fix: use underscores in branch names for CSV headers

beta_spectrum/visualize/__init__.py

@@ -723,11 +723,11 @@ class BetaSpectrumAnalyzer:
         if csv_verbosity == "full":
             # Per-branch spectra and components with concise branch naming
             for i in range(self._n_branches):
-                data[f"branch {i + 1}"] = self._get_branch_spectrum(i)
+                data[f"branch_{i + 1}_spectrum"] = self._get_branch_spectrum(i)
                 for comp_name in ["PhaseSpace", "Radiative"]:
                     key = self._get_component_key(i, comp_name)
                     if key in components:
-                        data[f"branch {i + 1}_{comp_name}"] = components[key]
+                        data[f"branch_{i + 1}_{comp_name}"] = components[key]
 
             # Universal components (no prefix)
             for name, values in components.items():
@@ -742,14 +742,14 @@ class BetaSpectrumAnalyzer:
                 neutrino_mass_keV = self.config.neutrino_mass_MeV * 1000
                 if branch_endpoint_keV <= neutrino_mass_keV:
                     # Branch is degenerate, spectrum should be all zeros
-                    data[f"branch {i + 1}"] = np.zeros_like(branch_spectrum)
+                    data[f"branch_{i + 1}_spectrum_normalized"] = np.zeros_like(branch_spectrum)
                 else:
                     # Branch is valid, normalize as usual
                     sum_spectrum = np.sum(branch_spectrum)
                     if sum_spectrum > 0:
-                        data[f"branch {i + 1}"] = branch_spectrum / sum_spectrum
+                        data[f"branch_{i + 1}_spectrum_normalized"] = branch_spectrum / sum_spectrum
                     else:
-                        data[f"branch {i + 1}"] = branch_spectrum
+                        data[f"branch_{i + 1}_spectrum_normalized"] = branch_spectrum
 
         df = pd.DataFrame(data)
         df.to_csv(filename, index=False, float_format="%.4e")

tests/physics/test_multi_branch.py

@@ -467,8 +467,8 @@ class TestMultiBranchCSVExport:
         assert "total_spectrum" in df.columns
 
         # Should have per-branch spectrum columns (intensity/endpoint/transition are in the header)
-        assert "branch 1" in df.columns
+        assert "branch_1_spectrum" in df.columns
-        assert "branch 2" in df.columns
+        assert "branch_2_spectrum" in df.columns
 
         # Should NOT have repeated per-branch metadata columns
         assert "branch_1_intensity" not in df.columns
@@ -503,6 +503,7 @@ class TestMultiBranchCSVExport:
         df = pd.read_csv(csv_path, comment="#")
 
         assert "total_spectrum" in df.columns
+        assert "branch_1_spectrum" in df.columns
         assert "Fermi" in df.columns
 
 
@@ -659,9 +660,9 @@ class TestMultiBranchEdgeCases:
         W, _ = spectrum.get_energy_grid(config)
 
         values = spectrum(W)
-        assert np.all(
+        assert np.all(np.isfinite(values)), (
-            np.isfinite(values)
+            "High-Z multi-branch must not produce NaN/inf"
-        ), "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."""
@@ -726,9 +727,9 @@ class TestMultiBranchEdgeCases:
             contrib = universal_product * branch.intensity * bs[i]
 
             # Branch contribution should not exceed total
-            assert np.all(
+            assert np.all(contrib <= total + 1e-10), (
-                contrib <= total + 1e-10
+                f"Branch {i} contribution exceeds total at some points"
-            ), 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"
@@ -778,6 +779,6 @@ class TestMultiBranchEdgeCases:
             assert integral > 0, f"Branch {i} has zero integral"
 
         # Sum of branch integrals should equal total
-        assert np.isclose(
+        assert np.isclose(sum(integrals), total_integral, rtol=1e-6), (
-            sum(integrals), total_integral, rtol=1e-6
+            "Sum of branch integrals should equal total integral"
-        ), "Sum of branch integrals should equal total integral"
+        )