diff --git a/spec/lib/appsignal/config_spec.rb b/spec/lib/appsignal/config_spec.rb
index 73a727f58..44f38a1df 100644
--- a/spec/lib/appsignal/config_spec.rb
+++ b/spec/lib/appsignal/config_spec.rb
@@ -405,7 +405,6 @@ def on_load
         :active => true,
         :push_api_key => "abc",
         :name => "TestApp",
-        :request_headers => kind_of(Array),
         :enable_minutely_probes => false
       )
     end
diff --git a/spec/lib/appsignal/hooks/activejob_spec.rb b/spec/lib/appsignal/hooks/activejob_spec.rb
index ca6dd2a5f..8624f9ae8 100644
--- a/spec/lib/appsignal/hooks/activejob_spec.rb
+++ b/spec/lib/appsignal/hooks/activejob_spec.rb
@@ -72,10 +72,11 @@
         ["perform_start.active_job", "perform.active_job"]
       end
     end
+    let(:options) { {} }
     before do
       ActiveJob::Base.queue_adapter = :inline
 
-      start_agent
+      start_agent(:options => options)
       Appsignal.internal_logger = test_logger(log)
       class ActiveJobTestJob < ActiveJob::Base
         def perform(*_args)
@@ -209,10 +210,9 @@ def perform(*_args)
       end
 
       context "with activejob_report_errors set to none" do
-        it "does not report the error" do
-          start_agent("production")
-          Appsignal.config[:activejob_report_errors] = "none"
+        let(:options) { { :activejob_report_errors => "none" } }
 
+        it "does not report the error" do
           allow(Appsignal).to receive(:increment_counter)
           tags = { :queue => queue }
           expect(Appsignal).to receive(:increment_counter)
@@ -228,10 +228,7 @@ def perform(*_args)
 
       if DependencyHelper.rails_version >= Gem::Version.new("7.1.0")
         context "with activejob_report_errors set to discard" do
-          before do
-            start_agent("production")
-            Appsignal.config[:activejob_report_errors] = "discard"
-          end
+          let(:options) { { :activejob_report_errors => "discard" } }
 
           it "does not report error on first failure" do
             with_test_adapter do
@@ -351,9 +348,9 @@ def perform(*_args)
     end
 
     context "with params" do
+      let(:options) { { :filter_parameters => ["foo"] } }
+
       it "filters the configured params" do
-        start_agent("production")
-        Appsignal.config[:filter_parameters] = ["foo"]
         queue_job(ActiveJobTestJob, method_given_args)
 
         transaction = last_transaction
diff --git a/spec/lib/appsignal/hooks/gvl_spec.rb b/spec/lib/appsignal/hooks/gvl_spec.rb
index 6b3e8bc43..b9fd54993 100644
--- a/spec/lib/appsignal/hooks/gvl_spec.rb
+++ b/spec/lib/appsignal/hooks/gvl_spec.rb
@@ -7,8 +7,9 @@
       end
     end
   else
+    let(:options) { {} }
     before do
-      start_agent
+      start_agent(:options => options)
     end
 
     def expect_gvltools_require
@@ -100,8 +101,9 @@ def self.enable
 
       describe "#install" do
         context "with enable_gvl_global_timer" do
+          let(:options) { { :enable_gvl_global_timer => true } }
+
           it "enables the GVL global timer" do
-            Appsignal.config[:enable_gvl_global_timer] = true
             expect(::GVLTools::GlobalTimer).to receive(:enable)
 
             described_class.new.install
@@ -109,8 +111,9 @@ def self.enable
         end
 
         context "without enable_gvl_global_timer" do
+          let(:options) { { :enable_gvl_global_timer => false } }
+
           it "does not enable the GVL global timer" do
-            Appsignal.config[:enable_gvl_global_timer] = false
             expect(::GVLTools::GlobalTimer).not_to receive(:enable)
 
             described_class.new.install
@@ -118,8 +121,9 @@ def self.enable
         end
 
         context "with enable_gvl_waiting_threads" do
+          let(:options) { { :enable_gvl_waiting_threads => true } }
+
           it "enables the GVL waiting threads" do
-            Appsignal.config[:enable_gvl_global_timer] = true
             expect(::GVLTools::WaitingThreads).to receive(:enable)
 
