Steps_Unit_test_magento2.txt

To run Unit Tests for a particualar module Magento2 

1) copy \Magento2_root\dev\tests\unit\phpunit.xml.dist to \Magento2_root\dev\tests\unit\phpunit.xml

2) Edit phpinit.xml for the module to be tested as below:  (Create folder Unit, under Test as shown)
   <testsuite name="Magento Unit Tests">
        <directory suffix="Test.php">../../../app/code/Vendor/Module/Test/Unit</directory>  
		
3) comment out the other directory tags inside the <testsuite> tag.

4) Inside 'Unit' folder, copy the Block or Model or Helper to be tested & make changes as :

  namespace Vendor\Module\Test\Unit\Block\...
  class <className>Test extends \PHPUnit_Framework_TestCase     //suffix should be Test as given in phpinit.xml
  {
     public function test<functionName>()
	 {
		...
	 }
	
  }
  
5) To run UnitTest
Under Magento2 root run:
vendor/bin/phpunit -c dev/tests/unit/phpunit.xml app/code/Vendor/Module/Test/Unit/

or  

php vendor/phpunit/phpunit/phpunit -c dev/tests/unit/phpunit.xml app/code/Vendor/Module/Test/Unit/

To run all modules Unit tests:  php bin/magento dev:tests:run unit