improve s27 test and comment

tests/test_safsim.py

@@ -150,7 +150,7 @@ def test_c17_output_fault_class(alg, c17_resolved):
 
 
 # --------------------------------------------------------------------------- #
-# s27 fixture: exposes the exact-vs-optimistic difference between simulators.
+# s27 fixture: small sequential benchmark.
 # --------------------------------------------------------------------------- #
 
 def _s27_setup(s27_bench, s27_resolved):
@@ -158,7 +158,7 @@ def _s27_setup(s27_bench, s27_resolved):
     faults = list(fs.saf_equiv_classes.keys())
     rng = np.random.default_rng(1)
     pat = rng.choice([logic.ZERO, logic.ONE],
-                     size=(len(s27_resolved.s_nodes(KYUPY)), 64)).astype(np.uint8)
+                     size=(len(s27_resolved.s_nodes(KYUPY)), 8)).astype(np.uint8)
     return faults, pat
 
 
@@ -172,9 +172,9 @@ def test_s27_exact_simulators_agree(s27_bench, s27_resolved):
     # The two exact simulators must classify every fault identically.
     assert simple['DS'] == incr['DS']
     assert simple['NO'] == incr['NO']
-    # This deterministic pattern set leaves exactly one fault unobserved.
-    assert len(simple['DS']) == 31
-    assert len(simple['NO']) == 1
+    # This deterministic pattern set leaves exactly 6 faults unobserved.
+    assert len(simple['DS']) == 26
+    assert len(simple['NO']) == 6
 
 
 def test_s27_ppsfp_matches_exact(s27_bench, s27_resolved):
@@ -201,6 +201,7 @@ def test_ppsfp_multibranch_stem_observability(alg):
     r = classify(alg, c, [a_sa0], pat)
     assert r['DS'] == {a_sa0}
 
+
 @pytest.mark.parametrize('alg', [SAFSimIncremental, SAFSimPPSFP])
 def test_all_simprims(mydir, alg):
     c = verilog.load(mydir / 'all_kyupy_simprims.v')