Unit test using golang prometheus testutil

Question

We can assert that a metric is registered and collected using testutil.CollectAndCount and testutil.CollectAndCompare etc. But is there a way to collect the metrics by metric name and the labels if it's CounterVec.

for reference https://godoc.org/github.com/prometheus/client_golang/prometheus/testutil

Hi, not sure if I understood your question entirely: do you want to test the output of a CounterVec as text or are you trying to assert that the value is correct? — Francesco Gualazzi
– Francesco Gualazzi, Commented Jan 15, 2021 at 10:01

katexochen · Accepted Answer · 2021-06-26 08:30:51Z

15

As I understood your question, you want to test the value of a metric with a specific label from a metrics collection like CounterVec.

You can do so by using the ToFloat64 function in combination with the WithLabelsValue function, as in the following example:

import (
    "testing"

    "github.com/prometheus/client_golang/prometheus"
    "github.com/prometheus/client_golang/prometheus/testutil"
    "github.com/stretchr/testify/assert"
)

func TestVecMetricT(t *testing.T) {
    assert := assert.New(t)

    var C = prometheus.NewCounterVec(prometheus.CounterOpts{
        Name: "C",
        Help: "Help",
    }, []string{"subname"},
    )

    prometheus.MustRegister(C)

    C.WithLabelValues("firstLabel").Inc()
    C.WithLabelValues("secondLabel").Inc()
    C.WithLabelValues("thirdLabel").Inc()
    C.WithLabelValues("thirdLabel").Inc()

    // collected three metrics
    assert.Equal(3, testutil.CollectAndCount(C))
    // check the expected values using the ToFloat64 function
    assert.Equal(float64(1), testutil.ToFloat64(C.WithLabelValues("firstLabel")))
    assert.Equal(float64(1), testutil.ToFloat64(C.WithLabelValues("secondLabel")))
    assert.Equal(float64(2), testutil.ToFloat64(C.WithLabelValues("thirdLabel")))
}

Correct me if I'm wrong, but I don't think there a way to use the testutil package to get a slice of label values from a metric collection like CounterVec.

answered Jun 26, 2021 at 8:30

katexochen

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1 Comment

Alexis Wilke Over a year ago

This is strange. It looks like you have to use a vector to have access to the ToFloat64() functionality. At first I just had a Gauge instead of a GaugeVec and I could not see how to get the value out of it!?

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