how do i get the assertions list test data wise in a test

While not exactly what you requested, the following code can be placed into a TestRunListener.afterRun event handler it shows you how to get hold of the assertion error message that Ready API displays:

import com.eviware.soapui.model.testsuite.Assertable.AssertionStatus

def logPrefix = testRunner.getTestCase().getName() + ': '

// Loop through all of the test step results.
testRunner.getResults().each(){ testStepResult ->

	log.info(logPrefix + 'Test step ' + testStepResult.getTestStep().getName() + ' result status = ' + testStepResult.getStatus().toString())

     // Loop through all of the assertions.
     testStepResult.getTestStep().getAssertionList().each() { assertion ->

		log.info(logPrefix + 'Assertion ' +  assertion.getName() +  ' returned status = ' + assertion.getStatus())

		// Check to see if current assertion has failed?
	     if(assertion.getStatus().toString().equals('FAILED')){

			// Loop through all of the failed assertions error messages
			assertion.getErrors().each() { assertionError ->
	      		log.info(logPrefix + assertionError.getErrorLevel().toString() + ' message = ' + assertionError.getMessage())
	      	}
	     }
     }
}

Hopefully this will get you started.