golib/prometheus/TESTING.md

Testing Guide

Comprehensive testing documentation for the prometheus package, covering test execution, race detection, benchmarks, and quality assurance.

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Table of Contents

• Overview
• Quick Start
• Test Framework
• Running Tests
• Test Coverage
• Thread Safety
• Test Organization
• Writing Tests
• Best Practices
• Troubleshooting
• CI Integration

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Overview

The prometheus package uses Ginkgo v2 (BDD testing framework) and Gomega (matcher library) for comprehensive testing with expressive assertions.

Test Suite Summary

• Total Specs: 426 across 5 packages
• Overall Coverage: 91.6%
• Race Detection: ✅ Zero data races
• Execution Time: ~1.4s (without race), ~7.8s (with race)

Package Breakdown

Package	Specs	Coverage	Duration	Focus
prometheus	137	90.9%	1.38s	Main interface, middleware, routes
bloom	24	94.7%	0.13s	Bloom filter operations
metrics	179	95.5%	0.03s	Metric types, collection, registration
pool	74	72.5%	0.02s	Pool management, concurrency
types	36	100%	0.00s	Type definitions, validation
webmetrics	0	0.0%	-	Simple constructors (no tests needed)

Coverage Areas

• Prometheus interface and middleware
• Metric management (add, delete, list, get, clear)
• Metric collection with Gin context
• Path exclusion and filtering
• Gin integration (routes, middleware, context)
• All metric types (Counter, Gauge, Histogram, Summary)
• Metric pool operations (add, get, del, walk, clear)
• Bloom filter collection and concurrent access
• Thread safety and concurrent operations
• Error handling and edge cases

---

Quick Start

# Install Ginkgo CLI (optional)
go install github.com/onsi/ginkgo/v2/ginkgo@latest

# Run all tests
go test ./...

# With coverage
go test -cover ./...

# With race detection (recommended)
CGO_ENABLED=1 go test -race ./...

# Using Ginkgo CLI
ginkgo -cover -race

Expected Output

ok  	github.com/nabbar/golib/prometheus	        1.385s	coverage: 90.9% of statements
ok  	github.com/nabbar/golib/prometheus/bloom	0.125s	coverage: 94.7% of statements
ok  	github.com/nabbar/golib/prometheus/metrics	0.044s	coverage: 95.5% of statements
ok  	github.com/nabbar/golib/prometheus/pool	    0.026s	coverage: 72.5% of statements
ok  	github.com/nabbar/golib/prometheus/types	0.012s	coverage: 100.0% of statements
?   	github.com/nabbar/golib/prometheus/webmetrics	[no test files]

---

Test Framework

Ginkgo v2 - BDD testing framework (docs)

• Hierarchical test organization (Describe, Context, It)
• Setup/teardown hooks (BeforeEach, AfterEach, BeforeSuite, AfterSuite)
• Parallel execution support
• Rich CLI with filtering and focus

Gomega - Matcher library (docs)

• Readable assertion syntax
• Extensive built-in matchers (Equal, HaveOccurred, ContainSubstring, etc.)
• Detailed failure messages with context
• Custom matcher support

Why Ginkgo/Gomega?

• Better test organization than standard Go testing
• More readable assertions than if err != nil
• Rich failure reporting for debugging
• Industry standard for Go BDD testing

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Running Tests

Basic Commands

# Standard test run
go test ./...

# Verbose output
go test -v ./...

# With coverage
go test -cover ./...

# Generate HTML coverage report
go test -coverprofile=coverage.out ./...
go tool cover -html=coverage.out -o coverage.html

# View function-level coverage
go test -coverprofile=coverage.out ./...
go tool cover -func=coverage.out

Ginkgo CLI Options

# Run all tests
ginkgo

# Specific subpackage
ginkgo ./metrics
ginkgo ./pool
ginkgo ./types

# Specific test file
ginkgo --focus-file=prometheus_basic_test.go

# Pattern matching
ginkgo --focus="should handle concurrent"
ginkgo --focus="Metric Management"

# Parallel execution (faster)
ginkgo -p

# JUnit report for CI
ginkgo --junit-report=results.xml

# Verbose output
ginkgo -v

# Fail fast (stop on first failure)
ginkgo --fail-fast

Race Detection

Critical for concurrent operations testing

# Enable race detector (requires CGO)
CGO_ENABLED=1 go test -race ./...

# With Ginkgo
CGO_ENABLED=1 ginkgo -race

# Specific subpackage
CGO_ENABLED=1 go test -race ./pool

What Race Detector Validates:

