diff --git a/.travis.yml b/.travis.yml
index 3e17ac6..59bdc60 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,20 +1,17 @@
 language: ruby
-bundler_args: --without debug
 script: "bundle exec rspec spec"
-before_install: "gem update --system"
 env:
   - CI=true
 rvm:
-  - 2.2
-  - 2.3
   - 2.4
   - 2.5
-  - jruby-9
-  - rbx-3
+  - 2.6
+  - 2.7
+  - jruby
 cache: bundler
 sudo: false
 matrix:
   allow_failures:
-    - rvm: jruby-9
-    - rvm: rbx-3
+    - rvm: jruby
+    - rvm: 2.7
 dist: trusty
diff --git a/Gemfile b/Gemfile
index a78d207..b2d5b08 100644
--- a/Gemfile
+++ b/Gemfile
@@ -10,6 +10,6 @@ group :debug do
 end
 
 group :development, :test do
-  gem 'simplecov',  require: false, platform: :mri
-  gem 'coveralls',  require: false, platform: :mri
+  gem 'simplecov',  platforms: :mri
+  gem 'coveralls',  '~> 0.8', platforms: :mri
 end
\ No newline at end of file
diff --git a/VERSION b/VERSION
index 4a36342..fd2a018 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-3.0.0
+3.1.0
diff --git a/lib/rdf/spec/enumerable.rb b/lib/rdf/spec/enumerable.rb
index 7e934e8..b8ca852 100644
--- a/lib/rdf/spec/enumerable.rb
+++ b/lib/rdf/spec/enumerable.rb
@@ -7,25 +7,24 @@
     raise 'enumerable must be set with `let(:enumerable)' unless
       defined? enumerable
 
-    @statements ||= RDF::Spec.quads
+    @rdf_enumerable_iv_statements ||= RDF::Spec.quads
 
     if enumerable.empty?
       if (enumerable.writable? rescue false)
-        enumerable.insert(*@statements)
+        enumerable.insert(*@rdf_enumerable_iv_statements)
       elsif enumerable.respond_to?(:<<)
-        @statements.each { |statement| enumerable << statement }
+        @rdf_enumerable_iv_statements.each { |statement| enumerable << statement }
       else
         raise "@enumerable must respond to #<< or be pre-populated with the statements in #{RDF::Spec::TRIPLES_FILE} in a before(:each) block"
       end
     end
-
-    @supports_named_graphs = enumerable.supports?(:graph_name) rescue true
   end
 
-  let(:subject_count) {@statements.map(&:subject).uniq.length}
-  let(:bnode_subject_count) {@statements.map(&:subject).uniq.select(&:node?).length}
-  let(:non_bnode_statements) {@statements.reject(&:node?)}
-  let(:non_bnode_terms) {@statements.map(&:to_quad).flatten.compact.reject(&:node?).uniq}
+  let(:supports_named_graphs) {enumerable.supports?(:graph_name) rescue true}
+  let(:subject_count) {@rdf_enumerable_iv_statements.map(&:subject).uniq.length}
+  let(:bnode_subject_count) {@rdf_enumerable_iv_statements.map(&:subject).uniq.select(&:node?).length}
+  let(:non_bnode_statements) {@rdf_enumerable_iv_statements.reject(&:node?)}
+  let(:non_bnode_terms) {@rdf_enumerable_iv_statements.map(&:to_quad).flatten.compact.reject(&:node?).uniq}
 
   subject { enumerable }
   it {is_expected.to respond_to(:supports?)}
@@ -57,9 +56,9 @@
     it {is_expected.to respond_to(:empty?)}
     it {is_expected.to_not be_empty}
     it {is_expected.to respond_to(:count)}
-    its(:count) {is_expected.to eq @statements.size}
+    its(:count) {is_expected.to eq @rdf_enumerable_iv_statements.size}
     it {is_expected.to respond_to(:size)}
-    its(:size) {is_expected.to eq @statements.size}
+    its(:size) {is_expected.to eq @rdf_enumerable_iv_statements.size}
 
     context "and empty" do
       subject {[].extend(RDF::Enumerable)}
@@ -74,7 +73,7 @@
     its(:statements) {is_expected.to be_a(Array)}
 
     context "#statements" do
-      specify {expect(subject.statements.size).to eq @statements.size}
+      specify {expect(subject.statements.size).to eq @rdf_enumerable_iv_statements.size}
       specify {expect(subject.statements).to all(be_a_statement)}
     end
 
@@ -89,7 +88,7 @@
       end
 
       it "does not have statement in different named graph" do
-        if @supports_named_graphs
+        if supports_named_graphs
           graph_name = RDF::URI.new("urn:graph_name:1")
           non_bnode_statements.each do |statement|
             s = statement.dup
@@ -132,7 +131,7 @@
 
     its(:triples) {is_expected.to be_a(Array)}
     context "#triples" do
-      specify {expect(subject.triples.size).to eq @statements.size}
+      specify {expect(subject.triples.size).to eq @rdf_enumerable_iv_statements.size}
       specify {expect(subject.triples).to all(be_a_triple)}
     end
 
