diff --git a/lib/openid/extensions/ax.rb b/lib/openid/extensions/ax.rb
index 007fe000..0afad1c6 100644
--- a/lib/openid/extensions/ax.rb
+++ b/lib/openid/extensions/ax.rb
@@ -539,9 +539,8 @@ def initialize(succeeded = true, error_message = nil)
       end
 
       def self.from_success_response(success_response)
-        resp = nil
         ax_args = success_response.message.get_args(NS_URI)
-        resp = ax_args.key?('error') ? new(false, ax_args['error']) : new
+        ax_args.key?('error') ? new(false, ax_args['error']) : new
       end
 
       def succeeded?
diff --git a/lib/openid/store/filesystem.rb b/lib/openid/store/filesystem.rb
index 0d5f2cea..cd9a038d 100644
--- a/lib/openid/store/filesystem.rb
+++ b/lib/openid/store/filesystem.rb
@@ -230,7 +230,7 @@ def mktemp
       # create a safe filename from a url
       def filename_escape(s)
         s = '' if s.nil?
-        filename_chunks = s.each_char.flat_map {|c|
+        s.each_char.flat_map {|c|
           @@FILENAME_ALLOWED.include?(c) ? c : c.bytes.map {|b|
             "_%02X" % b
           }
diff --git a/test/test_associationmanager.rb b/test/test_associationmanager.rb
index 47c22645..1d880292 100644
--- a/test/test_associationmanager.rb
+++ b/test/test_associationmanager.rb
@@ -304,7 +304,7 @@ def setup
     # server error or is otherwise undecipherable.
     def test_bad_response
       assert_log_matches('Server error when requesting an association') {
-        assert_equal(call_negotiate([mk_message({})]), nil)
+        assert_nil(call_negotiate([mk_message({})]))
       }
     end
 
@@ -320,7 +320,7 @@ def test_empty_assoc_type
                          "Server #{@server_url} responded with unsupported "\
                          "association session but did not supply a fallback."
                          ) {
-        assert_equal(call_negotiate([msg]), nil)
+        assert_nil(call_negotiate([msg]))
       }
 
     end
@@ -337,7 +337,7 @@ def test_empty_session_type
                          "Server #{@server_url} responded with unsupported "\
                          "association session but did not supply a fallback."
                          ) {
-        assert_equal(call_negotiate([msg]), nil)
+        assert_nil(call_negotiate([msg]))
       }
     end
 
@@ -357,7 +357,7 @@ def test_not_allowed
 
       assert_log_matches('Unsupported association type',
                          'Server sent unsupported session/association type:') {
-        assert_equal(call_negotiate([msg], negotiator), nil)
+        assert_nil(call_negotiate([msg], negotiator))
       }
     end
 
@@ -388,7 +388,7 @@ def test_unsupported_with_retry_and_fail
 
       assert_log_matches('Unsupported association type',
                          "Server #{@server_url} refused") {
-        assert_equal(call_negotiate([msg, msg]), nil)
+        assert_nil(call_negotiate([msg, msg]))
       }
     end
 
@@ -424,7 +424,7 @@ def setup
     def test_bad_response
       assert_log_matches('Server error when requesting an association') {
         response = call_negotiate([mk_message({})])
-        assert_equal(nil, response)
+        assert_nil(response)
       }
     end
 
@@ -436,7 +436,7 @@ def test_empty_assoc_type
 
       assert_log_matches('Server error when requesting an association') {
         response = call_negotiate([msg])
-        assert_equal(nil, response)
+        assert_nil(response)
       }
     end
 
@@ -448,7 +448,7 @@ def test_empty_session_type
 
       assert_log_matches('Server error when requesting an association') {
         response = call_negotiate([msg])
-        assert_equal(nil, response)
+        assert_nil(response)
       }
     end
 
@@ -466,7 +466,7 @@ def test_not_allowed
 
       assert_log_matches('Server error when requesting an association') {
         response = call_negotiate([msg])
-        assert_equal(nil, response)
+        assert_nil(response)
       }
     end
 
