golib/viper/TESTING.md

Testing Guide

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

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Table of Contents

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

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Overview

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

Test Suite

• Total Specs: 104
• Coverage: 73.3%
• Race Detection: ✅ Zero data races
• Execution Time: ~0.05s (without race), ~1.1s (with race)

Coverage Areas

• Viper instance creation and initialization
• All getter methods (17 types)
• Configuration loading (file, env, remote, default)
• Unmarshalling operations (standard, exact, key-specific)
• Custom decode hooks
• Configuration key unsetting
• Error handling and validation
• Concurrent access patterns

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Quick Start

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

# Run all tests
go test ./...

# Run with coverage
go test -cover ./...

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

# Using Ginkgo CLI
ginkgo -cover -race

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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

Gomega - Matcher library (docs)

• Readable assertion syntax
• Extensive built-in matchers
• Detailed failure messages

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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

Ginkgo CLI Options

# Run all tests
ginkgo

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

# Pattern matching
ginkgo --focus="unmarshall"

# Parallel execution
ginkgo -p

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

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

Validates:

• Atomic operations (atomic.Uint32)
• Thread-safe hook storage
• Concurrent configuration access
• Viper core thread safety

Expected Output:

# ✅ Success
ok  	github.com/nabbar/golib/viper	1.093s

# ❌ Race detected
WARNING: DATA RACE
Read at 0x... by goroutine ...

Status: Zero data races detected

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

Performance Expectations

Test Type	Duration	Notes
Full Suite	~0.05s	Without race
With -race	~1.1s	20x slower (normal)
Individual Spec	<10ms	Most tests
File I/O Tests	10-50ms	Temporary file operations

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Test Coverage

Target: ≥70% statement coverage

Coverage By Category

Category	Files	Description
Creation	viper_test.go	Instance creation, logger initialization
Getters	viper_test.go	All 17 getter methods (bool, string, int, float, time, slices, maps)
Configuration	config_test.go	File loading, env vars, default config, multi-format support
Unmarshalling	unmarshall_test.go	Unmarshal, UnmarshalKey, UnmarshalExact, type conversions
Hooks	hook_test.go	Hook registration, reset, composition, execution
Cleaner	cleaner_test.go	Unset operations, nested keys, preservation
Errors	error_test.go	All 11 error codes, messages, chaining
Concurrency	viper_test.go	Concurrent reads, thread safety

View Coverage

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

# View in terminal
go tool cover -func=coverage.out

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

Coverage Details

Total Coverage:     73.3%

By File:
- viper.go          100.0%  (All getters)
- interface.go      100.0%  (New function)
- model.go          95.0%   (Setters and config)
- config.go         85.0%   (File and default config)
- unmarshall.go     90.0%   (All unmarshal methods)
- hook.go           80.0%   (Hook management)
- cleaner.go        95.0%   (Unset operations)
- errors.go         100.0%  (Error definitions)
- remote.go         0.0%    (Requires ETCD - not tested)
- watch.go          0.0%    (Requires file watching - not tested)

Test Structure

Tests follow Ginkgo's hierarchical BDD structure:

Describe("viper/component", func() {
    BeforeSuite(func() {
        // Global setup
    })
    
    AfterSuite(func() {
        // Global cleanup
    })
    
    Context("Feature or scenario", func() {
        BeforeEach(func() {
            // Per-test setup
            ctx = func() context.Context { return context.Background() }
            log = func() logger.Logger { return logger.New(ctx) }
            v = viper.New(ctx, log)
        })
        
        AfterEach(func() {
            // Per-test cleanup
        })
        
        It("should do something specific", func() {
            // Test implementation
            Expect(result).To(Equal(expected))
        })
    })
})

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Thread Safety

Thread safety is ensured through atomic operations and the underlying viper library's thread-safe design.