@@ -176,13 +175,13 @@
 
     its(:quads) {is_expected.to be_a(Array)}
     context "#quads" do
-      specify {expect(subject.quads.size).to eq @statements.size}
+      specify {expect(subject.quads.size).to eq @rdf_enumerable_iv_statements.size}
       specify {expect(subject.quads).to all(be_a_quad)}
     end
 
     context "#has_quad?" do
       specify do
-        if @supports_named_graphs
+        if supports_named_graphs
           non_bnode_statements.each do |statement|
             is_expected.to have_quad(statement.to_quad)
           end
@@ -265,7 +264,7 @@
   end
 
   context "when enumerating predicates" do
-    let(:predicates) {@statements.map { |s| s.predicate }.uniq}
+    let(:predicates) {@rdf_enumerable_iv_statements.map { |s| s.predicate }.uniq}
     it {is_expected.to respond_to(:predicates)}
     it {is_expected.to respond_to(:has_predicate?)}
     it {is_expected.to respond_to(:each_predicate)}
@@ -285,7 +284,7 @@
     context "#has_predicate?" do
       specify do
         checked = []
-        @statements.each do |statement|
+        @rdf_enumerable_iv_statements.each do |statement|
           expect(enumerable).to have_predicate(statement.predicate) unless checked.include?(statement.predicate)
           checked << statement.predicate
         end
@@ -434,8 +433,8 @@
     end
 
     it "should implement #has_graph?" do
-      if @supports_named_graphs
-        @statements.each do |statement|
+      if supports_named_graphs
+        @rdf_enumerable_iv_statements.each do |statement|
           if statement.has_graph?
             expect(enumerable).to have_graph(statement.graph_name)
           end
@@ -480,21 +479,21 @@
 
       context "non-existing graph" do
         let(:graph_name) {RDF::URI.new('http://example.org/does/not/have/this/uri')}
-        specify {expect(subject.project_graph(graph_name)).to be_empty if @supports_named_graphs}
+        specify {expect(subject.project_graph(graph_name)).to be_empty if supports_named_graphs}
       end
     end
 
     its(:each_graph) {is_expected.to be_an_enumerator}
 
     describe "#each_graph" do
-      let(:graph_names) {@statements.map { |s| s.graph_name }.uniq.compact}
+      let(:graph_names) {@rdf_enumerable_iv_statements.map { |s| s.graph_name }.uniq.compact}
       subject { enumerable.each_graph }
       it {is_expected.to be_an_enumerator}
-      specify {is_expected.to all(be_a_graph) if @supports_named_graphs}
+      specify {is_expected.to all(be_a_graph) if supports_named_graphs}
  
       it "has appropriate number of graphs" do
-        if @supports_named_graphs
-          graph_names = @statements.map { |s| s.graph_name }.uniq.compact
+        if supports_named_graphs
+          graph_names = @rdf_enumerable_iv_statements.map { |s| s.graph_name }.uniq.compact
           expect(subject.to_a.size).to eq (graph_names.size + 1)
         end
       end
@@ -505,7 +504,7 @@
       it {is_expected.to be_an_enumerator}
       it {is_expected.to be_countable}
       it "enumerates the same as #each_graph" do
-        expect(subject.to_a).to include(*enumerable.each_graph.to_a) if @supports_named_graphs # expect with match problematic
+        expect(subject.to_a).to include(*enumerable.each_graph.to_a) if supports_named_graphs # expect with match problematic
       end
     end
   end
diff --git a/lib/rdf/spec/http_adapter.rb b/lib/rdf/spec/http_adapter.rb
index 97ba7b8..917026e 100644
--- a/lib/rdf/spec/http_adapter.rb
+++ b/lib/rdf/spec/http_adapter.rb
@@ -63,6 +63,24 @@
       end
     end
 
+    it "adds User-Agent header using default" do
+      WebMock.stub_request(:get, uri).with do |request|
+        expect(request.headers['User-Agent']).to eq "Ruby RDF.rb/#{RDF::VERSION}"
+      end.to_return(body: "foo")
+      RDF::Util::File.open_file(uri) do |f|
+        opened.opened
+      end
+    end
+
+    it "used provided User-Agent header" do
+      WebMock.stub_request(:get, uri).with do |request|
+        expect(request.headers["User-Agent"]).to eq "Foo"
+      end.to_return(body: "foo")
+      RDF::Util::File.open_file(uri, headers: {"User-Agent" => "Foo"}) do |f|
+        opened.opened
+      end
+    end
+
     it "sets content_type and encoding to utf-8 if absent" do
       WebMock.stub_request(:get, uri).to_return(body: "foo", headers: {"Content-Type" => "text/turtle"})
       RDF::Util::File.open_file(uri) do |f|
diff --git a/lib/rdf/spec/inspects.rb b/lib/rdf/spec/inspects.rb
index cca56d1..2e36617 100644
--- a/lib/rdf/spec/inspects.rb
+++ b/lib/rdf/spec/inspects.rb
@@ -31,38 +31,6 @@ def inspect
   end
 end
 
