Add integration test for Datadog::Tracing::Contrib::ViewComponent

* In order to properly write an integration test for ViewComponent
	we need to spin up an ad-hoc Rails app that we render the component
	within, then confirm the span data is generated
* The integration test includes the
	`datadog/tracing/contrib/rails/rails_helper`, which provides a
	`Rails test application` context
* Since there were configuration changes between different versions
	of ViewComponent, we need to adjust the configuration settings
	based on which version of the Gem has been loaded
	* This can be done using `Gem.loaded_specs` and `Gem::Version`,
		which provide an API for version comparison
	* Testing across the Appraised versions also checks that the
		`use_deprecated_instrumentation_name` configuration is applied,
		and does collect the necessary data

Author: tcannonfodder

spec/datadog/tracing/contrib/view_component/integration_test_spec.rb

@@ -0,0 +1,71 @@
+require 'datadog/tracing/contrib/rails/ext'
+require 'datadog/tracing/contrib/rails/rails_helper'
+require 'datadog/tracing/contrib/view_component/utils'
+require 'datadog/tracing/contrib/view_component/integration'
+
+
+require 'view_component'
+
+RSpec.describe 'ViewComponent integration tests', execute_in_fork: Rails.version.to_i >= 8 do
+  include_context 'Rails test application'
+  include ViewComponent::TestHelpers
+
+  let(:initialize_block) do
+    if Gem.loaded_specs["view_component"].version <= Gem::Version.new("3")
+      require "view_component/engine"
+    end
+
+    proc do
+      config.view_component.instrumentation_enabled = true
+      if Gem.loaded_specs["view_component"].version >= Gem::Version.new("4")
+        config.view_component.previews.controller = "TestController"
+      else
+        config.view_component.use_deprecated_instrumentation_name = false
+        config.view_component.test_controller = "TestController"
+      end
+    end
+  end
+
+  let(:component) do
+    stub_const("TestComponent", Class.new(ViewComponent::Base) do
+      def call
+        content_tag(:h1, "Hello")
+      end
+    end)
+  end
+
+  let(:controllers) { [controller] }
+
+  let(:controller) do
+    stub_const('TestController', Class.new(ActionController::Base))
+  end
+
+  before do
+    Datadog.configure do |c|
+      if Gem.loaded_specs["view_component"].version >= Gem::Version.new("3")
+        c.tracing.instrument :view_component
+      else
+        c.tracing.instrument :view_component, use_deprecated_instrumentation_name: true
+      end
+    end
+
+    allow(ENV).to receive(:[]).and_call_original
+
+    app
+  end
+
+  it "stores instrumentation data when rendering" do
+    controller.render(component.new)
+    span = spans.find{|s| s.name == "view_component.render" }
+
+    expect(span.name).to eq("view_component.render")
+    expect(span.resource).to eq("TestComponent")
+    expect(span.type).to eq(Datadog::Tracing::Metadata::Ext::HTTP::TYPE_TEMPLATE)
+
+    expect(span.get_tag(Datadog::Tracing::Metadata::Ext::TAG_COMPONENT)).to eq("view_component")
+    expect(span.get_tag(Datadog::Tracing::Metadata::Ext::TAG_OPERATION)).to eq("render")
+
+    expect(span.get_tag("view_component.component_name")).to eq("TestComponent")
+    expect(span.get_tag("view_component.component_identifier")).to eq("integration_test_spec.rb")
+  end
+end