A Concordion developer uses the Concordion tool, a behavior-driven development (BDD) framework, to create automated acceptance tests. The developer writes specifications in business language, which are then converted into automated tests. These tests are written as HTML or Markdown documents containing actual examples and expected outcomes. The Concordion developer integrates these tests with the application code, making it easy to verify that the software works as expected. The role requires knowledge of Java, as Concordion uses Java for its fixtures. The developer also ensures that the tests remain updated as the software evolves, ensuring continuous quality control.