-class Array
-  alias_method :inspect_without_formatting, :inspect
-  def inspect_with_formatting
-    if all? { |item| item.is_a?(Hash) }
-      string = "[\n"
-      each do |item|
-        string += "  {\n"
-          item.keys.sort_by(&:to_s).each do |key|
-            string += "      #{key.inspect}: #{item[key].inspect}\n"
-          end
-        string += "  },\n"
-      end
-      string += "]"
-      string
-    elsif all? { |item| item.is_a?(RDF::Query::Solution)}
-      string = "[\n"
-      each do |item|
-        string += "  {\n"
-          item.bindings.keys.sort_by(&:to_s).each do |key|
-            string += "      #{key.inspect}: #{item.bindings[key].inspect}\n"
-          end
-        string += "  },\n"
-      end
-      string += "]"
-      string
-    else
-      inspect_without_formatting
-    end
-  end
-  alias_method :inspect, :inspect_with_formatting
-end
-
 class RDF::Query::Solutions
   def inspect
     string = "vars: #{variable_names.join(",")}\n#{to_a.inspect}"
diff --git a/lib/rdf/spec/matchers.rb b/lib/rdf/spec/matchers.rb
index 9e05746..ee2e20e 100644
--- a/lib/rdf/spec/matchers.rb
+++ b/lib/rdf/spec/matchers.rb
@@ -1,4 +1,5 @@
 require 'rspec/matchers' # @see http://rubygems.org/gems/rspec
+require 'awesome_print'
 
 module RDF; module Spec
   ##
@@ -187,17 +188,17 @@ module Matchers
     RSpec::Matchers.define :write_each do |*messages|
       supports_block_expectations { true }
 
-      match do |block|
+      match(notify_expectation_failures: true) do |block|
         messages.each { |message| expect(&block).to write(message) }
       end
     end
 
     RSpec::Matchers.define :write do |message|
-      chain(:to) { |io| @io = io }
+      chain(:to) { |io| @rdf_matcher_iv_io = io }
 
       supports_block_expectations { true }
 
-      match do |block|
+      match(notify_expectation_failures: true) do |block|
         @output =
           case io
           when :output then fake_stdout(&block)
@@ -256,7 +257,7 @@ def fake_stdout
 
       # default IO is standard output
       def io
-        @io ||= :output
+        @rdf_matcher_iv_io ||= :output
       end
 
       # IO name is used for description message
@@ -265,7 +266,7 @@ def io_name
       end
     end
 
-    Info = Struct.new(:id, :logger, :action, :result)
+    Info = Struct.new(:id, :logger, :action, :result, :format)
 
     RSpec::Matchers.define :be_equivalent_graph do |expected, info|
       match do |actual|
@@ -274,21 +275,21 @@ def io_name
         elsif info.is_a?(Logger)
           Info.new("", info)
         elsif info.is_a?(Hash)
-          Info.new(info[:id], info[:logger], info[:action], info[:result])
+          Info.new(info[:id], info[:logger], info[:action], info[:result], info[:format])
         else
           Info.new(info)
         end
+        @info.format ||= case
+        when RDF.const_defined?(:TriG) then :trig
+        when RDF.const_defined?(:Turtle) then :ttl
+        else :nquads
+        end
         @expected = normalize(expected)
         @actual = normalize(actual)
         @actual.isomorphic_with?(@expected) rescue false
       end
 
       failure_message do |actual|
-        format = case
-        when RDF.const_defined?(:TriG) then :trig
-        when RDF.const_defined?(:Turtle) then :ttl
-        else :nquads
-        end
         info = @info.respond_to?(:information) ? @info.information : @info.inspect
         if @expected.is_a?(RDF::Enumerable) && @actual.size != @expected.size
           "Graph entry counts differ:\nexpected: #{@expected.size}\nactual:   #{@actual.size}\n"
@@ -296,8 +297,8 @@ def io_name
           "Graphs differ\n"
         end +
         "\n#{info + "\n" unless info.empty?}" +
-        "Expected:\n#{@expected.dump(format, standard_prefixes: true, literal_shorthand: false, validate: false) rescue @expected.inspect}" +
-        "Results:\n#{@actual.dump(format, standard_prefixes: true, literal_shorthand: false, validate: false) rescue @actual.inspect}" +
+        "Expected:\n#{@expected.dump(@info.format, standard_prefixes: true, literal_shorthand: false, validate: false) rescue @expected.inspect}" +
+        "Results:\n#{@actual.dump(@info.format, standard_prefixes: true, literal_shorthand: false, validate: false) rescue @actual.inspect}" +
         "\nDebug:\n#{@info.logger}"
       end
 
