kubernetes/vendor/github.com/prometheus/client_golang/prometheus/testutil/testutil.go

// ToFloat64 collects all Metrics from the provided Collector. It expects that
// this results in exactly one Metric being collected, which must be a Gauge,
// Counter, or Untyped. In all other cases, ToFloat64 panics. ToFloat64 returns
// the value of the collected Metric.
//
// The Collector provided is typically a simple instance of Gauge or Counter, or
// – less commonly – a GaugeVec or CounterVec with exactly one element. But any
// Collector fulfilling the prerequisites described above will do.
//
// Use this function with caution. It is computationally very expensive and thus
// not suited at all to read values from Metrics in regular code. This is really
// only for testing purposes, and even for testing, other approaches are often
// more appropriate (see this package's documentation).
//
// A clear anti-pattern would be to use a metric type from the prometheus
// package to track values that are also needed for something else than the
// exposition of Prometheus metrics. For example, you would like to track the
// number of items in a queue because your code should reject queuing further
// items if a certain limit is reached. It is tempting to track the number of
// items in a prometheus.Gauge, as it is then easily available as a metric for
// exposition, too. However, then you would need to call ToFloat64 in your
// regular code, potentially quite often. The recommended way is to track the
// number of items conventionally (in the way you would have done it without
// considering Prometheus metrics) and then expose the number with a
// prometheus.GaugeFunc.
func ToFloat64(c prometheus.Collector) float64 { … }

// CollectAndCount registers the provided Collector with a newly created
// pedantic Registry. It then calls GatherAndCount with that Registry and with
// the provided metricNames. In the unlikely case that the registration or the
// gathering fails, this function panics. (This is inconsistent with the other
// CollectAnd… functions in this package and has historical reasons. Changing
// the function signature would be a breaking change and will therefore only
// happen with the next major version bump.)
func CollectAndCount(c prometheus.Collector, metricNames ...string) int { … }

// GatherAndCount gathers all metrics from the provided Gatherer and counts
// them. It returns the number of metric children in all gathered metric
// families together. If any metricNames are provided, only metrics with those
// names are counted.
func GatherAndCount(g prometheus.Gatherer, metricNames ...string) (int, error) { … }

// ScrapeAndCompare calls a remote exporter's endpoint which is expected to return some metrics in
// plain text format. Then it compares it with the results that the `expected` would return.
// If the `metricNames` is not empty it would filter the comparison only to the given metric names.
func ScrapeAndCompare(url string, expected io.Reader, metricNames ...string) error { … }

// CollectAndCompare registers the provided Collector with a newly created
// pedantic Registry. It then calls GatherAndCompare with that Registry and with
// the provided metricNames.
func CollectAndCompare(c prometheus.Collector, expected io.Reader, metricNames ...string) error { … }

// GatherAndCompare gathers all metrics from the provided Gatherer and compares
// it to an expected output read from the provided Reader in the Prometheus text
// exposition format. If any metricNames are provided, only metrics with those
// names are compared.
func GatherAndCompare(g prometheus.Gatherer, expected io.Reader, metricNames ...string) error { … }

// TransactionalGatherAndCompare gathers all metrics from the provided Gatherer and compares
// it to an expected output read from the provided Reader in the Prometheus text
// exposition format. If any metricNames are provided, only metrics with those
// names are compared.
func TransactionalGatherAndCompare(g prometheus.TransactionalGatherer, expected io.Reader, metricNames ...string) error { … }

// convertReaderToMetricFamily would read from a io.Reader object and convert it to a slice of
// dto.MetricFamily.
func convertReaderToMetricFamily(reader io.Reader) ([]*dto.MetricFamily, error) { … }

// compareMetricFamilies would compare 2 slices of metric families, and optionally filters both of
// them to the `metricNames` provided.
func compareMetricFamilies(got, expected []*dto.MetricFamily, metricNames ...string) error { … }

// compare encodes both provided slices of metric families into the text format,
// compares their string message, and returns an error if they do not match.
// The error contains the encoded text of both the desired and the actual
// result.
func compare(got, want []*dto.MetricFamily) error { … }

// diff returns a diff of both values as long as both are of the same type and
// are a struct, map, slice, array or string. Otherwise it returns an empty string.
func diff(expected, actual interface{ … }

// typeAndKind returns the type and kind of the given interface{}
func typeAndKind(v interface{ … }

func filterMetrics(metrics []*dto.MetricFamily, names []string) []*dto.MetricFamily { … }