prometheus_testing

Simple and naive package for easier testing of prometheus metrics

Motivation

While I was working with prometheus I wanted to be sure that my counters were being called when I was expecting them to and also that they were being upped the correct number of times as well as with the proper labels (when it applies).

prometheus provides certain testing helpers but none were what I was expecting; so I decided to create a simple set of helpers to easily verify counters modifications with the desired values.

Usage

// Let's import with a `.` to make the functions available in the current context
// If you don't want to do this make sure to prepend the functions with `promtest`
import (
   . "github.com/esttorhe/prometheus_testing"
)

func TestClass_MethodUpsPrometheusCounter_WhenConditionsAreMet(t *testing.T) {
   // Create if needed the counter we are interested in checking
   // otherwise just jump over to the registration part
	counterName := "Counter"
	counter := prometheus.NewCounterVec(prometheus.CounterOpts{
		Namespace: "Namespace",
		Subsystem: "Subsystem",
		Name:      "Name",
		Help:      "Help",
   }, []string{"label"})
   
   // Create a new registry just for testing
   // Let's avoid messing with our production registry
   reg := prometheus.NewRegistry()
   reg.MustRegister(counter)
   defer reg.Unregister(counter)

   sut := SubjectUnderTest{}
   sut.Method()
   // Check that the counter was upped in the registry (`reg`)
   // The «current» value after upping should be `1` (as passed in the parameter)
   // Because this is a `CounterVec` we can pass an unlimited ammount of `ExpectationLabelPair`s that
   // will be used to check that everything was upped using the proper labels.
   CheckPrometheusCounterVec(t, reg, counter, 1,
      ExpectationLabelPair{LabelName: "label", LabelValue: rule.Name},
   )
}

The other 2 helper functions should be used exactly like the example above. The other 2 are:

Function	Description
`CheckPrometheusCounterVec`	Helper method that checks that a prometheus counter vec has the expected value for the expected label pairs on the passed in registry
`CheckPrometheusCounterVecNotCalled`	Helper method that checks that a prometheus counter vec doesn't get called with a set of parameters on the passed in registry
`CheckPrometheusCounter`	Helper method that checks that a prometheus counter has the expected value on the passed in registry

Author

Esteban Torres

✉ me+github_prometheus_testing@estebantorr.es

License

prometheus_testing is available under the MIT license. See the LICENSE file for more info.