@@ -482,7 +482,7 @@ def test_unsupported_with_retry
 
       assert_log_matches('Server error when requesting an association') {
         response = call_negotiate([msg, assoc])
-        assert_equal(nil, response)
+        assert_nil(response)
       }
     end
 
@@ -818,13 +818,13 @@ def set_negotiate_response(assoc)
 
     def test_not_in_store_no_response
       set_negotiate_response(nil)
-      assert_equal(nil, @assoc_manager.get_association)
+      assert_nil(@assoc_manager.get_association)
     end
 
     def test_not_in_store_negotiate_assoc
       # Not stored beforehand:
       stored_assoc = @store.get_association(@server_url, @assoc.handle)
-      assert_equal(nil, stored_assoc)
+      assert_nil(stored_assoc)
 
       # Returned from associate call:
       set_negotiate_response(@assoc)
@@ -898,7 +898,7 @@ def test_success
     def test_missing_fields
       @message.del_arg(OPENID_NS, 'assoc_type')
       assert_log_matches('Missing required par') {
-        assert_equal(nil, make_request)
+        assert_nil(make_request)
       }
     end
 
@@ -907,7 +907,7 @@ def test_missing_fields
     def test_protocol_error
       @message.set_arg(OPENID_NS, 'expires_in', 'goats')
       assert_log_matches('Protocol error processing') {
-        assert_equal(nil, make_request)
+        assert_nil(make_request)
       }
     end
   end
diff --git a/test/test_ax.rb b/test/test_ax.rb
index b1cd399f..84ca7a48 100644
--- a/test/test_ax.rb
+++ b/test/test_ax.rb
@@ -47,7 +47,7 @@ def test_construct
         assert_equal(type_uri, ainfo.type_uri)
         assert_equal(1, ainfo.count)
         assert_equal(false, ainfo.required)
-        assert_equal(nil, ainfo.ns_alias)
+        assert_nil(ainfo.ns_alias)
       end
     end
 
@@ -234,7 +234,7 @@ def test_mode
 
       def test_construct
         assert_equal({}, @msg.requested_attributes)
-        assert_equal(nil, @msg.update_url)
+        assert_nil(@msg.update_url)
 
         msg = FetchRequest.new('hailstorm')
         assert_equal({}, msg.requested_attributes)
@@ -494,7 +494,7 @@ def setup
       end
 
       def test_construct
-        assert_equal(nil, @msg.update_url)
+        assert_nil(@msg.update_url)
         assert_equal({}, @msg.data)
       end
 
@@ -541,7 +541,7 @@ def test_update_url_in_response
       end
 
       def test_get_extension_args_single_value_response
-        # Single values do NOT have a count, and 
+        # Single values do NOT have a count, and
         # do not use the array extension
         eargs = {
           'mode' => 'fetch_response',
@@ -585,7 +585,7 @@ def test_get_single_success
       end
 
       def test_get_single_none
-        assert_equal(nil, @msg.get_single(@type_a))
+        assert_nil(@msg.get_single(@type_a))
       end
 
       def test_get_single_extra
diff --git a/test/test_consumer.rb b/test/test_consumer.rb
index 1e1dc7a0..6b524101 100644
--- a/test/test_consumer.rb
+++ b/test/test_consumer.rb
@@ -16,7 +16,7 @@ def test_set_get
           assert_equal(:endpoint, ep)
           consumer.send(:cleanup_last_requested_endpoint)
           ep = consumer.send(:last_requested_endpoint)
-          assert_equal(nil, ep)
+          assert_nil(ep)
         end
       end
 
diff --git a/test/test_discover.rb b/test/test_discover.rb
index da873728..6122513b 100644
--- a/test/test_discover.rb
+++ b/test/test_discover.rb
@@ -724,8 +724,8 @@ def test_isOPEndpoint
     end
 
     def test_noIdentifiers
-      assert_equal(@endpoint.get_local_id, nil)
-      assert_equal(@endpoint.claimed_id, nil)
+      assert_nil(@endpoint.get_local_id)
+      assert_nil(@endpoint.claimed_id)
     end
 
     def test_compatibility
@@ -733,7 +733,7 @@ def test_compatibility
     end
 
     def test_canonical_id
-      assert_equal(@endpoint.canonical_id, nil)
+      assert_nil(@endpoint.canonical_id)
     end
 
     def test_serverURL
diff --git a/test/test_discovery_manager.rb b/test/test_discovery_manager.rb
index 9a8abc22..e2185e90 100644
--- a/test/test_discovery_manager.rb
+++ b/test/test_discovery_manager.rb
@@ -21,8 +21,8 @@ def test_next
       assert_equal(@disco_services.next, @services[1])
       assert_equal(@disco_services.current, @services[1])
 
