Add a test which used to fail (crash)

test/unit_tests/hoc_python/test_refcounts.py

@@ -0,0 +1,26 @@
+from neuron import h
+import sys
+
+
+def test_seg_from_sec_x_ref():
+    """A reproducer of calling `seg_from_sec_x` without a Python Section
+
+    Without the fix generally we would get (upon interpreter exit)
+       Fatal Python error: bool_dealloc: "deallocating True or False: bug likely caused by a refcount error in a C extension"
+    """
+    ## Pure python (ok)
+    # soma1 = nrn.Section("soma1")
+    # nc1 = h.NetCon(soma1(0.5)._ref_v, None)
+    # seg1 = nc1.preseg()
+    # print(sys.getrefcount(seg1))
+    # print(sys.getrefcount(seg1.sec))
+
+    h("create soma")
+    h("objref nc")
+    h("objref nil")
+    h('soma nc = new NetCon(&v(0.5), nil)')
+    nc = h.nc
+    seg = nc.preseg()  # uses `seg_from_sec_x`
+
+    assert sys.getrefcount(seg) == 2
+    assert sys.getrefcount(seg.sec) == 3