Add basic test for AppFileRun component

Author: rossta

spec/views/components/code_block/app_file_run_spec.rb

@@ -0,0 +1,23 @@
+require "rails_helper"
+
+RSpec.describe CodeBlock::AppFileRun, type: :view do
+  def render_page(*, **)
+    Capybara.string(render(*, **))
+  end
+
+  before do
+    allow(view).to receive(:headers).and_return({"Content-Type" => "text/html"})
+  end
+
+  it "renders contents of file" do
+    page = render_page(CodeBlock::AppFileRun.new("spec/fixtures/code_block/app_file/example.rb"))
+    expect(page).to have_content(<<~RUBY.strip)
+      class FixturesCodeBlockAppFileExample
+        def add(m, n)
+          m + n
+        end
+      end
+    RUBY
+    expect(page).to have_content("spec/fixtures/code_block/app_file/example.rb")
+  end
+end