@@ -310,7 +311,7 @@ def io_name
         info = @info.respond_to?(:information) ? @info.information : @info.inspect
         "Graphs identical\n" +
         "\n#{info + "\n" unless info.empty?}" +
-        "Results:\n#{actual.dump(format, standard_prefixes: true, literal_shorthand: false, validate: false) rescue @actual.inspect}" +
+        "Results:\n#{actual.dump(@info.format, standard_prefixes: true, literal_shorthand: false, validate: false) rescue @actual.inspect}" +
         "\nDebug:\n#{@info.logger}"
       end
 
@@ -329,15 +330,6 @@ def normalize(graph)
       end
     end
 
-    require 'json'
-    JSON_STATE = ::JSON::State.new(
-       indent:        "  ",
-       space:         " ",
-       space_before:  "",
-       object_nl:     "\n",
-       array_nl:      "\n"
-     )
-
     RSpec::Matchers.define :produce do |expected, info|
       match do |actual|
         @info = if (info.id rescue false)
@@ -355,8 +347,8 @@ def normalize(graph)
       failure_message do |actual|
         info = @info.respond_to?(:information) ? @info.information : @info.inspect
 
-        "Expected: #{expected.is_a?(String) ? expected : expected.to_json(JSON_STATE) rescue 'malformed json'}\n" +
-        "Actual  : #{actual.is_a?(String) ? actual : actual.to_json(JSON_STATE) rescue 'malformed json'}\n" +
+        "Expected: #{expected.ai}\n" +
+        "Actual  : #{actual.ai}\n" +
         "\n#{info + "\n" unless info.empty?}" +
         "\nDebug:\n#{@info.logger}"
       end
@@ -365,7 +357,7 @@ def normalize(graph)
         info = @info.respond_to?(:information) ? @info.information : @info.inspect
 
         "Expected not to produce the following:\n" + 
-        "Actual  : #{actual.is_a?(String) ? actual : actual.to_json(JSON_STATE) rescue 'malformed json'}\n" +
+        "Actual  : #{actual.ai}\n" +
         "\n#{info + "\n" unless info.empty?}" +
         "\nDebug:\n#{@info.logger}"
       end
diff --git a/lib/rdf/spec/mutable.rb b/lib/rdf/spec/mutable.rb
index 1611a73..c8275bb 100644
--- a/lib/rdf/spec/mutable.rb
+++ b/lib/rdf/spec/mutable.rb
@@ -9,14 +9,14 @@
       defined? mutable
 
     skip "Immutable resource" unless mutable.mutable?
-    @statements = RDF::Spec.triples
+    @rdf_mutable_iv_statements = RDF::Spec.triples
     @supports_named_graphs = mutable.respond_to?(:supports?) && mutable.supports?(:graph_name)
     @supports_literal_equality = mutable.respond_to?(:supports?) && mutable.supports?(:literal_equality)
   end
 
   let(:resource) { RDF::URI('http://rubygems.org/gems/rdf') }
   let(:graph_name) { RDF::URI('http://example.org/graph_name') }
-  let(:non_bnode_statements) {@statements.reject(&:node?)}
+  let(:non_bnode_statements) {@rdf_mutable_iv_statements.reject(&:node?)}
 
   describe RDF::Mutable do
     subject { mutable }
@@ -56,7 +56,7 @@
       end
 
       it "should accept an optional hash argument" do
-        expect { subject.load(RDF::Spec::TRIPLES_FILE, {}) }.not_to raise_error
+        expect { subject.load(RDF::Spec::TRIPLES_FILE, **{}) }.not_to raise_error
       end
 
       it "should load statements" do
@@ -69,7 +69,7 @@
         if @supports_named_graphs
           subject.load RDF::Spec::TRIPLES_FILE, graph_name: graph_name
           is_expected.to have_graph(graph_name)
-          expect(subject.query(graph_name: graph_name).size).to eq subject.size
+          expect(subject.query({graph_name: graph_name}).size).to eq subject.size
         end
       end
     end
@@ -139,7 +139,7 @@
 
     context "when deleting statements" do
       before :each do
-        subject.insert(*@statements)
+        subject.insert(*@rdf_mutable_iv_statements)
       end
 
       it "should not raise errors" do
@@ -152,7 +152,7 @@
       end
 
       it "should support deleting multiple statements at a time" do
-        subject.delete(*@statements)
+        subject.delete(*@rdf_mutable_iv_statements)
         expect(subject.find { |s| subject.has_statement?(s) }).to be_nil
       end
 
