Test terraform state API using Unicorn::TeeInput

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/215391

spec/requests/api/terraform/state_spec.rb

@@ -78,6 +78,14 @@ describe API::Terraform::State do
 
           expect(response).to have_gitlab_http_status(:ok)
         end
+
+        context 'on Unicorn', :unicorn do
+          it 'updates the state' do
+            expect { request }.to change { Terraform::State.count }.by(0)
+
+            expect(response).to have_gitlab_http_status(:ok)
+          end
+        end
       end
 
       context 'without body' do
@@ -112,6 +120,14 @@ describe API::Terraform::State do
 
           expect(response).to have_gitlab_http_status(:ok)
         end
+
+        context 'on Unicorn', :unicorn do
+          it 'creates a new state' do
+            expect { request }.to change { Terraform::State.count }.by(1)
+
+            expect(response).to have_gitlab_http_status(:ok)
+          end
+        end
       end
 
       context 'without body' do

spec/support/unicorn.rb

+# frozen_string_literal: true
+
+REQUEST_CLASSES = [
+  ::Grape::Request,
+  ::Rack::Request
+].freeze
+
+def request_body_class
+  return ::Unicorn::TeeInput if defined?(::Unicorn)
+
+  Class.new(StringIO) do
+    def string
+      raise NotImplementedError, '#string is only valid under Puma which uses StringIO, use #read instead'
+    end
+  end
+end
+
+RSpec.configure do |config|
+  config.before(:each, :unicorn) do
+    REQUEST_CLASSES.each do |request_class|
+      allow_any_instance_of(request_class)
+        .to receive(:body).and_wrap_original do |m, *args|
+          request_body_class.new(m.call(*args).read)
+        end
+    end
+  end
+end