-      assert_equal(@disco_services.next, nil)
-      assert_equal(@disco_services.current, nil)
+      assert_nil(@disco_services.next)
+      assert_nil(@disco_services.current)
     end
 
     def test_for_url
@@ -84,7 +84,7 @@ def test_construct
     end
 
     def test_get_next_service
-      assert_equal(@session[@key], nil)
+      assert_nil(@session[@key])
 
       next_service = @manager.get_next_service {
         [@yadis_url, ["one", "two", "three"]]
@@ -123,24 +123,24 @@ def test_get_next_service
         ["unused", []]
       }
 
-      assert_equal(result, nil)
+      assert_nil(result)
     end
 
     def test_cleanup
       # With no preexisting manager, cleanup() returns nil.
-      assert_equal(@manager.cleanup, nil)
+      assert_nil(@manager.cleanup)
 
       # With a manager, it returns the manager's current service.
       disco = Consumer::DiscoveredServices.new(@url, @yadis_url, ["one", "two"])
 
       @session[@key] = disco
-      assert_equal(@manager.cleanup, nil)
-      assert_equal(@session[@key], nil)
+      assert_nil(@manager.cleanup)
+      assert_nil(@session[@key])
 
       disco.next
       @session[@key] = disco
       assert_equal(@manager.cleanup, "one")
-      assert_equal(@session[@key], nil)
+      assert_nil(@session[@key])
 
       # The force parameter should be passed through to get_manager
       # and destroy_manager.
@@ -178,7 +178,7 @@ def test_get_manager
       disco2 = Consumer::DiscoveredServices.new("http://not.this.url.com/",
                                                 "http://other.yadis.url/", ["one"])
       @session[@key] = disco2
-      assert_equal(@manager.get_manager, nil)
+      assert_nil(@manager.get_manager)
       assert_equal(@manager.get_manager(true), disco2)
     end
 
diff --git a/test/test_message.rb b/test/test_message.rb
index b7f6efb6..54416870 100644
--- a/test/test_message.rb
+++ b/test/test_message.rb
@@ -10,12 +10,14 @@ module GetArgsMixin
     # Tests a standard set of behaviors of Message.get_arg with
     # variations on handling defaults.
     def get_arg_tests(ns, key, expected=nil)
-      assert_equal(expected, @m.get_arg(ns, key))
-
       if expected.nil?
+        assert_nil(@m.get_arg(ns, key))
+
         assert_equal(@m.get_arg(ns, key, :a_default), :a_default)
         assert_raises(Message::KeyNotFound) { @m.get_arg(ns, key, NO_DEFAULT) }
       else
+        assert_equal(expected, @m.get_arg(ns, key))
+
         assert_equal(@m.get_arg(ns, key, :a_default), expected)
         assert_equal(@m.get_arg(ns, key, NO_DEFAULT), expected)
       end
@@ -73,7 +75,7 @@ def test_to_url
     end
 
     def test_get_openid
-      assert_equal(nil, @m.get_openid_namespace)
+      assert_nil(@m.get_openid_namespace)
     end
 
     def test_get_key_openid
@@ -87,15 +89,15 @@ def test_get_key_bare
     end
 
     def test_get_key_ns1
-      assert_equal(nil, @m.get_key(OPENID1_NS, 'foo'))
+      assert_nil(@m.get_key(OPENID1_NS, 'foo'))
     end
 
     def test_get_key_ns2
-      assert_equal(nil, @m.get_key(OPENID2_NS, 'foo'))
+      assert_nil(@m.get_key(OPENID2_NS, 'foo'))
     end
 
     def test_get_key_ns3
-      assert_equal(nil, @m.get_key('urn:something-special', 'foo'))
+      assert_nil(@m.get_key('urn:something-special', 'foo'))
     end
 