             described_class.new.install
@@ -127,8 +131,9 @@ def self.enable
         end
 
         context "without enable_gvl_waiting_threads" do
+          let(:options) { { :enable_gvl_waiting_threads => false } }
+
           it "does not enable the GVL waiting threads" do
-            Appsignal.config[:enable_gvl_waiting_threads] = false
             expect(::GVLTools::WaitingThreads).not_to receive(:enable)
 
             described_class.new.install
diff --git a/spec/lib/appsignal/hooks/http_spec.rb b/spec/lib/appsignal/hooks/http_spec.rb
index 07ace5cc8..f7c6384dc 100644
--- a/spec/lib/appsignal/hooks/http_spec.rb
+++ b/spec/lib/appsignal/hooks/http_spec.rb
@@ -1,7 +1,8 @@
 # frozen_string_literal: true
 
 describe Appsignal::Hooks::HttpHook do
-  before { start_agent }
+  let(:options) { {} }
+  before { start_agent(:options => options) }
 
   if DependencyHelper.http_present?
     context "with instrument_http_rb set to true" do
@@ -18,8 +19,7 @@
     end
 
     context "with instrument_http_rb set to false" do
-      before { Appsignal.config.config_hash[:instrument_http_rb] = false }
-      after { Appsignal.config.config_hash[:instrument_http_rb] = true }
+      let(:options) { { :instrument_http_rb => false } }
 
       describe "#dependencies_present?" do
         subject { described_class.new.dependencies_present? }
diff --git a/spec/lib/appsignal/hooks/net_http_spec.rb b/spec/lib/appsignal/hooks/net_http_spec.rb
index 2cb65bf99..8a96dd05d 100644
--- a/spec/lib/appsignal/hooks/net_http_spec.rb
+++ b/spec/lib/appsignal/hooks/net_http_spec.rb
@@ -1,5 +1,6 @@
 describe Appsignal::Hooks::NetHttpHook do
-  before { start_agent }
+  let(:options) { {} }
+  before { start_agent(:options => options) }
 
   describe "#dependencies_present?" do
     subject { described_class.new.dependencies_present? }
@@ -9,8 +10,7 @@
     end
 
     context "with Net::HTTP instrumentation disabled" do
-      before { Appsignal.config.config_hash[:instrument_net_http] = false }
-      after { Appsignal.config.config_hash[:instrument_net_http] = true }
+      let(:options) { { :instrument_net_http => false } }
 
       it { is_expected.to be_falsy }
     end
diff --git a/spec/lib/appsignal/hooks/rake_spec.rb b/spec/lib/appsignal/hooks/rake_spec.rb
index 6d4c8413b..2bdd95af6 100644
--- a/spec/lib/appsignal/hooks/rake_spec.rb
+++ b/spec/lib/appsignal/hooks/rake_spec.rb
@@ -4,8 +4,9 @@
   let(:helper) { Appsignal::Integrations::RakeIntegrationHelper }
   let(:task) { Rake::Task.new("task:name", Rake::Application.new) }
   let(:arguments) { Rake::TaskArguments.new(["foo"], ["bar"]) }
+  let(:options) { {} }
   before do
-    start_agent
+    start_agent(:options => options)
     allow(Kernel).to receive(:at_exit)
   end
   around { |example| keep_transactions { example.run } }
@@ -30,9 +31,7 @@ def perform
       end
 
       context "with :enable_rake_performance_instrumentation == false" do
-        before do
-          Appsignal.config[:enable_rake_performance_instrumentation] = false
-        end
+        let(:options) { { :enable_rake_performance_instrumentation => false } }
 
         it "creates no transaction" do
           expect { perform }.to_not(change { created_transactions.count })
@@ -49,9 +48,7 @@ def perform
       end
 
       context "with :enable_rake_performance_instrumentation == true" do
-        before do
-          Appsignal.config[:enable_rake_performance_instrumentation] = true
-        end
+        let(:options) { { :enable_rake_performance_instrumentation => true } }
 