@@ -234,13 +234,13 @@
         end
 
         it 'deletes and inserts' do
-          subject.delete_insert(@statements, [statement])
+          subject.delete_insert(@rdf_mutable_iv_statements, [statement])
           is_expected.to contain_exactly statement
         end
 
         it 'deletes before inserting' do
-          subject.delete_insert(@statements, [@statements.first])
-          is_expected.to contain_exactly @statements.first
+          subject.delete_insert(@rdf_mutable_iv_statements, [@rdf_mutable_iv_statements.first])
+          is_expected.to contain_exactly @rdf_mutable_iv_statements.first
         end
 
         it 'deletes patterns' do
@@ -276,7 +276,7 @@
             if subject.mutable? && subject.supports?(:atomic_write)
               contents = subject.statements.to_a
 
-              expect { subject.delete_insert(@statements, [nil]) }
+              expect { subject.delete_insert(@rdf_mutable_iv_statements, [nil]) }
                 .to raise_error ArgumentError
               expect(subject.statements).to contain_exactly(*contents)
             end
diff --git a/lib/rdf/spec/queryable.rb b/lib/rdf/spec/queryable.rb
index 510bc56..8aa0846 100644
--- a/lib/rdf/spec/queryable.rb
+++ b/lib/rdf/spec/queryable.rb
@@ -7,16 +7,16 @@
     raise 'querable must be set with `let(:queryable)' unless
       defined? queryable
 
-    @doap = RDF::Spec::QUADS_FILE
-    @statements = RDF::Spec.quads
+    @rdf_queryable_iv_doap = RDF::Spec::QUADS_FILE
+    @rdf_queryable_iv_statements = RDF::Spec.quads
 
     if queryable.empty?
       if (queryable.writable? rescue false)
-        queryable.insert(*@statements)
+        queryable.insert(*@rdf_queryable_iv_statements)
       elsif queryable.respond_to?(:<<)
-        @statements.each { |statement| queryable << statement }
+        @rdf_queryable_iv_statements.each { |statement| queryable << statement }
       else
-        raise "queryable must respond to #<< or be pre-populated with the statements in #{@doap} in a before(:each) block"
+        raise "queryable must respond to #<< or be pre-populated with the statements in #{@rdf_queryable_iv_doap} in a before(:each) block"
       end
     end
   end
@@ -95,7 +95,7 @@
           pattern = RDF::Query::Pattern.new(nil, nil, nil, graph_name: nil)
           solutions = []
           subject.send(method, pattern) {|s| solutions << s}
-          expect(solutions.size).to eq @statements.size
+          expect(solutions.size).to eq @rdf_queryable_iv_statements.size
         end
 
         it "returns statements from named graphs with variable graph_name" do
@@ -114,7 +114,7 @@
             pattern = RDF::Query::Pattern.new(nil, nil, nil, graph_name: RDF::URI("http://ar.to/#self"))
             solutions = []
             subject.send(method, pattern) {|s| solutions << s}
-            expect(solutions.size).to eq File.readlines(@doap).grep(/^<http:\/\/ar.to\/\#self>/).size
+            expect(solutions.size).to eq File.readlines(@rdf_queryable_iv_doap).grep(/^<http:\/\/ar.to\/\#self>/).size
           end
         end
       end
@@ -233,22 +233,22 @@
             end
 
             it "returns the correct number of results for array queries" do
-              expect(subject.query([nil, nil, nil]).size).to eq @statements.size
-              expect(subject.query([resource, nil, nil]).size).to eq File.readlines(@doap).grep(/^<http:\/\/rubygems\.org\/gems\/rdf>/).size
-              expect(subject.query([RDF::URI("http://ar.to/#self"), nil, nil]).size).to eq File.readlines(@doap).grep(/^<http:\/\/ar.to\/\#self>/).size
+              expect(subject.query([nil, nil, nil]).size).to eq @rdf_queryable_iv_statements.size
+              expect(subject.query([resource, nil, nil]).size).to eq File.readlines(@rdf_queryable_iv_doap).grep(/^<http:\/\/rubygems\.org\/gems\/rdf>/).size
+              expect(subject.query([RDF::URI("http://ar.to/#self"), nil, nil]).size).to eq File.readlines(@rdf_queryable_iv_doap).grep(/^<http:\/\/ar.to\/\#self>/).size
               expect(subject.query([resource, RDF::URI("http://usefulinc.com/ns/doap#name"), nil]).size).to eq 1
               expect(subject.query([nil, nil, RDF::URI("http://usefulinc.com/ns/doap#Project")]).size).to eq 1
             end
 