     def test_has_key
@@ -202,7 +204,7 @@ def test_set_arg
     def _test_set_arg_ns(ns)
       key = 'Camper Van Beethoven'
       value = 'David Lowery'
-      assert_equal(nil, @m.get_arg(ns, key))
+      assert_nil(@m.get_arg(ns, key))
       @m.set_arg(ns, key, value)
       assert_equal(value, @m.get_arg(ns, key))
     end
@@ -228,7 +230,7 @@ def test_del_arg
 
     def _test_del_arg_ns(ns)
       key = 'Fleeting Joys'
-      assert_equal(nil, @m.del_arg(ns, key))
+      assert_nil(@m.del_arg(ns, key))
     end
 
     def test_del_arg_bare
@@ -362,11 +364,11 @@ def test_get_key_ns1
     end
 
     def test_get_key_ns2
-      assert_equal(nil, @m.get_key(OPENID2_NS, 'mode'))
+      assert_nil(@m.get_key(OPENID2_NS, 'mode'))
     end
 
     def test_get_key_ns3
-      assert_equal(nil, @m.get_key('urn:xxx', 'mode'))
+      assert_nil(@m.get_key('urn:xxx', 'mode'))
     end
 
     def test_has_key
@@ -461,7 +463,7 @@ def test_update_args_ns3
     def _test_set_arg_ns(ns)
       key = 'awesometown'
       value = 'funny'
-      assert_equal(nil, @m.get_arg(ns,key))
+      assert_nil(@m.get_arg(ns,key))
       @m.set_arg(ns, key, value)
       assert_equal(value, @m.get_arg(ns,key))
     end
@@ -478,7 +480,7 @@ def _test_del_arg_ns(ns)
       @m.set_arg(ns, key, value)
       assert_equal(value, @m.get_arg(ns,key))
       @m.del_arg(ns,key)
-      assert_equal(nil, @m.get_arg(ns,key))
+      assert_nil(@m.get_arg(ns,key))
     end
 
     def test_del_arg; _test_del_arg_ns(OPENID_NS); end
@@ -702,7 +704,7 @@ def test_get_key_bare
     end
 
     def test_get_key_ns1
-      assert_equal(nil, @m.get_key(OPENID1_NS, 'mode'))
+      assert_nil(@m.get_key(OPENID1_NS, 'mode'))
     end
 
     def test_get_key_ns2
@@ -710,7 +712,7 @@ def test_get_key_ns2
     end
 
     def test_get_key_ns3
-      assert_equal(nil, @m.get_key('urn:xxx', 'mode'))
+      assert_nil(@m.get_key('urn:xxx', 'mode'))
     end
 
     def test_has_key_openid
@@ -739,11 +741,11 @@ def test_get_arg_openid
     end
 
     def test_get_arg_bare
-      assert_equal(nil, @m.get_arg(BARE_NS,'mode'))
+      assert_nil(@m.get_arg(BARE_NS,'mode'))
     end
 
     def test_get_arg_ns1
-      assert_equal(nil, @m.get_arg(OPENID1_NS,'mode'))
+      assert_nil(@m.get_arg(OPENID1_NS,'mode'))
     end
 
     def test_get_arg_ns2
@@ -751,7 +753,7 @@ def test_get_arg_ns2
     end
 
     def test_get_arg_ns3
-      assert_equal(nil, @m.get_arg('urn:bananastand','mode'))
+      assert_nil(@m.get_arg('urn:bananastand','mode'))
     end
 
     def test_get_args_openid
@@ -813,7 +815,7 @@ def test_update_args_ns3
     def _test_set_arg_ns(ns)
       key = "logan's"
       value = "run"
-      assert_equal(nil, @m.get_arg(ns,key))
+      assert_nil(@m.get_arg(ns,key))
       @m.set_arg(ns, key, value)
       assert_equal(value, @m.get_arg(ns,key))
     end
@@ -851,11 +853,11 @@ def test_from_post_args
     def _test_del_arg_ns(ns)
       key = 'no'
       value = 'socks'
-      assert_equal(nil, @m.get_arg(ns, key))
+      assert_nil(@m.get_arg(ns, key))
       @m.set_arg(ns, key, value)
       assert_equal(value, @m.get_arg(ns, key))
       @m.del_arg(ns, key)
-      assert_equal(nil, @m.get_arg(ns, key))
+      assert_nil(@m.get_arg(ns, key))
     end
 
