diff --git a/tests/test_automatic_differentiation.py b/tests/test_automatic_differentiation.py
index 84a50d6c5..4cac7cb34 100644
--- a/tests/test_automatic_differentiation.py
+++ b/tests/test_automatic_differentiation.py
@@ -297,7 +297,7 @@ def test_ad_integration(
 
     _, subkey = jax.random.split(prng_key, num=2)
     data, references = get_random_data_and_references(
-        model=model, velocity_representation=VelRepr.Inertial, key=subkey
+        model=model, velocity_representation=VelRepr.Mixed, key=subkey
     )
 
     # State in VelRepr.Inertial representation.
@@ -308,7 +308,7 @@ def test_ad_integration(
     ṡ = data.joint_velocities
 
     # Inputs.
-    W_f_L = references.link_forces(model=model)
+    LW_f_L = references.link_forces(model=model, data=data)
     τ = references.joint_force_references(model=model)
 
     # ====
@@ -323,7 +323,7 @@ def step(
         W_v_WB: jtp.Vector,
         ṡ: jtp.Vector,
         τ: jtp.Vector,
-        W_f_L: jtp.Matrix,
+        LW_f_L: jtp.Matrix,
     ) -> tuple[jax.Array, jax.Array, jax.Array, jax.Array, jax.Array]:
 
         # When JAX tests against finite differences, the injected ε will make the
@@ -344,7 +344,7 @@ def step(
             model=model,
             data=data_x0,
             joint_force_references=τ,
-            link_forces=W_f_L,
+            link_forces_mixed=LW_f_L,
         )
 
         xf_W_p_B = data_xf.base_position
@@ -360,7 +360,7 @@ def step(
     # current implementation of `optax` optimizers in the relaxed rigid contact model.
     check_grads(
         f=step,
-        args=(W_p_B, W_Q_B, s, W_v_WB, ṡ, τ, W_f_L),
+        args=(W_p_B, W_Q_B, s, W_v_WB, ṡ, τ, LW_f_L),
         order=AD_ORDER,
         modes=["fwd"],
         eps=ε,
diff --git a/tests/test_simulations.py b/tests/test_simulations.py
index 86e3696e3..93f19ccff 100644
--- a/tests/test_simulations.py
+++ b/tests/test_simulations.py
@@ -69,13 +69,14 @@ def test_box_with_external_forces(
     data = data0.copy()
 
     # ... and step the simulation.
-    for _ in T_ns:
+    with references.switch_velocity_representation(VelRepr.Mixed):
+        for _ in T_ns:
 
-        data = js.model.step(
-            model=model,
-            data=data,
-            link_forces=references.link_forces(model=model, data=data),
-        )
+            data = js.model.step(
+                model=model,
+                data=data,
+                link_forces_mixed=references.link_forces(model=model, data=data),
+            )
 
     # Check that the box didn't move.
     assert data.base_position == pytest.approx(data0.base_position)
@@ -143,13 +144,14 @@ def test_box_with_zero_gravity(
     data = data0.copy()
 
     # ... and step the simulation.
-    for _ in T:
+    with references.switch_velocity_representation(jaxsim.VelRepr.Mixed):
+        for _ in T:
 
-        data = js.model.step(
-            model=model,
-            data=data,
-            link_forces=references.link_forces(model=model, data=data),
-        )
+            data = js.model.step(
+                model=model,
+                data=data,
+                link_forces_mixed=references.link_forces(model=model, data=data),
+            )
 
     # Check that the box moved as expected.
     assert data.base_position == pytest.approx(