Create renderer

lib/kangaru/renderer.rb

@@ -0,0 +1,24 @@
+module Kangaru
+  class Renderer
+    attr_reader :command
+
+    def initialize(command)
+      @command = command
+    end
+
+    def render(binding)
+      return unless view_file.exist?
+
+      puts ERB.new(view_file.read).result(binding)
+    end
+
+    private
+
+    def view_file
+      Kangaru.application.view_file(
+        controller: command.controller,
+        action: command.action.to_s
+      )
+    end
+  end
+end

sig/kangaru/renderer.rbs

@@ -0,0 +1,13 @@
+module Kangaru
+  class Renderer
+    attr_reader command: Command
+
+    def initialize: (Command) -> void
+
+    def render: (Binding) -> void
+
+    private
+
+    def view_file: -> Pathname
+  end
+end

spec/kangaru/renderer_spec.rb

@@ -0,0 +1,68 @@
+RSpec.describe Kangaru::Renderer do
+  subject(:renderer) { described_class.new(command) }
+
+  let(:command)     { instance_spy(Kangaru::Command) }
+  let(:application) { instance_spy(Kangaru::Application, view_file:) }
+
+  let(:view_file) do
+    instance_spy(Pathname, read: view_file_contents, exist?: view_file_exists?)
+  end
+
+  let(:view_file_contents) do
+    <<~ERB
+      Your name is <%= @name %>, you are <%= @age %> years old.
+    ERB
+  end
+
+  before do
+    allow(Kangaru).to receive(:application).and_return(application)
+  end
+
+  describe "#render" do
+    subject(:render) { renderer.render(binding) }
+
+    context "when view file does not exist" do
+      let(:view_file_exists?) { false }
+
+      it "does not output any text" do
+        expect { render }.not_to output.to_stdout
+      end
+    end
+
+    context "when view file exists" do
+      let(:view_file_exists?) { true }
+
+      context "when instance variables do not exist in binding" do
+        let(:expected_output) do
+          <<~STRING
+            Your name is , you are  years old.
+          STRING
+        end
+
+        it "outputs the view file contents with nil interpolated" do
+          expect { render }.to output(expected_output).to_stdout
+        end
+      end
+
+      context "when instance variables exist in binding" do
+        around do |spec|
+          instance_variable_set(:@name, "Foo Bar")
+          instance_variable_set(:@age, 30)
+          spec.run
+          remove_instance_variable(:@name)
+          remove_instance_variable(:@age)
+        end
+
+        let(:expected_output) do
+          <<~STRING
+            Your name is Foo Bar, you are 30 years old.
+          STRING
+        end
+
+        it "outputs the interpolated view file contents" do
+          expect { render }.to output(expected_output).to_stdout
+        end
+      end
+    end
+  end
+end