             it "returns the correct number of results for hash queries" do
-              expect(subject.query({}).size).to eq @statements.size
-              expect(subject.query(subject: resource).size).to eq File.readlines(@doap).grep(/^<http:\/\/rubygems\.org\/gems\/rdf>/).size
-              expect(subject.query(subject: resource, predicate: RDF::URI("http://usefulinc.com/ns/doap#name")).size).to eq 1
-              expect(subject.query(object: RDF::URI("http://usefulinc.com/ns/doap#Project")).size).to eq 1
+              expect(subject.query({}).size).to eq @rdf_queryable_iv_statements.size
+              expect(subject.query({subject: resource}).size).to eq File.readlines(@rdf_queryable_iv_doap).grep(/^<http:\/\/rubygems\.org\/gems\/rdf>/).size
+              expect(subject.query({subject: resource, predicate: RDF::URI("http://usefulinc.com/ns/doap#name")}).size).to eq 1
+              expect(subject.query({object: RDF::URI("http://usefulinc.com/ns/doap#Project")}).size).to eq 1
             end
 
             it "returns the correct number of results for query queries" do
-              expect(subject.query(query).size).to eq @statements.size
+              expect(subject.query(query).size).to eq @rdf_queryable_iv_statements.size
             end
           end
         end
@@ -256,13 +256,13 @@
         context "with specific patterns from SPARQL" do
           context "triple pattern combinations" do
             it "?s p o" do
-              expect(subject.query(predicate: RDF::URI("http://example.org/p"), object: RDF::Literal.new(1)).to_a).to(
+              expect(subject.query({predicate: RDF::URI("http://example.org/p"), object: RDF::Literal.new(1)}).to_a).to(
                 include *[RDF::Statement.new(RDF::URI("http://example.org/xi1"), RDF::URI("http://example.org/p"), 1), RDF::Statement.new(RDF::URI("http://example.org/xi2"), RDF::URI("http://example.org/p"), 1)]
               )
             end
 
             it "s ?p o" do
-              expect(subject.query(subject: RDF::URI("http://example.org/xi2"), object: RDF::Literal.new(1)).to_a).to(
+              expect(subject.query({subject: RDF::URI("http://example.org/xi2"), object: RDF::Literal.new(1)}).to_a).to(
                 include *[RDF::Statement.new(RDF::URI("http://example.org/xi2"), RDF::URI("http://example.org/p"), 1)]
               )
             end
@@ -272,8 +272,8 @@
           context "data/r2/expr-equals" do
             context "graph-1" do
               let(:result) do
-                queryable.query(predicate: RDF::URI("http://example.org/p"),
-                                object: RDF::Literal::Integer.new(1)).to_a
+                queryable.query({predicate: RDF::URI("http://example.org/p"),
+                                 object: RDF::Literal::Integer.new(1)}).to_a
               end
 
               it 'has two solutions' do
@@ -293,8 +293,8 @@
 
             context "graph-2" do
               let(:result) do
-                queryable.query(predicate: RDF::URI("http://example.org/p"),
-                                object: RDF::Literal::Double.new("1.0e0"))
+                queryable.query({predicate: RDF::URI("http://example.org/p"),
+                                 object: RDF::Literal::Double.new("1.0e0")})
                   .to_a
               end
 
diff --git a/lib/rdf/spec/reader.rb b/lib/rdf/spec/reader.rb
index 42a4d10..2871b41 100644
--- a/lib/rdf/spec/reader.rb
+++ b/lib/rdf/spec/reader.rb
@@ -207,7 +207,7 @@
       expect(reader_mock).to receive(:got_here)
       reader_class.new(reader_input, prefixes: {a: "b"}) do |r|
         reader_mock.got_here
-        expect(r.prefixes).to eq({a: "b"})
+        expect(r.prefixes).to include({a: "b"})
       end
     end
   end
diff --git a/lib/rdf/spec/repository.rb b/lib/rdf/spec/repository.rb
index fbedb16..eeea688 100644
--- a/lib/rdf/spec/repository.rb
+++ b/lib/rdf/spec/repository.rb
@@ -7,9 +7,8 @@
     raise 'repository must be set with `let(:repository)' unless
       defined? repository
 
-    @statements = RDF::Spec.quads
     if repository.empty? && repository.writable?
-      repository.insert(*@statements)
+      repository.insert(*RDF::Spec.quads)
     elsif repository.empty?
       raise "+@repository+ must respond to #<< or be pre-populated with the statements in #{RDF::Spec::TRIPLES_FILE} in a before(:each) block"
     end
diff --git a/lib/rdf/spec/transactable.rb b/lib/rdf/spec/transactable.rb
index 8d2a35b..8e60b5c 100644
--- a/lib/rdf/spec/transactable.rb
+++ b/lib/rdf/spec/transactable.rb
@@ -3,7 +3,7 @@
 RSpec.shared_examples 'an RDF::Transactable' do
   include RDF::Spec::Matchers
 