• Atomic operations (atomic.Int32, atomic.Bool)
• Mutex protection (sync.Mutex, sync.RWMutex)
• Value synchronization (libatm.Value)
• Goroutine synchronization (sync.WaitGroup)
• Concurrent metric collection

Expected Output:

# ✅ Success (no races)
ok  	github.com/nabbar/golib/prometheus	2.583s

# ❌ Race detected (needs fixing)
WARNING: DATA RACE
Read at 0x00c000123456 by goroutine 42:
  github.com/nabbar/golib/prometheus.(*prom).GetMetric()
      /path/to/file.go:123 +0x45

Current Status: ✅ Zero data races detected across all tests

Performance & Profiling

# Benchmarks (if available)
go test -bench=. -benchmem ./...

# Memory profiling
go test -memprofile=mem.out ./...
go tool pprof mem.out

# CPU profiling
go test -cpuprofile=cpu.out ./...
go tool pprof cpu.out

# Trace execution
go test -trace=trace.out ./...
go tool trace trace.out

Performance Expectations

Test Type	Duration	Notes
Root package	~1.4s	Without race
All subpackages	~3s	Without race
With -race	~8s	2-3x slower (normal)
Individual spec	<100ms	Most tests
Integration tests	200-500ms	With HTTP server

---

Test Coverage

Target: ≥80% statement coverage (Currently: ~95%)

Coverage by Category

Category	Files	Description
Basic Operations	prometheus_basic_test.go	Constructor, slow time, duration, thread safety
Metric Management	prometheus_metrics_test.go	Add, get, delete, list metrics
Collection	prometheus_collect_test.go	Metric collection, Gin context, concurrent collection
Exclusion	prometheus_exclude_test.go	Path exclusion, patterns, edge cases
Gin Integration	prometheus_gin_test.go	Middleware, routes, handlers, context
Integration	prometheus_integration_test.go	Complete workflows, error handling
Metrics	metrics/*_test.go	Metric types, collectors, operations
Pool	pool/*_test.go	Pool operations, concurrency, edge cases
Types	types/*_test.go	Type registration, validation, constants
Bloom	bloom/*_test.go	Bloom filter operations, accuracy

View Coverage Details

# Generate coverage report
go test -coverprofile=coverage.out ./...

# View summary
go tool cover -func=coverage.out | tail -1

# View by package
go tool cover -func=coverage.out | grep -E "prometheus/(metrics|pool|types)"

# Generate HTML report
go tool cover -html=coverage.out -o coverage.html
# Open coverage.html in browser to see line-by-line coverage

# Find uncovered lines
go tool cover -func=coverage.out | grep -v "100.0%"

Test Structure

Tests follow Ginkgo's hierarchical BDD structure:

var _ = Describe("Prometheus Component", func() {
    var (
        prm prometheus.Prometheus
    )

    BeforeEach(func() {
        // Per-test setup
        prm = newPrometheus()
    })
    
    AfterEach(func() {
        // Per-test cleanup
        cleanupPrometheus(prm)
    })
    
    Context("When performing operation", func() {
        It("should behave correctly", func() {
            // Arrange
            metric := createCounterMetric("test_metric")
            
            // Act
            err := prm.AddMetric(true, metric)
            
            // Assert
            Expect(err).ToNot(HaveOccurred())
            Expect(prm.GetMetric("test_metric")).ToNot(BeNil())
        })
    })
})

---

Thread Safety

Thread safety is critical for the prometheus package's concurrent operations.

Concurrency Primitives

// Atomic scalar values
atomic.Int32           // For slow time threshold
atomic.Bool            // For state flags

// Thread-safe complex values
libatm.Value[[]string]   // For excluded paths
libatm.Value[[]float64]  // For duration buckets

// Synchronization
sync.Mutex             // For buffer protection
sync.WaitGroup         // For goroutine lifecycle

Verified Components

Component	Mechanism	Test File	Status
prom.SetSlowTime/GetSlowTime	atomic.Int32	prometheus_basic_test.go	✅ Race-free
prom.SetDuration/GetDuration	libatm.Value	prometheus_basic_test.go	✅ Race-free
prom.ExcludePath	libatm.Value	prometheus_exclude_test.go	✅ Race-free
pool.Add/Get/Del	sync.Map	pool/*_test.go	✅ Race-free
Metric.Collect	Semaphore	prometheus_collect_test.go	✅ Race-free

Testing Concurrent Operations

# Run tests with race detector
CGO_ENABLED=1 go test -race ./...

# Focus on concurrent tests
CGO_ENABLED=1 go test -race -v -run "Concurrent" ./...
CGO_ENABLED=1 go test -race -v -run "Thread" ./...

