github.com/prometheus/client_model v0.5.0: go.Counter

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify github.com/prometheus/client_model/go.Counter in pkg:golang/github.com/prometheus/client_model@v0.5.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/prometheus/client_model@v0.5.0
Demonstrate these symbols/APIs:
  - github.com/prometheus/client_model/go.Counter
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:d6451a571d6d60e0720e304c92d72ef0112bb73be7ad420e72f36d67b92350ca","contract":["dto.Counter.GetValue returns 0 for a nil or uninitialized Counter, and returns the configured float64 value when set.","dto.Counter attaches an Exemplar containing label pairs, float64 value, and timestamp, accessible via GetExemplar.","dto.Counter tracks a created timestamp accessible via GetCreatedTimestamp.","dto.Counter.Reset resets the counter value back to 0."],"goal":"verify github.com/prometheus/client_model/go.Counter in pkg:golang/github.com/prometheus/client_model@v0.5.0","kind":"HOW","packages":["pkg:golang/github.com/prometheus/client_model@v0.5.0"],"schemaVersion":1,"symbols":["github.com/prometheus/client_model/go.Counter"]},"contractCommand":["go","test","./..."],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","executionContext":"go","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","runtime":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/prometheus/client_model@v0.5.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/prometheus/client_model@v0.5.0","symbols":["github.com/prometheus/client_model/go.Counter"],"verifierAdapter":"golang@1"}

module example.com/counter

go 1.26.6

require (
	github.com/prometheus/client_model v0.5.0
	google.golang.org/protobuf v1.31.0
)

github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
github.com/prometheus/client_model v0.5.0 h1:VQw1hfvPvk3Uv6Qf29VrPF32JB6rtbgI6cYPYQjL0Qw=
github.com/prometheus/client_model v0.5.0/go.mod h1:dTiFglRmd66nLR9Pv9f0mZi7B7fk5Pm3gvsjB5tr+kI=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
google.golang.org/protobuf v1.31.0 h1:g0LDEJHgrBl9N9r17Ru3sqWhkIx2NB67okBHPwC7hs8=
google.golang.org/protobuf v1.31.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=

package main

import (
	"fmt"

	dto "github.com/prometheus/client_model/go"
	"google.golang.org/protobuf/proto"
	"google.golang.org/protobuf/types/known/timestamppb"
)

func main() {
	now := timestamppb.Now()
	exemplar := &dto.Exemplar{
		Label: []*dto.LabelPair{
			{
				Name:  proto.String("trace_id"),
				Value: proto.String("abc-123"),
			},
		},
		Value:     proto.Float64(1.0),
		Timestamp: now,
	}

	counter := &dto.Counter{
		Value:            proto.Float64(42.0),
		Exemplar:         exemplar,
		CreatedTimestamp: now,
	}

	fmt.Printf("Counter value: %f\n", counter.GetValue())
	if ex := counter.GetExemplar(); ex != nil {
		fmt.Printf("Exemplar value: %f\n", ex.GetValue())
	}
	if ts := counter.GetCreatedTimestamp(); ts != nil {
		fmt.Printf("Created timestamp: %d\n", ts.GetSeconds())
	}

	counter.Reset()
	fmt.Printf("After reset: %f\n", counter.GetValue())
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/prometheus/client_model/go.Counter in pkg:golang/github.com/prometheus/client_model@v0.5.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/prometheus/client_model@v0.5.0"
  ],
  "symbols": [
    "github.com/prometheus/client_model/go.Counter"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

package test

import (
	"testing"

	dto "github.com/prometheus/client_model/go"
	"google.golang.org/protobuf/proto"
	"google.golang.org/protobuf/types/known/timestamppb"
)

func TestCounterGetValue(t *testing.T) {
	// Nil counter returns 0
	var nilCounter *dto.Counter
	if got := nilCounter.GetValue(); got != 0 {
		t.Errorf("nilCounter.GetValue() = %v, want 0", got)
	}

	// Empty counter returns 0
	emptyCounter := &dto.Counter{}
	if got := emptyCounter.GetValue(); got != 0 {
		t.Errorf("emptyCounter.GetValue() = %v, want 0", got)
	}

	// Counter with configured value
	val := 42.5
	counter := &dto.Counter{
		Value: proto.Float64(val),
	}
	if got := counter.GetValue(); got != val {
		t.Errorf("counter.GetValue() = %v, want %v", got, val)
	}
}

func TestCounterExemplar(t *testing.T) {
	labelName := "trace_id"
	labelVal := "abc-123"
	exemplarVal := 1.5
	ts := timestamppb.Now()

	exemplar := &dto.Exemplar{
		Label: []*dto.LabelPair{
			{
				Name:  proto.String(labelName),
				Value: proto.String(labelVal),
			},
		},
		Value:     proto.Float64(exemplarVal),
		Timestamp: ts,
	}

	counter := &dto.Counter{
		Value:    proto.Float64(100.0),
		Exemplar: exemplar,
	}

	got := counter.GetExemplar()
	if got == nil {
		t.Fatal("counter.GetExemplar() returned nil, expected exemplar")
	}
	if got.GetValue() != exemplarVal {
		t.Errorf("exemplar.GetValue() = %v, want %v", got.GetValue(), exemplarVal)
	}
	if len(got.GetLabel()) != 1 || got.GetLabel()[0].GetName() != labelName || got.GetLabel()[0].GetValue() != labelVal {
		t.Errorf("exemplar labels mismatch: got %v", got.GetLabel())
	}
}

func TestCounterCreatedTimestamp(t *testing.T) {
	ts := timestamppb.Now()
	counter := &dto.Counter{
		Value:            proto.Float64(10.0),
		CreatedTimestamp: ts,
	}

	gotTs := counter.GetCreatedTimestamp()
	if gotTs == nil {
		t.Fatal("counter.GetCreatedTimestamp() returned nil, expected timestamp")
	}
	if gotTs.GetSeconds() != ts.GetSeconds() {
		t.Errorf("created timestamp seconds = %v, want %v", gotTs.GetSeconds(), ts.GetSeconds())
	}
}

func TestCounterReset(t *testing.T) {
	counter := &dto.Counter{
		Value: proto.Float64(99.9),
	}
	counter.Reset()
	if got := counter.GetValue(); got != 0 {
		t.Errorf("counter.GetValue() after Reset() = %v, want 0", got)
	}
}