Add more unit tests for ren_sv_coeffs

tests/test_scale_variations.py

@@ -29,6 +29,42 @@ def test_ren_sv_coeffs():
         scale_variations.ren_sv_coeffs(m=0, max_as=2, logpart=2, which_part=0, nf=5),
         0.0,
     )
+    # check all coeff are set
+    for m in (0, 1, 10):
+        for max_as in range(1, 3 + 1):
+            for logpart in range(1, max_as + 1):
+                for which_part in range(0, max_as - logpart + 1):
+                    for nf in (4, 5):
+                        c = scale_variations.ren_sv_coeffs(
+                            m=m,
+                            max_as=max_as,
+                            logpart=logpart,
+                            which_part=which_part,
+                            nf=nf,
+                        )
+                        assert np.isfinite(c)
+                        if which_part > 0 and not m == 0:
+                            assert c > 0.0
+                        else:
+                            assert c >= 0.0
+    # due to the exponential structure we can predict some things:
+    for nf in (4, 5):
+        # the highest log is always proportional beta0^k
+        for k in range(1, 3 + 1):
+            c = scale_variations.ren_sv_coeffs(
+                m=1, max_as=k, logpart=k, which_part=0, nf=nf
+            )
+            bare_c = c * (4.0 * np.pi / beta_qcd((2, 0), nf)) ** k
+            int_c = bare_c * np.math.factorial(k)
+            np.testing.assert_allclose(int_c, int(int_c))
+        # and even the second highest for the highest coeff
+        for k in range(2, 3 + 1):
+            c = scale_variations.ren_sv_coeffs(
+                m=1, max_as=k, logpart=k - 1, which_part=1, nf=nf
+            )
+            bare_c = c * (4.0 * np.pi / beta_qcd((2, 0), nf)) ** (k - 1)
+            int_c = bare_c * np.math.factorial(k)
+            np.testing.assert_allclose(int_c, int(int_c))
 
 
 def test_requirements():