diff --git a/pyvo/registry/regtap.py b/pyvo/registry/regtap.py
index 4fb5f2c..89f1355 100644
--- a/pyvo/registry/regtap.py
+++ b/pyvo/registry/regtap.py
@@ -25,6 +25,8 @@ from astropy import table
 from astropy.utils.decorators import deprecated
 from astropy.utils.exceptions import AstropyDeprecationWarning
 
+import numpy
+
 from . import rtcons
 from ..dal import scs, sia, sia2, ssa, sla, tap, query as dalq
 from ..io.vosi import vodataservice
@@ -539,7 +541,11 @@ class RegistryResource(dalq.Record):
         by which a positional query against this resource should be "blurred"
         in order to get an appropriate match.
         """
-        return float(self.get("region_of_regard", 0))
+        # we get NULLs as NaNs here
+        val = self["region_of_regard"]
+        if numpy.isnan(val):
+            return None
+        return val
 
     @property
     def waveband(self):
@@ -734,15 +740,16 @@ class RegistryResource(dalq.Record):
 
         Raises
         ------
-        RuntimeError
+        DALServiceError
            if the resource does not describe a searchable service.
         """
-        if not self.service:
+        try:
+            return self.service.search(*args, **keys)
+        except ValueError:
+            # I blindly assume the ValueError comes out of get_interface.
+            # But then that's likely enough.
             raise dalq.DALServiceError(
-                "resource, {}, is not a searchable service".format(
-                    self.short_name))
-
-        return self.service.search(*args, **keys)
+                f"Resource {self.ivoid} is not a searchable service")
 
     def describe(self, verbose=False, width=78, file=None):
         """

diff --git a/pyvo/registry/tests/test_regtap.py b/pyvo/registry/tests/test_regtap.py
index a534c70..622604c 100644
--- a/pyvo/registry/tests/test_regtap.py
+++ b/pyvo/registry/tests/test_regtap.py
@@ -383,6 +383,7 @@ def test_record_fields(rt_pulsar_distance):
     assert rec.content_types == ['catalog']
     assert rec.source_format == "bibcode"
     assert rec.source_value == "1993ApJS...88..529T"
+    assert rec.region_of_regard is None
     assert rec.waveband == ['radio']
     # access URL, standard_id and friends exercised in TestInterfaceSelection
 
@@ -453,6 +454,17 @@ class TestInterfaceSelection:
         assert (svc.access_url
                 == "http://dc.zah.uni-heidelberg.de/flashheros/q/web/form")
 
+        import webbrowser
+        orig_open = webbrowser.open
+        try:
+            open_args = []
+            webbrowser.open = lambda *args: open_args.append(args)
+            svc.search()
+            assert open_args == [
+                ("http://dc.zah.uni-heidelberg.de/flashheros/q/web/form", 2)]
+        finally:
+            webbrowser.open = orig_open
+
     def test_get_aux_interface(self, flash_service):
         svc = flash_service.get_service("tap#aux")
         assert (svc._baseurl
@@ -540,6 +552,22 @@ class TestInterfaceSelection:
         assert rec.get_interface("sia2").access_url == 'http://sia2.example.com'
         assert rec.get_interface("sia").access_url == 'http://sia.example.com'
 
+    def test_non_standard_interface(self):
+        intf = regtap.Interface("http://url", "", "", "")
+        assert intf.supports("ivo://ivoa.net/std/sia") is False
+
+    def test_supports_none(self):
+        intf = regtap.Interface("http://url", "", "", "")
+        assert intf.supports(None) is False
+
+    def test_non_searchable_service(self):
+        rec = _makeRegistryRecord()
+        with pytest.raises(dalq.DALServiceError) as excinfo:
+            rec.search()
+
+        assert str(excinfo.value) == (
+            "Resource ivo://pyvo/test_regtap.py is not a searchable service")
+
 
 class _FakeResult:
     """A fake class just sufficient for giving dal.query.Record enough
@@ -623,6 +651,9 @@ class TestInterfaceRejection:
             intf_roles=["", "std"])
 
         assert (rsc.service._baseurl == "http://b")
+        # this makes sure caching the service obtained doesn't break
+        # things
+        assert (rsc.service._baseurl == "http://b")
 
     def test_capless(self):
         rsc = _makeRegistryRecord()

