1 files changed, 67 insertions, 0 deletions
diff --git a/spec/initializers/validate_puma_spec.rb b/spec/initializers/validate_puma_spec.rb
new file mode 100644
index 00000000000..9ff0ef2c319
--- /dev/null
+++ b/spec/initializers/validate_puma_spec.rb
@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'validate puma' do
+  include RakeHelpers
+
+  subject do
+    load Rails.root.join('config/initializers/validate_puma.rb')
+  end
+
+  before do
+    stub_const('Puma', double)
+    allow(Gitlab::Runtime).to receive(:puma?).and_return(true)
+    allow(Puma).to receive_message_chain(:cli_config, :options).and_return(workers: workers)
+  end
+
+  context 'for .com' do
+    before do
+      allow(Gitlab).to receive(:com?).and_return(true)
+    end
+
+    context 'when worker count is 0' do
+      let(:workers) { 0 }
+
+      specify { expect { subject }.to raise_error(String) }
+    end
+
+    context 'when worker count is > 0' do
+      let(:workers) { 2 }
+
+      specify { expect { subject }.not_to raise_error }
+    end
+  end
+
+  context 'for other environments' do
+    before do
+      allow(Gitlab).to receive(:com?).and_return(false)
+
+      allow(main_object).to receive(:warn)
+    end
+
+    context 'when worker count is 0' do
+      let(:workers) { 0 }
+
+      specify { expect { subject }.not_to raise_error }
+
+      it 'warns about running Puma in a Single mode' do
+        expect(main_object).to receive(:warn) do |warning|
+          expect(warning).to include('https://gitlab.com/groups/gitlab-org/-/epics/5303')
+        end
+
+        subject
+      end
+    end
+
+    context 'when worker count is > 0' do
+      let(:workers) { 2 }
+
+      specify { expect { subject }.not_to raise_error }
+
+      it 'does not issue a warning' do
+        expect(main_object).not_to receive(:warn)
+      end
+    end
+  end
+end