         it "creates a transaction" do
           expect { perform }.to(change { created_transactions.count }.by(1))
diff --git a/spec/lib/appsignal/hooks/redis_client_spec.rb b/spec/lib/appsignal/hooks/redis_client_spec.rb
index 45ec7d432..888af0737 100644
--- a/spec/lib/appsignal/hooks/redis_client_spec.rb
+++ b/spec/lib/appsignal/hooks/redis_client_spec.rb
@@ -1,6 +1,7 @@
 describe Appsignal::Hooks::RedisClientHook do
+  let(:options) { {} }
   before do
-    start_agent
+    start_agent(:options => options)
   end
 
   if DependencyHelper.redis_client_present?
@@ -30,9 +31,7 @@
 
         context "with rest-client gem" do
           describe "integration" do
-            before do
-              Appsignal.config.config_hash[:instrument_redis] = true
-            end
+            let(:options) { { :instrument_redis => true } }
 
             context "install" do
               before do
@@ -115,9 +114,7 @@ def write(_commands)
         if DependencyHelper.hiredis_client_present?
           context "with hiredis driver" do
             describe "integration" do
-              before do
-                Appsignal.config.config_hash[:instrument_redis] = true
-              end
+              let(:options) { { :instrument_redis => true } }
 
               context "install" do
                 before do
@@ -200,9 +197,7 @@ def write(_commands)
       end
 
       context "with instrumentation disabled" do
-        before do
-          Appsignal.config.config_hash[:instrument_redis] = false
-        end
+        let(:options) { { :instrument_redis => false } }
 
         describe "#dependencies_present?" do
           subject { described_class.new.dependencies_present? }
diff --git a/spec/lib/appsignal/hooks/redis_spec.rb b/spec/lib/appsignal/hooks/redis_spec.rb
index 3f84ac099..a4edab721 100644
--- a/spec/lib/appsignal/hooks/redis_spec.rb
+++ b/spec/lib/appsignal/hooks/redis_spec.rb
@@ -1,5 +1,6 @@
 describe Appsignal::Hooks::RedisHook do
-  before { start_agent }
+  let(:options) { {} }
+  before { start_agent(:options => options) }
 
   if DependencyHelper.redis_present?
     context "with redis" do
@@ -22,9 +23,7 @@
           end
 
           describe "integration" do
-            before do
-              Appsignal.config.config_hash[:instrument_redis] = true
-            end
+            let(:options) { { :instrument_redis => true } }
 
             context "install" do
               before do
@@ -103,9 +102,7 @@ def write(_commands)
         end
 
         context "with instrumentation disabled" do
-          before do
-            Appsignal.config.config_hash[:instrument_redis] = false
-          end
+          let(:options) { { :instrument_redis => false } }
 
           describe "#dependencies_present?" do
             subject { described_class.new.dependencies_present? }
diff --git a/spec/lib/appsignal/hooks/resque_spec.rb b/spec/lib/appsignal/hooks/resque_spec.rb
index d9c155881..4327a85ad 100644
--- a/spec/lib/appsignal/hooks/resque_spec.rb
+++ b/spec/lib/appsignal/hooks/resque_spec.rb
@@ -25,8 +25,9 @@ def perform_rescue_job(klass, options = {})
 
       let(:queue) { "default" }
       let(:namespace) { Appsignal::Transaction::BACKGROUND_JOB }
+      let(:options) { {} }
       before do
-        start_agent
+        start_agent(:options => options)
 
         class ResqueTestJob
           def self.perform(*_args)
@@ -82,10 +83,7 @@ def self.perform
       end
 
       context "with arguments" do
-        before do
-          start_agent("production")
-          Appsignal.config[:filter_parameters] = ["foo"]
-        end
+        let(:options) { { :filter_parameters => ["foo"] } }
 
         it "filters out configured arguments" do
           perform_rescue_job(
diff --git a/spec/lib/appsignal/integrations/delayed_job_plugin_spec.rb b/spec/lib/appsignal/integrations/delayed_job_plugin_spec.rb
index 19cab5660..29144d9df 100644
--- a/spec/lib/appsignal/integrations/delayed_job_plugin_spec.rb
+++ b/spec/lib/appsignal/integrations/delayed_job_plugin_spec.rb
@@ -15,7 +15,8 @@ def self.plugins
     require "appsignal/integrations/delayed_job_plugin"
   end
   after(:context) { Object.send(:remove_const, :Delayed) }
-  before { start_agent }
+  let(:options) { {} }
+  before { start_agent(:options => options) }
 