# Stress test (run multiple times)
for i in {1..10}; do 
    echo "Run $i"
    CGO_ENABLED=1 go test -race ./... || break
done

Concurrent Test Examples

It("should handle concurrent metric additions", func() {
    var wg sync.WaitGroup
    
    for i := 0; i < 100; i++ {
        wg.Add(1)
        go func(id int) {
            defer wg.Done()
            name := fmt.Sprintf("metric_%d", id)
            m := createCounterMetric(name)
            defer cleanupMetric(m)
            
            err := p.AddMetric(true, m)
            Expect(err).ToNot(HaveOccurred())
        }(i)
    }
    
    wg.Wait()
})

Result: Zero data races across all test runs

---

Test Organization

Root Package Tests

File	Purpose	Specs	Key Tests
prometheus_suite_test.go	Suite initialization	1	Helper functions, cleanup
prometheus_basic_test.go	Basic operations	18	Constructor, config, thread safety
prometheus_metrics_test.go	Metric management	30	Add, get, delete, list, concurrent
prometheus_collect_test.go	Collection	24	Collect, Gin context, concurrency
prometheus_exclude_test.go	Path exclusion	18	Patterns, edge cases, concurrent
prometheus_gin_test.go	Gin integration	26	Middleware, routes, handlers
prometheus_integration_test.go	Integration	21	Complete workflows, errors

Subpackage Tests

metrics/

• metrics_suite_test.go - Suite initialization
• metrics_basic_test.go - Metric creation and configuration
• metrics_operations_test.go - Inc, Dec, Set, Observe operations
• Coverage: 95.3%

pool/

• pool_suite_test.go - Suite initialization
• pool_basic_test.go - Add, Get, Del, List operations
• pool_walk_test.go - Walk functionality
• pool_edge_cases_test.go - Edge cases and concurrency
• Coverage: 90.6%

types/

• types_suite_test.go - Suite initialization
• types_registration_test.go - Type registration and validation
• types_values_test.go - Type constants and comparisons
• Coverage: 100%

bloom/

• bloom_suite_test.go - Suite initialization
• bloom_basic_test.go - Add, Test, Count operations
• Coverage: 94.7%

---

Writing Tests

Guidelines

1. Use Descriptive Names

// ✅ Good: Clear, specific description
It("should successfully add metric with valid configuration", func() {
    // Test implementation
})

// ❌ Bad: Vague description
It("should work", func() {
    // Test implementation
})

2. Follow AAA Pattern (Arrange, Act, Assert)

It("should increment counter metric", func() {
    // Arrange
    counter := createCounterMetric("test_counter")
    defer cleanupMetric(counter)
    labels := map[string]string{"method": "GET"}
    
    // Act
    counter.Inc(labels)
    
    // Assert
    // Verify counter was incremented (via collection or export)
    Expect(counter).ToNot(BeNil())
})

3. Use Appropriate Matchers

// Error checking
Expect(err).ToNot(HaveOccurred())
Expect(err).To(HaveOccurred())
Expect(err.Error()).To(ContainSubstring("expected text"))

// Value checking
Expect(value).To(Equal(expected))
Expect(list).To(ContainElement(item))
Expect(number).To(BeNumerically(">", 0))
Expect(result).ToNot(BeNil())

// Type checking
Expect(obj).To(BeAssignableToTypeOf(&prometheus.Prom{}))

4. Always Cleanup Resources

It("should cleanup metrics after test", func() {
    metric := createCounterMetric("temp_metric")
    defer cleanupMetric(metric)  // Always cleanup
    
    err := p.AddMetric(true, metric)
    Expect(err).ToNot(HaveOccurred())
})

5. Test Edge Cases

• Empty inputs
• Nil values
• Large data sets
• Invalid configurations
• Concurrent operations
• Error conditions

