Missing tests in implicit?

[Eve Charbonneau]

I wanted to make sure I didn't break OCP's in implicit dynamics, but did not find a test where the values are tested.
If there are some, please close this issue :)

[Pierre Puchaud]

I found two :

• test_track_marker_2D_pendulum
• test_muscle_driven_ocp_implicit

Close the issue if it's enough for you to push some changes.

[Eve Charbonneau]

I found these after, but I am still bot sure if all the cases are covered.