In each D3 project, tests around ‘aligning’ elements to the x and y axis often fail without a proper explanation. Even when the examples from the lessons are followed exactly, the tests seem highly inconsistent. Please give us more information on what these tests do and how to pass them.
D3 is in essence a library for visualizations. If the result is visually correct, then the solution should be accepted. Whether or not I align my axis in the top-secret way your test requires should matter very little. The axes are such a small portion of what D3 has to offer, yet 99% of the work and frustration I have put in to these projects went to these very obscure ‘align’ tests.