   # We haven't found a way to test the hooks, we'll have to do that manually
 
@@ -82,10 +83,7 @@ def perform
         end
 
         context "with parameter filtering" do
-          before do
-            start_agent("production")
-            Appsignal.config[:filter_parameters] = ["foo"]
-          end
+          let(:options) { { :filter_parameters => ["foo"] } }
 
           it "filters selected arguments" do
             perform
@@ -271,10 +269,7 @@ def self.appsignal_name
             end
 
             context "with parameter filtering" do
-              before do
-                start_agent("production")
-                Appsignal.config[:filter_parameters] = ["foo"]
-              end
+              let(:options) { { :filter_parameters => ["foo"] } }
 
               it "filters selected arguments" do
                 perform
diff --git a/spec/lib/appsignal/integrations/shoryuken_spec.rb b/spec/lib/appsignal/integrations/shoryuken_spec.rb
index 4a68f3ec9..bc6df8a0b 100644
--- a/spec/lib/appsignal/integrations/shoryuken_spec.rb
+++ b/spec/lib/appsignal/integrations/shoryuken_spec.rb
@@ -9,7 +9,8 @@ class DemoShoryukenWorker
   let(:queue) { "some-funky-queue-name" }
   let(:sqs_msg) { double(:message_id => "msg1", :attributes => {}) }
   let(:body) { {} }
-  before { start_agent }
+  let(:options) { {} }
+  before { start_agent(:options => options) }
   around { |example| keep_transactions { example.run } }
 
   def perform_shoryuken_job(&block)
@@ -60,10 +61,7 @@ def perform_shoryuken_job(&block)
       end
 
       context "with parameter filtering" do
-        before do
-          start_agent("production")
-          Appsignal.config[:filter_parameters] = ["foo"]
-        end
+        let(:options) { { :filter_parameters => ["foo"] } }
 
         it "filters selected arguments" do
           perform_shoryuken_job
diff --git a/spec/lib/appsignal/integrations/sidekiq_spec.rb b/spec/lib/appsignal/integrations/sidekiq_spec.rb
index 83feac864..4829dc727 100644
--- a/spec/lib/appsignal/integrations/sidekiq_spec.rb
+++ b/spec/lib/appsignal/integrations/sidekiq_spec.rb
@@ -1,7 +1,11 @@
 require "appsignal/integrations/sidekiq"
 
 describe Appsignal::Integrations::SidekiqDeathHandler do
-  before { start_agent }
+  let(:options) { {} }
+  before do
+    stub_const("Sidekiq::VERSION", "7.1.0")
+    start_agent(:options => options)
+  end
   around { |example| keep_transactions { example.run } }
 
   let(:exception) do
@@ -28,10 +32,8 @@ def expect_no_error_on_transaction
   end
 
   context "when sidekiq_report_errors = none" do
-    before do
-      Appsignal.config[:sidekiq_report_errors] = "none"
-      call_handler
-    end
+    let(:options) { { :sidekiq_report_errors => "none" } }
+    before { call_handler }
 
     it "doesn't track the error on the transaction" do
       expect_no_error_on_transaction
@@ -39,10 +41,8 @@ def expect_no_error_on_transaction
   end
 
   context "when sidekiq_report_errors = all" do
-    before do
-      Appsignal.config[:sidekiq_report_errors] = "all"
-      call_handler
-    end
+    let(:options) { { :sidekiq_report_errors => "all" } }
+    before { call_handler }
 
     it "doesn't track the error on the transaction" do
       expect_no_error_on_transaction
@@ -50,10 +50,8 @@ def expect_no_error_on_transaction
   end
 
   context "when sidekiq_report_errors = discard" do
-    before do
-      Appsignal.config[:sidekiq_report_errors] = "discard"
-      call_handler
-    end
+    let(:options) { { :sidekiq_report_errors => "discard" } }
+    before { call_handler }
 
     it "records each occurrence of the error on the transaction" do
       expect_error_on_transaction
@@ -62,7 +60,8 @@ def expect_no_error_on_transaction
 end
 
 describe Appsignal::Integrations::SidekiqErrorHandler do
-  before { start_agent }
+  let(:options) { {} }
+  before { start_agent(:options => options) }
   around { |example| keep_transactions { example.run } }
 