-  let(:statements) { RDF::Spec.quads }
+  let(:statements) { @rdf_transactable_iv_statements = RDF::Spec.quads }
 
   before do
     raise '`transactable` must be set with `let(:transactable)`' unless
@@ -34,7 +34,7 @@
 
       expect do
         subject.transaction(mutable: true) do
-          delete(*@statements)
+          delete(*statements)
           raise 'my error'
         end
       end.to raise_error RuntimeError
diff --git a/lib/rdf/spec/transaction.rb b/lib/rdf/spec/transaction.rb
index ef9ca0f..b7a681c 100644
--- a/lib/rdf/spec/transaction.rb
+++ b/lib/rdf/spec/transaction.rb
@@ -212,10 +212,10 @@
         with_name = st.dup
         with_name.graph_name = graph_uri
 
-        expect do 
+        expect do
           subject.insert(st)
           subject.execute
-        end.to change { subject.repository }
+        end.to change { subject.repository.statements }
 
         expect(subject.repository).to have_statement(with_name)
       end
diff --git a/lib/rdf/spec/writer.rb b/lib/rdf/spec/writer.rb
index d0182c5..92d515a 100644
--- a/lib/rdf/spec/writer.rb
+++ b/lib/rdf/spec/writer.rb
@@ -13,6 +13,27 @@
   let(:reader_class) { writer_class.format.reader}
   let(:format_class) { writer_class.format }
 
+  let(:graph) do
+    @rdf_writer_iv_graph ||= begin
+      n1 = RDF::Node("a")
+      n2 = RDF::Node("a")
+      p = RDF::URI("http://example/pred")
+      s1 = RDF::Statement(n1, p, n1)
+      s2 = RDF::Statement(n2, p, n2)
+      s3 = RDF::Statement(n1, p, n2)
+      s4 = RDF::Statement(n2, p, n1)
+      RDF::Graph.new.insert(s1, s2, s3, s4)
+    end
+  end
+
+  let(:serialized) do
+    @rdf_writer_iv_serialized ||= begin
+      writer_class.buffer do |w|
+        w << graph
+      end
+    end
+  end
+
   describe ".each" do
     it "yields each writer" do
       writer_class.each do |r|
@@ -31,18 +52,6 @@
 
     it "should serialize different BNodes sharing a common identifier to using different BNode ids" do
       if reader_class
-        n1 = RDF::Node("a")
-        n2 = RDF::Node("a")
-        p = RDF::URI("http://example/pred")
-        s1 = RDF::Statement(n1, p, n1)
-        s2 = RDF::Statement(n2, p, n2)
-        s3 = RDF::Statement(n1, p, n2)
-        s4 = RDF::Statement(n2, p, n1)
-        graph = RDF::Graph.new.insert(s1, s2, s3, s4)
-        expect(graph.count).to eql 4
-        serialized = writer_class.buffer do |w|
-          w << graph
-        end
         expect(serialized).not_to be_empty
         graph2 = RDF::Graph.new do |g|
           g << reader_class.new(serialized)
@@ -50,25 +59,43 @@
         expect(graph2.count).to eql 4
       end
     end
+
+    it "returns a string" do
+      expect(serialized).to be_a(String)
+    end
+
+    it "should use encoding defined for format by default" do
+      writer_class.new do |w|
+        expect(serialized.encoding).to eql w.encoding
+      end
+    end
+
+    it "should use provided encoding if specified" do
+      str = writer_class.buffer(encoding: Encoding::ASCII_8BIT) do |w|
+        w << graph
+      end
+
+      expect(str.encoding).to eql Encoding::ASCII_8BIT
+    end
   end
 
   describe ".open" do
     before(:each) do
       allow(RDF::Util::File).to receive(:open_file).and_yield(StringIO.new("foo"))
-      @dir = Dir.mktmpdir
-      @basename = File.join(@dir, "foo")
+      @rdf_writer_iv_dir = Dir.mktmpdir
+      @rdf_writer_iv_basename = File.join(@rdf_writer_iv_dir, "foo")
     end
 
     after(:each) do
-      FileUtils.rm_rf(@dir)
+      FileUtils.rm_rf(@rdf_writer_iv_dir)
     end
 
