title: tests for data access (sql queries) functionality
body: <p>I want to know the best way of testing data access functionality. <br>
  I know that it is possible to create mocks to change data layer objects that is using to test business logic.<br>
  However is it possible to test if sql queries to database are correct.<br></p>
  
  <p>Scenario: A method must return employees which were applied for work last month.<br>
  I can return list of object and check if each employee's startDate property is correct (last month).<br>
  So if it returns 3 employees and they have correct startDate value but there are more two employee in database which aren't returned. How to write test for that case? :)</p>
  
  <p>Thanks in advance.</p>