MAINT: improve test coverage of regtap
Currently, it's only 55% with missing coverage of numerous methods leading to wonder whether hash-based splitting of standardid works as intended for services with IDs including a hash, e.g. the distinction of SIA and SIA2.


https://github.com/astropy/pyvo/blob/main/pyvo/registry/regtap.py#L311
https://github.com/astropy/pyvo/blob/main/pyvo/registry/regtap.py#L338
pyvo/registry/tests/test_regtap.py::test_record_fields pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_non_searchable_service
pyvo/registry/tests/test_regtap.py::TestInterfaceClass::test_basic pyvo/registry/tests/test_regtap.py::TestInterfaceClass::test_repr pyvo/registry/tests/test_regtap.py::TestInterfaceClass::test_unknown_standard pyvo/registry/tests/test_regtap.py::TestInterfaceClass::test_known_standard pyvo/registry/tests/test_regtap.py::TestInterfaceClass::test_secondary_interface pyvo/registry/tests/test_regtap.py::TestInterfaceClass::test_VOSI pyvo/registry/tests/test_regtap.py::test_keywords pyvo/registry/tests/test_regtap.py::test_single_keyword pyvo/registry/tests/test_regtap.py::test_servicetype pyvo/registry/tests/test_regtap.py::test_waveband pyvo/registry/tests/test_regtap.py::test_datamodel pyvo/registry/tests/test_regtap.py::test_servicetype_aux pyvo/registry/tests/test_regtap.py::test_bad_servicetype_aux pyvo/registry/tests/test_regtap.py::test_spatial pyvo/registry/tests/test_regtap.py::test_spectral pyvo/registry/tests/test_regtap.py::test_to_table pyvo/registry/tests/test_regtap.py::TestResultIndexing::test_get_with_index pyvo/registry/tests/test_regtap.py::TestResultIndexing::test_get_with_short_name pyvo/registry/tests/test_regtap.py::TestResultIndexing::test_get_with_ivoid pyvo/registry/tests/test_regtap.py::TestResultIndexing::test_out_of_range pyvo/registry/tests/test_regtap.py::TestResultIndexing::test_bad_key pyvo/registry/tests/test_regtap.py::TestResultIndexing::test_not_indexable pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_exactly_one_result pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_access_modes pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_standard_id_multi pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_get_web_interface pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_get_aux_interface pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_get_aux_as_main pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_get__main_from_aux pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_get_by_alias pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_get_unsupported_standard pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_get_nonexisting_standard pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_unconstrained pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_interface_without_role pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_sia2_query pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_sia2_aux pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_non_standard_interface pyvo/registry/tests/test_regtap.py::TestInterfaceSelection::test_supports_none pyvo/registry/tests/test_regtap.py::TestInterfaceRejection::test_nonunique pyvo/registry/tests/test_regtap.py::TestInterfaceRejection::test_nonunique_lax pyvo/registry/tests/test_regtap.py::TestInterfaceRejection::test_nonstd_ignored pyvo/registry/tests/test_regtap.py::TestInterfaceRejection::test_select_single_matching_service pyvo/registry/tests/test_regtap.py::TestInterfaceRejection::test_capless pyvo/registry/tests/test_regtap.py::TestExtraResourceMethods::test_unique_standard_id pyvo/registry/tests/test_regtap.py::TestExtraResourceMethods::test_describe_multi pyvo/registry/tests/test_regtap.py::TestExtraResourceMethods::test_no_access_url pyvo/registry/tests/test_regtap.py::TestExtraResourceMethods::test_unique_access_url pyvo/registry/tests/test_regtap.py::TestExtraResourceMethods::test_ambiguous_access_url_warns