     it "yields writer given file_name" do
       format_class.file_extensions.each_pair do |sym, content_type|
         writer_mock = double("writer")
         expect(writer_mock).to receive(:got_here)
-        expect(writer_class).to receive(:for).with(file_name: "#{@basename}.#{sym}").and_return(writer_class)
-        writer_class.open("#{@basename}.#{sym}") do |r|
+        expect(writer_class).to receive(:for).with(file_name: "#{@rdf_writer_iv_basename}.#{sym}").and_return(writer_class)
+        writer_class.open("#{@rdf_writer_iv_basename}.#{sym}") do |r|
           expect(r).to be_a(RDF::Writer)
           writer_mock.got_here
         end
@@ -80,7 +107,7 @@
       writer_mock = double("writer")
       expect(writer_mock).to receive(:got_here)
       expect(writer_class).to receive(:for).with(sym).and_return(writer_class)
-      writer_class.open("#{@basename}.#{sym}", format: sym) do |r|
+      writer_class.open("#{@rdf_writer_iv_basename}.#{sym}", format: sym) do |r|
         expect(r).to be_a(RDF::Writer)
         writer_mock.got_here
       end
@@ -90,8 +117,8 @@
       format_class.file_extensions.each_pair do |sym, content_type|
         writer_mock = double("writer")
         expect(writer_mock).to receive(:got_here)
-        expect(writer_class).to receive(:for).with(file_name: "#{@basename}.#{sym}").and_return(writer_class)
-        writer_class.open("#{@basename}.#{sym}", file_name: "#{@basename}.#{sym}") do |r|
+        expect(writer_class).to receive(:for).with(file_name: "#{@rdf_writer_iv_basename}.#{sym}").and_return(writer_class)
+        writer_class.open("#{@rdf_writer_iv_basename}.#{sym}", file_name: "#{@rdf_writer_iv_basename}.#{sym}") do |r|
           expect(r).to be_a(RDF::Writer)
           writer_mock.got_here
         end
@@ -102,8 +129,8 @@
       format_class.content_types.each_pair do |content_type, formats|
         writer_mock = double("writer")
         expect(writer_mock).to receive(:got_here)
-        expect(writer_class).to receive(:for).with(content_type: content_type, file_name: @basename).and_return(writer_class)
-        writer_class.open(@basename, content_type: content_type) do |r|
+        expect(writer_class).to receive(:for).with(content_type: content_type, file_name: @rdf_writer_iv_basename).and_return(writer_class)
+        writer_class.open(@rdf_writer_iv_basename, content_type: content_type) do |r|
           expect(r).to be_a(RDF::Writer)
           writer_mock.got_here
         end
diff --git a/rdf-spec.gemspec b/rdf-spec.gemspec
index 6519f41..4f8d23e 100755
--- a/rdf-spec.gemspec
+++ b/rdf-spec.gemspec
@@ -16,21 +16,16 @@ Gem::Specification.new do |gem|
 
   gem.platform           = Gem::Platform::RUBY
   gem.files              = %w(AUTHORS CREDITS README.md UNLICENSE VERSION) + Dir.glob('etc/*') + Dir.glob('lib/**/*.rb') + Dir.glob('spec/*.rb')
-  gem.bindir             = %q(bin)
-  gem.executables        = %w()
-  gem.default_executable = gem.executables.first
   gem.require_paths      = %w(lib)
-  gem.extensions         = %w()
-  gem.test_files         = %w()
-  gem.has_rdoc           = false
 
-  gem.required_ruby_version      = '>= 2.2.2'
+  gem.required_ruby_version      = '>= 2.4'
   gem.requirements               = []
-  gem.add_runtime_dependency     'rdf',             '~> 3.0'
+  gem.add_runtime_dependency     'rdf',             '~> 3.1'
+  gem.add_runtime_dependency     'awesome_print',   '~> 1.8'
   gem.add_runtime_dependency     'rdf-isomorphic',  '~> 3.0'
-  gem.add_runtime_dependency     'rspec',           '~> 3.7'
-  gem.add_runtime_dependency     'rspec-its',       '~> 1.2'
-  gem.add_runtime_dependency     'webmock',         '~> 3.1'
-  gem.add_development_dependency 'yard' ,           '~> 0.9.12'
-  gem.post_install_message       = nil
+  gem.add_runtime_dependency     'rspec',           '~> 3.9'
+  gem.add_runtime_dependency     'rspec-its',       '~> 1.3'
+  gem.add_runtime_dependency     'webmock',         '~> 3.7'
+  gem.add_development_dependency 'yard' ,           '~> 0.9.20'
+  gem.post_install_message        = nil
 end
diff --git a/spec/transaction_spec.rb b/spec/transaction_spec.rb
index 770cff8..afead26 100644
--- a/spec/transaction_spec.rb
+++ b/spec/transaction_spec.rb
@@ -1,7 +1,8 @@
 require File.join(File.dirname(__FILE__), 'spec_helper')
 require 'rdf/spec/transaction'
 
-describe RDF::Transaction, skip: "pending fixes to immutability errors" do
+describe RDF::Transaction do
+  let(:repository) { RDF::Repository.new }
   # @see lib/rdf/spec/transaction.rb in rdf-spec
   it_behaves_like "an RDF::Transaction", RDF::Transaction
 end