     def test_del_arg_openid; _test_del_arg_ns(OPENID_NS); end
diff --git a/test/test_oauth.rb b/test/test_oauth.rb
index e37a8fa4..85a14e0a 100644
--- a/test/test_oauth.rb
+++ b/test/test_oauth.rb
@@ -143,7 +143,6 @@ def test_from_success_response
           'mode' => 'id_res',
           'ns' => OPENID2_NS,
           'ns.oauth' => OAuth::NS_URI,
-          'ns.oauth' => OAuth::NS_URI,
           'oauth.request_token' => 'REQUESTTOKEN',
           'oauth.scope' => "http://sample.com/some_scope"
         })
diff --git a/test/test_pape.rb b/test/test_pape.rb
index bd35bc78..a4309d8e 100644
--- a/test/test_pape.rb
+++ b/test/test_pape.rb
@@ -13,7 +13,7 @@ def setup
 
       def test_construct
         assert_equal([], @req.preferred_auth_policies)
-        assert_equal(nil, @req.max_auth_age)
+        assert_nil(@req.max_auth_age)
         assert_equal('pape', @req.ns_alias)
 
         req2 = PAPE::Request.new([PAPE::AUTH_MULTI_FACTOR], 1000)
@@ -53,7 +53,7 @@ def test_parse_extension_args
 
       def test_parse_extension_args_empty
         @req.parse_extension_args({})
-        assert_equal(nil, @req.max_auth_age)
+        assert_nil(@req.max_auth_age)
         assert_equal([], @req.preferred_auth_policies)
       end
 
@@ -110,9 +110,9 @@ def setup
 
       def test_construct
         assert_equal([], @req.auth_policies)
-        assert_equal(nil, @req.auth_time)
+        assert_nil(@req.auth_time)
         assert_equal('pape', @req.ns_alias)
-        assert_equal(nil, @req.nist_auth_level)
+        assert_nil(@req.nist_auth_level)
 
         req2 = PAPE::Response.new([PAPE::AUTH_MULTI_FACTOR], "1983-11-05T12:30:24Z", 3)
         assert_equal([PAPE::AUTH_MULTI_FACTOR], req2.auth_policies)
@@ -168,7 +168,7 @@ def test_parse_extension_args
 
       def test_parse_extension_args_empty
         @req.parse_extension_args({})
-        assert_equal(nil, @req.auth_time)
+        assert_nil(@req.auth_time)
         assert_equal([], @req.auth_policies)
       end
 
@@ -205,8 +205,8 @@ def test_parse_extension_args_nostrict_bogus
                 'nist_auth_level' => 'some'}
         @req.parse_extension_args(args)
         assert_equal(['http://foo','http://bar'], @req.auth_policies)
-        assert_equal(nil, @req.auth_time)
-        assert_equal(nil, @req.nist_auth_level)
+        assert_nil(@req.auth_time)
+        assert_nil(@req.nist_auth_level)
       end
 
 
diff --git a/test/test_responses.rb b/test/test_responses.rb
index a05275b0..0f2758b0 100644
--- a/test/test_responses.rb
+++ b/test/test_responses.rb
@@ -55,7 +55,7 @@ def test_extension_response_signed
           # Not all args in this NS are signed, so expect nil when
           # asking for them.
           utargs = resp.extension_response('urn:unittest', true)
-          assert_equal(nil, utargs)
+          assert_nil(utargs)
         end
       end
     end
diff --git a/test/test_server.rb b/test/test_server.rb
index 4c6da09d..f3b52558 100644
--- a/test/test_server.rb
+++ b/test/test_server.rb
@@ -142,7 +142,7 @@ def test_noReturnTo
     def test_no_message
       e = Server::ProtocolError.new(nil, "no message")
       assert(e.get_return_to.nil?)
-      assert_equal(e.which_encoding, nil)
+      assert_nil(e.which_encoding)
     end
 
