Add test

spec/integration/container/providers/custom_provider_registrar_spec.rb

@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+RSpec.describe "Providers / Custom provider registrar" do
+  specify "Customizing the target_container for providers" do
+    # Create a provider registrar that exposes a container _wrapper_ (i.e. something resembling a
+    # Hanami slice) as the target_container.
+    provider_registrar = Class.new(Dry::System::ProviderRegistrar) do
+      def self.for_wrapper(wrapper)
+        Class.new(self) do
+          define_singleton_method(:new) do |container|
+            super(container, wrapper)
+          end
+        end
+      end
+
+      attr_reader :wrapper
+
+      def initialize(container, wrapper)
+        super(container)
+        @wrapper = wrapper
+      end
+
+      def target_container
+        wrapper
+      end
+    end
+
+    # Create the wrapper, which has an internal Dry::System::Container (configured with our custom
+    # provider_registrar) that it then delegates to.
+    container_wrapper = Class.new do
+      define_singleton_method(:container) do
+        @container ||= Class.new(Dry::System::Container).tap do |container|
+          container.config.provider_registrar = provider_registrar.for_wrapper(self)
+        end
+      end
+
+      def self.register_provider(...)
+        container.register_provider(...)
+      end
+
+      def self.start(...)
+        container.start(...)
+      end
+    end
+
+    # Create a provider to expose its given `target` so we can make expecations about it
+    exposed_target = nil
+    container_wrapper.register_provider(:my_provider) do
+      start do
+        exposed_target = target
+      end
+    end
+    container_wrapper.start(:my_provider)
+
+    expect(exposed_target).to be container_wrapper
+  end
+end