestOneMethod::class)
            ->setMethods(['secondFunction'])
            ->getMock();

        //Asset

        //Act

    }
}

Add assert
Here we are testing if the 'secondFunction' is called only once

<?php

use PHPUnit\Framework\TestCase;
use AzCodez\MagentoTraining\Controller\TestOneMethod;

class TestOneMethodCallsTest extends TestCase
{
    /**
     * @var TestOneMethod
     */
    protected $testOneMethod;

    /**
     * 
     */
    public function testFirstUnitTest()
    {
        //Arrange
        $this->testOneMethod = $this->getMockBuilder(TestOneMethod::class)
            ->setMethods(['secondFunction'])
            ->getMock();

        //Asset
        $this->testOneMethod->expects($this->once())
        ->method('secondFunction');

        //Act

    }
}

Finally add act. This is where php unit test calls our real class

<?php

use PHPUnit\Framework\TestCase;
use AzCodez\MagentoTraining\Controller\TestOneMethod;

class TestOneMethodCallsTest extends TestCase
{
    /**
     * @var TestOneMethod
     */
    protected $testOneMethod;

    /**
     * 
     */
    public function testFirstUnitTest()
    {
        //Arrange
        $this->testOneMethod = $this->getMockBuilder(TestOneMethod::class)
            ->setMethods(['secondFunction'])
            ->getMock();

        //Asset
        $this->testOneMethod->expects($this->once())
        ->method('secondFunction');

        //Act
        $this->testOneMethod->mainFunction();
    }
}

Run your test (I am running a magento instance with phpUnit inside vendor/bin/phpunit folder

./vendor/bin/phpunit -c dev/tests/unit/phpunit.xml.dist app/code/AzCodez/MagentoTraining/Test/Unit

If you want to check if you are testing properly change your assert to check if secondFunction never calls like below

<?php

use PHPUnit\Framework\TestCase;
use AzCodez\MagentoTraining\Controller\TestOneMethod;

class TestOneMethodCallsTest extends TestCase
{
    /**
     * @var TestOneMethod
     */
    protected $testOneMethod;

    /**
     * 
     */
    public function testFirstUnitTest()
    {
        //Arrange
        $this->testOneMethod = $this->getMockBuilder(TestOneMethod::class)
            ->setMethods(['secondFunction'])
            ->getMock();

        //Asset
        $this->testOneMethod->expects($this->never())
        ->method('secondFunction');

        //Act
        $this->testOneMethod->mainFunction();
    }
}

You should get error like below

Hope this works for you. Let me know if you get stuck.

Happy Coding, Asrin

If this helped you consider buying me a coffee :)

References

https://phpunit.readthedocs.io/en/9.5/
https://stackoverflow.com/questions/25214407/how-to-use-phpunit-to-test-a-method-that-calls-other-methods-of-the-same-class

PHPUnit checking method is called once

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