To Run Test Case Follow Below Steps:

1. Verify phpunit installed.
2. If not install it by follwing guideline mentioned in this site. https://phpunit.readthedocs.io/en/9.2/installation.html#composer
   a. "composer require --dev phpunit/phpunit ^9.5"
   b. If already installed then update. If getting error then uninstall then reinstall. "composer remove phpunit/phpunit" OR "composer remove --dev phpunit/phpunit"
3. While updating composer if your php version displayed wrong then just run.
   a. "composer config platform.php <CURRENT PHP VERSION>"
4. On  your root direcotory open terminal (Git Bash, CMD)
5. Run ./vendor/bin/phpunit --bootstrap ./<DIR>/bootstrap.php ./<DIR>/<FILE WITH EXTENSION>
   a. bootstrap.php having all configuration related constants and other settings. It will load this file before run test.
   b. ./vendor/bin/phpunit --filter <ANY FUNCTION NAME> --bootstrap ./<DIR>/bootstrap.php ./<DIR>/<FILE WITH EXTENSION> this is used to run function individually.

Development Notes: 

=> Use @test [In doc comments] instead of test prefix in function name.
   Example :
   /**
     * @test
     *
     * @dataProvider feedGetRates     
     */
    public function getRates($toCurrencies){}
    
=> For dataProvider user feed prefix in function name.
   Example :
   /**
     * feedGetRates
     *
     * @return array
     */
    public function feedGetRates(){}

=> $this->expectedReturnType(<TYPE>) used if calling function return type defined.
   Example : $this->expectedReturnType(static::TYPE_ARRAY);


Execute Unit test cases :

1) ./vendor/bin/phpunit --bootstrap ./testcases/bootstrap.php ./testcases/plugins/FixerCurrencyConverterTest.php
2) ./vendor/bin/phpunit --bootstrap ./testcases/bootstrap.php ./testcases/models/ShopTest.php
3) ./vendor/bin/phpunit --bootstrap ./testcases/bootstrap.php ./testcases/models/. [Will execute all test files inside models]