FutureTest.cls

public with sharing class FutureTest {
	
	@future
	public static void createAccountFuture() {
		Account a = new Account(Name='Test Account');
		//User with the standard Read Only profile should not be able to insert an account
		insert a;
	}

	///////////////TESTS////////////////////

	static testMethod void testFutureCall() {
		Profile p = [SELECT id FROM Profile WHERE Name ='Read Only' LIMIT 1];
		user u = new User(alias = 'person', email='guest@testpkg.com',
                     emailencodingkey='UTF-8', firstname='Test', lastname='Person', languagelocalekey='en_US',
                     localesidkey='en_US', profileid = p.id,
                     timezonesidkey='America/Los_Angeles', username='guest@testpkg.com');

		insert u;

		Test.startTest();
		system.runAs(u) {
			FutureTest.createAccountFuture();
		}
		Test.stopTest();

		Account[] createdAcounts = [SELECT id FROM Account WHERE Name = 'Test Account'];
		system.assert(createdAcounts.size() == 1);
	}

}