     def test_which_encoding_no_message
@@ -167,7 +167,7 @@ def setup
     def test_none
       args = {}
       r = @decode.call(args)
-      assert_equal(r, nil)
+      assert_nil(r)
     end
 
     def test_irrelevant
@@ -350,7 +350,7 @@ def test_checkidSetupNoIdentityOpenID2
       assert(r.is_a?(Server::CheckIDRequest))
       assert_equal(r.mode, "checkid_setup")
       assert_equal(r.immediate, false)
-      assert_equal(r.identity, nil)
+      assert_nil(r.identity)
       assert_equal(r.trust_root, @tr_url)
       assert_equal(r.return_to, @rt_url)
     end
@@ -1896,9 +1896,9 @@ def test_unsupported
       response = @request.answer_unsupported(message)
       rfg = lambda { |f| response.fields.get_arg(OPENID_NS, f) }
       assert_equal(rfg.call('error_code'), 'unsupported-type')
-      assert_equal(rfg.call('assoc_type'), nil)
+      assert_nil(rfg.call('assoc_type'))
       assert_equal(rfg.call('error'), message)
-      assert_equal(rfg.call('session_type'), nil)
+      assert_nil(rfg.call('session_type'))
     end
 
     def test_openid1_unsupported_explode
@@ -2323,8 +2323,7 @@ def test_getAssocExpired
     def test_getAssocInvalid
       ah = 'no-such-handle'
       silence_logging {
-        assert_equal(
-                     @signatory.get_association(ah, false), nil)
+        assert_nil(@signatory.get_association(ah, false))
       }
       # assert(!@messages, @messages)
     end
@@ -2333,8 +2332,7 @@ def test_getAssocDumbVsNormal
       # getAssociation(dumb=False) cannot get a dumb assoc
       assoc_handle = makeAssoc(true)
       silence_logging {
-        assert_equal(
-                     @signatory.get_association(assoc_handle, false), nil)
+        assert_nil(@signatory.get_association(assoc_handle, false))
       }
       # @failIf(@messages, @messages)
     end
@@ -2348,8 +2346,7 @@ def test_getAssocNormalVsDumb
       #   MAC keys.
       assoc_handle = makeAssoc(false)
       silence_logging {
-        assert_equal(
-                     @signatory.get_association(assoc_handle, true), nil)
+        assert_nil(@signatory.get_association(assoc_handle, true))
       }
       # @failIf(@messages, @messages)
     end
diff --git a/test/test_sreg.rb b/test/test_sreg.rb
index d7790ca0..72defab1 100644
--- a/test/test_sreg.rb
+++ b/test/test_sreg.rb
@@ -154,7 +154,7 @@ def test_construct_empty
           req = Request.new
           assert_equal([], req.optional)
           assert_equal([], req.required)
-          assert_equal(nil, req.policy_url)
+          assert_nil(req.policy_url)
           assert_equal(NS_URI, req.ns_uri)
         end
 
@@ -476,4 +476,3 @@ def test_send_fields
     end
   end
 end
-
diff --git a/test/test_stores.rb b/test/test_stores.rb
index be42a846..4a039731 100644
--- a/test/test_stores.rb
+++ b/test/test_stores.rb
@@ -218,7 +218,7 @@ class FileStoreTestCase < Minitest::Test
       include StoreTestCase
 
       def setup
-        raise "filestoretest directory exists" if File.exists?('filestoretest')
+        raise "filestoretest directory exists" if File.exist?('filestoretest')
         @store = Filesystem.new('filestoretest')
       end
 
diff --git a/test/test_yadis_discovery.rb b/test/test_yadis_discovery.rb
index 0b83879d..434a020e 100644
--- a/test/test_yadis_discovery.rb
+++ b/test/test_yadis_discovery.rb
@@ -201,7 +201,7 @@ def test_is_xrds_neither
       def test_no_content_type
         with_fetcher(NoContentTypeFetcher.new) do
           result = Yadis.discover("http://bogus")
-          assert_equal(nil, result.content_type)
+          assert_nil(result.content_type)
         end
       end