Improving test coverage of registry.regtap.

(in an attempt to tackle #425).

This actually uncovered a bug in interpreting region_of_regard; since it
now comes out of VOTables, NULL and NaN are the same thing (since nobody
looks at region_of_regard, that certainly does not warrant a changelog
entry)

What is still uncovered is the deprecated ivoid2service, the obscure
region_of_regard, and some tedious piece of I/O.

pyvo/registry/regtap.py

@@ -539,7 +539,11 @@ def region_of_regard(self):
         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 val!=val:
+            return None
+        return val
 
     @property
     def waveband(self):
@@ -734,15 +738,16 @@ def search(self, *args, **keys):
 
         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):
         """

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 @@ def test_get_web_interface(self, flash_service):
         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 @@ def test_sia2_aux(self):
         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") == False
+
+    def test_supports_none(self):
+        intf = regtap.Interface("http://url", "", "", "")
+        assert intf.supports(None) == 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 @@ def test_select_single_matching_service(self):
             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()