   let(:exception) do
@@ -96,7 +95,7 @@ def expect_report_internal_error
     end
 
     context "when sidekiq_report_errors = none" do
-      before { Appsignal.config[:sidekiq_report_errors] = "none" }
+      let(:options) { { :sidekiq_report_errors => "none" } }
 
       it "tracks the error on a new transaction" do
         expect_report_internal_error
@@ -104,7 +103,7 @@ def expect_report_internal_error
     end
 
     context "when sidekiq_report_errors = all" do
-      before { Appsignal.config[:sidekiq_report_errors] = "all" }
+      let(:options) { { :sidekiq_report_errors => "all" } }
 
       it "tracks the error on a new transaction" do
         expect_report_internal_error
@@ -112,7 +111,7 @@ def expect_report_internal_error
     end
 
     context "when sidekiq_report_errors = discard" do
-      before { Appsignal.config[:sidekiq_report_errors] = "discard" }
+      let(:options) { { :sidekiq_report_errors => "discard" } }
 
       it "tracks the error on a new transaction" do
         expect_report_internal_error
@@ -143,10 +142,8 @@ def expect_no_error_on_transaction
     end
 
     context "when sidekiq_report_errors = none" do
-      before do
-        Appsignal.config[:sidekiq_report_errors] = "none"
-        call_handler
-      end
+      let(:options) { { :sidekiq_report_errors => "none" } }
+      before { call_handler }
 
       it "doesn't track the error on the transaction" do
         expect_no_error_on_transaction
@@ -155,10 +152,8 @@ def expect_no_error_on_transaction
     end
 
     context "when sidekiq_report_errors = all" do
-      before do
-        Appsignal.config[:sidekiq_report_errors] = "all"
-        call_handler
-      end
+      let(:options) { { :sidekiq_report_errors => "all" } }
+      before { call_handler }
 
       it "records each occurrence of the error on the transaction" do
         expect_error_on_transaction
@@ -167,10 +162,8 @@ def expect_no_error_on_transaction
     end
 
     context "when sidekiq_report_errors = discard" do
-      before do
-        Appsignal.config[:sidekiq_report_errors] = "discard"
-        call_handler
-      end
+      let(:options) { { :sidekiq_report_errors => "discard" } }
+      before { call_handler }
 
       it "doesn't track the error on the transaction" do
         expect_no_error_on_transaction
@@ -222,8 +215,9 @@ class DelayedTestClass; end
   end
   let(:plugin) { Appsignal::Integrations::SidekiqMiddleware.new }
   let(:log) { StringIO.new }
+  let(:options) { {} }
   before do
-    start_agent
+    start_agent(:options => options)
     Appsignal.internal_logger = test_logger(log)
   end
   around { |example| keep_transactions { example.run } }
@@ -242,10 +236,7 @@ class DelayedTestClass; end
   end
 
   context "with parameter filtering" do
-    before do
-      start_agent("production")
-      Appsignal.config[:filter_parameters] = ["foo"]
-    end
+    let(:options) { { :filter_parameters => ["foo"] } }
 
     it "filters selected arguments" do
       perform_sidekiq_job
@@ -384,7 +375,6 @@ class DelayedTestClass; end
       include RailsHelper
 
       it "reports the worker name as the action, copies the namespace and tags" do
-        start_agent("production")
         with_rails_error_reporter do
           perform_sidekiq_job do
             Appsignal.tag_job("test_tag" => "value")
diff --git a/spec/lib/appsignal/transaction_spec.rb b/spec/lib/appsignal/transaction_spec.rb
index 98b23781a..ac0d6c558 100644
--- a/spec/lib/appsignal/transaction_spec.rb
+++ b/spec/lib/appsignal/transaction_spec.rb
@@ -1,8 +1,9 @@
 describe Appsignal::Transaction do
+  let(:options) { {} }
   let(:time) { Time.at(fixed_time) }
 
   before do
-    start_agent
+    start_agent(:options => options)
     Timecop.freeze(time)
   end
   after { Timecop.return }
@@ -323,7 +324,7 @@
       end
 
       context "with AppSignal filtering" do
-        before { Appsignal.config.config_hash[:filter_parameters] = %w[foo] }
+        let(:options) { { :filter_parameters => %w[foo] } }
 
         it "returns sanitized custom params" do
           transaction.set_params("foo" => "value", "baz" => "bat")
@@ -439,12 +440,15 @@
         expect(transaction).to include_session_data(arg_data)
       end
 
