style: canonicalize black formatting on test files

tests/physics/test_multi_branch.py

@@ -637,9 +637,9 @@ class TestMultiBranchEdgeCases:
         W, _ = spectrum.get_energy_grid(config)
 
         values = spectrum(W)
-        assert np.all(np.isfinite(values)), (
-            "High-Z multi-branch must not produce NaN/inf"
-        )
+        assert np.all(
+            np.isfinite(values)
+        ), "High-Z multi-branch must not produce NaN/inf"
 
     def test_no_branches_defaults_to_single(self):
         """No branches list should default to single-branch mode."""
@@ -705,9 +705,9 @@ class TestMultiBranchEdgeCases:
             contrib = universal_product * branch.intensity * bs[i]
 
             # Branch contribution should not exceed total
-            assert np.all(contrib <= total + 1e-10), (
-                f"Branch {i} contribution exceeds total at some points"
-            )
+            assert np.all(
+                contrib <= total + 1e-10
+            ), f"Branch {i} contribution exceeds total at some points"
 
             # Branch contribution should be non-negative
             assert np.all(contrib >= 0), f"Branch {i} contribution has negative values"
@@ -759,6 +759,6 @@ class TestMultiBranchEdgeCases:
             assert integral > 0, f"Branch {i} has zero integral"
 
         # Sum of branch integrals should equal total
-        assert np.isclose(sum(integrals), total_integral, rtol=1e-6), (
-            "Sum of branch integrals should equal total integral"
-        )
+        assert np.isclose(
+            sum(integrals), total_integral, rtol=1e-6
+        ), "Sum of branch integrals should equal total integral"