Testing

This guide explains how to write assertions in your test suite to validate metrics are being emitted correctly.

Application Code

In your application code, you should emit metrics, e.g.

require 'metrics/provider'

class MyApplication
	def work
		# ...
	end
	
	Metrics::Provider(self) do
		WORK_METRIC = Metrics.metric('my_application.work.count', :counter, description: 'Work counter')
		
		def work
			WORK_METRIC.emit(1)
			super
		end
	end
end

Test Code

In your test code, you should assert that the metrics are being emitted correctly, e.g.

ENV['METRICS_BACKEND'] ||= 'metrics/backend/test'

require_relative 'app'

describe MyApplication do
	it 'should emit metrics' do
		expect(MyApplication::WORK_METRIC).to receive(:emit).with(1)
		MyApplication.new.work
	end
end