Warn rspec testers when they expect_inertia but render inertia: is never called

Author: bknoles

lib/inertia_rails/rspec.rb

@@ -35,6 +35,9 @@ module Helpers
       def inertia
         raise 'Inertia test helpers aren\'t set up! Make sure you add inertia: true to describe blocks using inertia tests.' unless inertia_tests_setup?
 
+        if @_inertia_render_wrapper.nil? && !::RSpec.configuration.inertia[:skip_missing_renderer_warnings]
+          warn 'WARNING: the test never created an Inertia renderer. Maybe the code wasn\'t able to reach a `render inertia:` call? If this was intended, or you don\'t want to see this message, set ::RSpec.configuration.inertia[:skip_missing_renderer_warnings] = true'
+        end
         @_inertia_render_wrapper
       end
 
@@ -57,6 +60,9 @@ def inertia_tests_setup?
 
 RSpec.configure do |config|
   config.include ::InertiaRails::RSpec::Helpers
+  config.add_setting :inertia, default: {
+    skip_missing_renderer_warnings: false
+  }
 
   config.before(:each, inertia: true) do
     new_renderer = InertiaRails::Renderer.method(:new)

spec/inertia/rspec_helper_spec.rb

@@ -1,5 +1,17 @@
 require_relative '../../lib/inertia_rails/rspec'
 
+class FakeStdErr
+  attr_accessor :messages
+
+  def initialize
+    @messages = []
+  end
+
+  def write(msg)
+    @messages << msg
+  end
+end
+
 RSpec.describe InertiaRails::RSpec, type: :request do
   describe 'correctly set up inertia tests with inertia: true', inertia: true do
     context 'with props' do
@@ -61,5 +73,41 @@
     it 'does not complain about test helpers' do
       expect { expect_inertia }.not_to raise_error
     end
+
+    # h/t for this technique:
+    # https://blog.arkency.com/testing-deprecations-warnings-with-rspec/
+    it 'warns that the renderer was never created' do
+      begin
+        original_stderr = $stderr
+        fake_std_err    = FakeStdErr.new
+        $stderr         = fake_std_err
+        expect_inertia
+        warn_message = 'WARNING: the test never created an Inertia renderer. Maybe the code wasn\'t able to reach a `render inertia:` call? If this was intended, or you don\'t want to see this message, set ::RSpec.configuration.inertia[:skip_missing_renderer_warnings] = true'
+        expect(fake_std_err.messages[0].chomp).to(eq(warn_message))
+      ensure
+        $std_err = original_stderr
+      end
+    end
+
+    context 'with the :skip_missing_renderer_warnings setting set to true' do
+      before {
+        @original = ::RSpec.configuration.inertia[:skip_missing_renderer_warnings]
+        ::RSpec.configuration.inertia[:skip_missing_renderer_warnings] = true
+      }
+      after {
+        ::RSpec.configuration.inertia[:skip_missing_renderer_warnings] = @original
+      }
+      it 'skips the warning' do
+        begin
+          original_stderr = $stderr
+          fake_std_err    = FakeStdErr.new
+          $stderr         = fake_std_err
+          expect_inertia
+          expect(fake_std_err.messages).to be_empty
+        ensure
+          $std_err = original_stderr
+        end
+      end
+    end
   end
 end