fix: check for angular momentum in form factor (#230)

* ci: compute full test coverage in tox job

src/ampform/helicity/__init__.py

@@ -746,13 +746,17 @@ def _generate_kinematic_variable_set(
         get_invariant_mass_label(transition.topology, decay.children[1].id),
         real=True,
     )
+    angular_momentum: Optional[int] = decay.interaction.l_magnitude
+    if angular_momentum is None:
+        if decay.parent.particle.spin.is_integer():
+            angular_momentum = int(decay.parent.particle.spin)
     return TwoBodyKinematicVariableSet(
         incoming_state_mass=inv_mass,
         outgoing_state_mass1=child1_mass,
         outgoing_state_mass2=child2_mass,
         helicity_theta=theta,
         helicity_phi=phi,
-        angular_momentum=decay.extract_angular_momentum(),
+        angular_momentum=angular_momentum,
     )
 
 

src/ampform/helicity/decay.py

@@ -80,18 +80,6 @@ def from_transition(
             interaction=transition.interactions[node_id],
         )
 
-    def extract_angular_momentum(self) -> int:
-        angular_momentum = self.interaction.l_magnitude
-        if angular_momentum is not None:
-            return angular_momentum
-        spin_magnitude = self.parent.particle.spin
-        if spin_magnitude.is_integer():
-            return int(spin_magnitude)
-        raise ValueError(
-            f"Spin magnitude ({spin_magnitude}) of single particle state"
-            " cannot be used as the angular momentum as it is not integral!"
-        )
-
 
 def get_helicity_info(
     transition: StateTransition, node_id: int

tox.ini

@@ -22,7 +22,7 @@ description =
 allowlist_externals =
     pytest
 commands =
-    pytest {posargs:tests} \
+    pytest {posargs:src tests} \
         --cov-fail-under=75 \
         --cov-report=html \
         --cov-report=xml \