fix(copyable): do not mutate input params

lib/convenient_service/support/copyable.rb

@@ -20,8 +20,12 @@ module Copyable
       #   NOTE: This method is NOT likely to be ever changed, that is why inline logic is preferred over command classes in this particular case.
       #
       def copy(overrides: {})
-        overrides[:args] ||= {}
-        overrides[:kwargs] ||= {}
+        defaults = {args: {}, kwargs: {}}
+
+        ##
+        # IMPORTANT: Do not mutate `overrides`.
+        #
+        overrides = defaults.merge(overrides)
 
         ##
         # TODO: Refactor runtime `respond_to?`. Investigate before refactoring.

spec/lib/convenient_service/support/copyable_spec.rb

@@ -83,6 +83,14 @@ def to_block
         expect(instance).to have_received(:to_block)
       end
 
+      context "when `overrides[:args]` is NOT passed" do
+        let(:overrides) { {} }
+
+        it "defaults to empty hash`" do
+          expect(instance.copy(overrides: overrides).args).to eq(constructor_params[:args])
+        end
+      end
+
       context "when `overrides[:args]` is passed" do
         context "when `overrides[:args]` is array" do
           let(:overrides) { {args: [:baz, :qux]} }
@@ -109,6 +117,14 @@ def to_block
         end
       end
 
+      context "when `overrides[:kwargs]` is NOT passed" do
+        let(:overrides) { {} }
+
+        it "defaults to empty hash`" do
+          expect(instance.copy(overrides: overrides).kwargs).to eq(constructor_params[:kwargs])
+        end
+      end
+
       context "when `overrides[:kwargs]` is passed" do
         let(:overrides) { {kwargs: {foo: 3, bar: 4}} }
 
@@ -125,6 +141,16 @@ def to_block
         end
       end
 
+      context "when `overrides` is passed" do
+        let(:overrides) { {block: proc { :bar }} }
+
+        it "does NOT mutate `overrides`" do
+          overrides.freeze
+
+          expect { instance.copy(overrides: overrides) }.not_to raise_error(FrozenError)
+        end
+      end
+
       context "when `to_args` is NOT implemented" do
         let(:klass) do
           Class.new(base_class) do