For CiviCRM 4.3 and 4.2:

Install extension
 
You can get Braintree Payment Processor Extension from here : https://github.com/vivekarora/braintree


Tasks need to be done after installing the extension.

1. signup to https://www.braintreepayments.com/get-started 
2. Go to System Settings -> Payment Processors
3. Select Braintree from Payment processor type dropdown
4. Fill the Merchant Id,Public Key and Private Key which will you get when you login to https://sandbox.braintreegateway.com

Tasks needs to be done to run the test cases.

1. Go to the tests folder of the extention.
2. Copy All files inside the com.paymentprocessor.braintree/tests/phpunit/WebTest/Cotribute and paste it in civicrm(Your Civicrm module directory)/tests/phpunit/WebTest/Cotribute 
3. Copy All files inside the com.paymentprocessor.braintree/tests/phpunit/WebTest/Event and paste it in civicrm(Your Civicrm module directory)/tests/phpunit/WebTest/Event  
4. Copy All files inside the com.paymentprocessor.braintree/tests/phpunit/WebTest/Member and paste it in civicrm(Your Civicrm module directory)/tests/phpunit/WebTest/Member   
5. cd path/to/civicrm/packages/SeleniumRC 
6. sh selenium.sh

Now you are all set to run the web tests.

To run 

Online Contribution tests

       scripts/phpunit -uUSERNAME -pPASSWORD -hHOST -bTESTDBNAME WebTest_Contribute_OnlineContributionBraintreeTest

Offline Contribution tests

        scripts/phpunit -uUSERNAME -pPASSWORD -hHOST -bTESTDBNAME WebTest_Contribute_OfflineContributionBraintreeTest


 Event creation and Online registration tests

        scripts/phpunit -uUSERNAME -pPASSWORD -hHOST -bTESTDBNAME WebTest_Event_AddEventBraintreeTest


 Event creation and Ofline  add participants tests

       	 scripts/phpunit -uUSERNAME -pPASSWORD -hHOST -bTESTDBNAME WebTest_Event_AddParticipationBraintreeTest


 Online membership signup

         scripts/phpunit -uUSERNAME -pPASSWORD -hHOST -bTESTDBNAME  WebTest_Member_OnlineMembershipBraintreeCreateTest

 Offline membership payment and autorenew
 
          scripts/phpunit -uUSERNAME -pPASSWORD -hHOST -bTESTDBNAME WebTest_Member_OfflineAutoRenewBraintreeMembershipTest