6. Avoid External Dependencies

• No remote API calls
• No external databases
• Use in-memory test servers
• Mock external dependencies

Test Template

var _ = Describe("Prometheus New Feature", func() {
    var (
        prm    prometheus.Prometheus
        metric prmmet.Metric
    )

    BeforeEach(func() {
        prm = newPrometheus()
    })

    AfterEach(func() {
        if metric != nil {
            cleanupMetric(metric)
        }
    })

    Context("When using new feature", func() {
        It("should perform expected behavior", func() {
            // Arrange
            metric = createCounterMetric("test_metric")
            
            // Act
            err := prm.AddMetric(true, metric)
            
            // Assert
            Expect(err).ToNot(HaveOccurred())
            retrieved := prm.GetMetric("test_metric")
            Expect(retrieved).ToNot(BeNil())
            Expect(retrieved.GetName()).To(Equal("test_metric"))
        })

        It("should handle error case", func() {
            // Test error condition
            err := prm.AddMetric(true, nil)
            Expect(err).To(HaveOccurred())
        })
    })
})

Helper Functions

The test suite provides helper functions for common operations:

// Create Prometheus instance
prm := newPrometheus()

// Create metrics
counter := createCounterMetric("metric_name")
gauge := createGaugeMetric("metric_name")
histogram := createHistogramMetric("metric_name")
summary := createSummaryMetric("metric_name")

// Unique metric names (avoids conflicts)
name := uniqueMetricName("prefix")

// Create context
ctx := createContextFunc()()

// Cleanup
cleanupMetric(metric)
cleanupPrometheus(prm)

---

Best Practices

Test Independence

• ✅ Each test should be independent
• ✅ Use BeforeEach/AfterEach for setup/cleanup
• ✅ Avoid global mutable state
• ✅ Create test data on-demand
• ❌ Don't rely on test execution order

Test Data

// ✅ Good: Use helper functions
name := uniqueMetricName("test")
metric := createCounterMetric(name)

// ✅ Good: Explicit cleanup
defer cleanupMetric(metric)

// ❌ Bad: Hardcoded names (can cause conflicts)
metric := createCounterMetric("test_metric")

Assertions

// ✅ Good: Use specific matchers
Expect(err).ToNot(HaveOccurred())
Expect(value).To(Equal(expected))
Expect(list).To(HaveLen(3))

// ❌ Bad: Generic boolean checks
Expect(value == expected).To(BeTrue())
Expect(len(list) == 3).To(BeTrue())

Concurrency Testing

It("should handle concurrent operations", func() {
    var wg sync.WaitGroup
    
    for i := 0; i < 10; i++ {
        wg.Add(1)
        go func(id int) {
            defer wg.Done()
            // Perform operation
            name := uniqueMetricName("concurrent")
            m := createCounterMetric(name)
            defer cleanupMetric(m)
            
            err := p.AddMetric(true, m)
            Expect(err).ToNot(HaveOccurred())
        }(i)
    }
    
    wg.Wait()
})

Always run concurrent tests with -race

Performance

• Keep tests fast (<100ms per spec)
• Use parallel execution when safe
• Avoid unnecessary sleeps
• Use Eventually for async operations

// ✅ Good: Use Eventually for async
Eventually(func() bool {
    return condition()
}).Should(BeTrue())

// ❌ Bad: Sleep and hope
time.Sleep(100 * time.Millisecond)
Expect(condition()).To(BeTrue())

Error Handling

// ✅ Good: Always check errors
result, err := operation()
Expect(err).ToNot(HaveOccurred())
defer result.Close()

// ❌ Bad: Ignore errors
result, _ := operation()

Test Organization

• Group related tests in Context blocks
• Use descriptive Describe and Context names
• Keep It blocks focused (one behavior per test)
• Use BeforeEach for common setup

---

Troubleshooting

Import Cycles

# Error: import cycle
package github.com/nabbar/golib/prometheus
    imports github.com/nabbar/golib/prometheus/metrics
    imports github.com/nabbar/golib/prometheus

# Solution: Use package_test naming
package prometheus_test  // Not package prometheus

Stale Coverage

# Clean test cache
go clean -testcache

# Re-run tests
go test -coverprofile=coverage.out ./...

Race Conditions

# Debug races with verbose output
CGO_ENABLED=1 go test -race -v ./... 2>&1 | tee race-log.txt

# Find race warnings
grep -A 20 "WARNING: DATA RACE" race-log.txt

Common Race Fixes:

// ❌ Bad: Direct field access
if m.field == value {  // Race condition!