-      it "does not include filtered out session data" do
-        Appsignal.config[:filter_session_data] = ["filtered_key"]
-        transaction.set_session_data("data" => "value1", "filtered_key" => "filtered_value")
+      context "with filter_session_data" do
+        let(:options) { { :filter_session_data => ["filtered_key"] } }
 
-        transaction._sample
-        expect(transaction).to include_session_data("data" => "value1")
+        it "does not include filtered out session data" do
+          transaction.set_session_data("data" => "value1", "filtered_key" => "filtered_value")
+
+          transaction._sample
+          expect(transaction).to include_session_data("data" => "value1")
+        end
       end
 
       it "logs an error if an error occurred storing the session data" do
@@ -563,12 +567,15 @@
         expect(transaction).to include_environment(arg_data)
       end
 
-      it "does not include filtered out headers" do
-        Appsignal.config[:request_headers] = ["MY_HEADER"]
-        transaction.set_headers("MY_HEADER" => "value1", "filtered_key" => "filtered_value")
+      context "with request_headers options" do
+        let(:options) { { :request_headers => ["MY_HEADER"] } }
 
-        transaction._sample
-        expect(transaction).to include_environment("MY_HEADER" => "value1")
+        it "does not include filtered out headers" do
+          transaction.set_headers("MY_HEADER" => "value1", "filtered_key" => "filtered_value")
+
+          transaction._sample
+          expect(transaction).to include_environment("MY_HEADER" => "value1")
+        end
       end
 
       it "logs an error if an error occurred storing the headers" do
@@ -975,8 +982,7 @@
     end
 
     context "when filter_metadata includes metadata key" do
-      before { Appsignal.config[:filter_metadata] = ["filter_key"] }
-      after { Appsignal.config[:filter_metadata] = [] }
+      let(:options) { { :filter_metadata => ["filter_key"] } }
 
       it "does not set the metadata on the transaction" do
         transaction.set_metadata(:filter_key, "filtered value")
diff --git a/spec/support/fixtures/projects/valid/config/appsignal.yml b/spec/support/fixtures/projects/valid/config/appsignal.yml
index 8a345a432..a8b467a54 100644
--- a/spec/support/fixtures/projects/valid/config/appsignal.yml
+++ b/spec/support/fixtures/projects/valid/config/appsignal.yml
@@ -1,13 +1,6 @@
 default: &defaults
   push_api_key: "abc"
   name: "TestApp"
-  request_headers: [
-    "HTTP_ACCEPT", "HTTP_ACCEPT_CHARSET", "HTTP_ACCEPT_ENCODING",
-    "HTTP_ACCEPT_LANGUAGE", "HTTP_CACHE_CONTROL", "HTTP_CONNECTION",
-    "CONTENT_LENGTH", "PATH_INFO", "HTTP_RANGE", "HTTP_REFERER",
-    "REQUEST_METHOD", "REQUEST_PATH", "SERVER_NAME", "SERVER_PORT",
-    "SERVER_PROTOCOL", "HTTP_USER_AGENT"
-  ]
   enable_minutely_probes: false
 
 production:
diff --git a/spec/support/helpers/config_helpers.rb b/spec/support/helpers/config_helpers.rb
index 9e4d83c53..184faa5b9 100644
--- a/spec/support/helpers/config_helpers.rb
+++ b/spec/support/helpers/config_helpers.rb
@@ -1,4 +1,8 @@
 module ConfigHelpers
+  def with_config(_options)
+    A
+  end
+
   def project_fixture_path
     File.expand_path(
       File.join(File.dirname(__FILE__), "../fixtures/projects/valid")
@@ -22,8 +26,8 @@ def project_fixture_config( # rubocop:disable Metrics/ParameterLists
   end
   module_function :project_fixture_config, :project_fixture_path
 
-  def start_agent(env = "production")
-    Appsignal._config = project_fixture_config(env)
+  def start_agent(env: "production", options: {})
+    Appsignal._config = project_fixture_config(env, options)
     Appsignal.start
   end
 end