// ✅ Good: Use atomic or mutex
if m.getField() == value {  // Protected access

Test Timeouts

# Increase timeout
go test -timeout=5m ./...

# With Ginkgo
ginkgo --timeout=5m

Check for:

• Goroutine leaks (missing wg.Done())
• Unclosed resources
• Infinite loops
• Mutex deadlocks

Debugging Specific Tests

# Run single test
ginkgo --focus="should add metric"

# Run specific file
ginkgo --focus-file=prometheus_basic_test.go

# Verbose output
ginkgo -v --trace

# Skip tests
ginkgo --skip="slow integration"

Use GinkgoWriter for debug output:

fmt.Fprintf(GinkgoWriter, "Debug: value = %v\n", value)

CGO Not Available

# Install build tools
# Ubuntu/Debian
sudo apt-get install build-essential

# macOS
xcode-select --install

# Verify
export CGO_ENABLED=1
go test -race ./...

Parallel Test Failures

• Check for shared resources
• Verify proper synchronization
• Use unique names for test data
• Avoid global state

Memory Leaks

# Check for memory leaks
go test -memprofile=mem.out ./...
go tool pprof -alloc_space mem.out

---

CI Integration

GitHub Actions Example

name: Tests
on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        go-version: ['1.18', '1.19', '1.20', '1.21']
    
    steps:
      - uses: actions/checkout@v3
      
      - uses: actions/setup-go@v4
        with:
          go-version: ${{ matrix.go-version }}
      
      - name: Install dependencies
        run: go mod download
      
      - name: Run tests
        run: go test -v ./...
      
      - name: Race detection
        run: CGO_ENABLED=1 go test -race -timeout=10m ./...
      
      - name: Coverage
        run: |
          go test -coverprofile=coverage.out ./...
          go tool cover -func=coverage.out
      
      - name: Upload coverage
        uses: codecov/codecov-action@v3
        with:
          file: ./coverage.out
          fail_ci_if_error: true

GitLab CI Example

test:
  image: golang:1.21
  script:
    - go test -v ./...
    - CGO_ENABLED=1 go test -race ./...
    - go test -coverprofile=coverage.out ./...
  coverage: '/coverage: \d+.\d+% of statements/'
  artifacts:
    reports:
      coverage_report:
        coverage_format: cobertura
        path: coverage.xml

Pre-commit Hook

#!/bin/bash
# .git/hooks/pre-commit

echo "Running tests..."
go test ./... || exit 1

echo "Running race detector..."
CGO_ENABLED=1 go test -race ./... || exit 1

echo "Checking coverage..."
go test -coverprofile=coverage.out ./...
COVERAGE=$(go tool cover -func=coverage.out | grep total | awk '{print $3}' | sed 's/%//')
if (( $(echo "$COVERAGE < 80" | bc -l) )); then
    echo "Coverage is below 80%: $COVERAGE%"
    exit 1
fi

echo "All checks passed!"

Make it executable:

chmod +x .git/hooks/pre-commit

---

Quality Checklist

Before merging code:

• All tests pass: go test ./...
• Race detection clean: CGO_ENABLED=1 go test -race ./...
• Coverage maintained: ≥80% (current: ~95%)
• New features have tests
• Error cases tested
• Thread safety validated
• Edge cases covered
• Test duration reasonable (<10s)
• No test flakiness
• GoDoc comments updated
• README.md updated if needed

---

Resources

Testing Frameworks

• Ginkgo Documentation
• Gomega Matchers
• Go Testing
• Go Coverage

Concurrency

• Go Race Detector
• Go Memory Model
• sync Package
• atomic Package

Performance

• Go Profiling
• Benchmarking
• Trace Execution

Prometheus

• Prometheus Best Practices
• Prometheus Client
• Writing Exporters

---

AI Transparency Notice

In accordance with Article 50.4 of the EU AI Act, AI assistance has been used for testing, documentation, and bug fixing under human supervision.

---

Version: Go 1.18+ on Linux, macOS, Windows
Maintained By: Prometheus Package Contributors