Concurrency Primitives

// Atomic hook indexing
atomic.Uint32

// Thread-safe hook storage
libctx.Config[uint8]

// Viper core (thread-safe by design)
*spfvpr.Viper

Verified Components

Component	Mechanism	Status
Viper interface	Underlying viper thread-safety	✅ Race-free
Hook registration	Atomic index + context storage	✅ Race-free
All getter methods	Read-only viper operations	✅ Parallel-safe
Configuration loading	Viper core synchronization	✅ Thread-safe

Testing Commands

# Full suite with race detection
CGO_ENABLED=1 go test -race -v ./...

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

# Stress test
for i in {1..10}; do CGO_ENABLED=1 go test -race ./... || break; done

Result: Zero data races across all test runs

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Test File Organization

File	Purpose	Specs
viper_suite_test.go	Suite initialization	1
viper_test.go	Creation, getters, setters, concurrency	30
config_test.go	Configuration loading and sources	20
unmarshall_test.go	Unmarshalling operations	18
hook_test.go	Custom decode hooks	10
cleaner_test.go	Unset operations	15
error_test.go	Error handling	11

Total Test Code: ~1,519 lines

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Writing Tests

Guidelines

1. Use Descriptive Names

It("should unmarshal nested configuration correctly", func() {
    // Test implementation
})

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

It("should load configuration from file", func() {
    // Arrange
    tempFile := filepath.Join(tempDir, "config.json")
    os.WriteFile(tempFile, []byte(`{"app": {"name": "test"}}`), 0644)
    v.SetConfigFile(tempFile)
    
    // Act
    err := v.Config(level.ErrorLevel, level.InfoLevel)
    
    // Assert
    Expect(err).ToNot(HaveOccurred())
    Expect(v.GetString("app.name")).To(Equal("test"))
})

3. Use Appropriate Matchers

Expect(value).To(Equal(expected))
Expect(err).ToNot(HaveOccurred())
Expect(list).To(ContainElement(item))
Expect(text).To(ContainSubstring("substring"))
Expect(number).To(BeNumerically(">", 0))

4. Always Cleanup Resources

BeforeEach(func() {
    tempDir, _ = os.MkdirTemp("", "viper-test-*")
})

AfterEach(func() {
    os.RemoveAll(tempDir)
})

5. Test Edge Cases - Empty input, nil values, missing files, invalid JSON, etc.

6. Avoid External Dependencies - No remote ETCD servers or external services

Test Template

var _ = Describe("viper/new_feature", func() {
    var (
        ctx context.Context
        log liblog.FuncLog
        v   libvpr.Viper
    )

    BeforeEach(func() {
        ctx = func() context.Context { return context.Background() }
        log = func() liblog.Logger { return liblog.New(ctx) }
        v = libvpr.New(ctx, log)
    })

    Context("When using new feature", func() {
        It("should perform expected behavior", func() {
            // Arrange
            expected := "expected value"
            
            // Act
            result := v.GetSomething()
            
            // Assert
            Expect(result).To(Equal(expected))
        })

        It("should handle error case", func() {
            err := v.SomeOperation()
            Expect(err).To(HaveOccurred())
        })
    })
})

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Best Practices

Test Independence

• ✅ Each test should be independent
• ✅ Use BeforeEach/AfterEach for setup/cleanup
• ✅ Create fresh viper instances per test
• ✅ Clean up temporary files
• ❌ Don't rely on test execution order

Test Data

• Use temporary directories for file tests
• Create configuration files on-demand
• Use descriptive test values
• Test with multiple formats (JSON, YAML, TOML)

Assertions

// ✅ Good
Expect(err).ToNot(HaveOccurred())
Expect(value).To(Equal(expected))

// ❌ Avoid
Expect(value == expected).To(BeTrue())

• Use specific matchers for better error messages
• One behavior per test
• Use GinkgoWriter for debug output

Concurrency Testing

It("should handle concurrent access", func() {
    v.Viper().Set("concurrent.test", "value")
    
    done := make(chan bool, 10)
    for i := 0; i < 10; i++ {
        go func() {
            defer GinkgoRecover()
            Expect(v.GetString("concurrent.test")).To(Equal("value"))
            done <- true
        }()
    }
    
    for i := 0; i < 10; i++ {
        Eventually(done).Should(Receive())
    }
})

• Always run with -race during development
• Test concurrent operations explicitly
• Use GinkgoRecover() in goroutines
• Verify thread safety

Error Handling

// ✅ Good
It("should return error for missing config", func() {
    v.SetConfigFile("/nonexistent/config.yaml")
    err := v.Config(level.ErrorLevel, level.InfoLevel)
    Expect(err).To(HaveOccurred())
})

// ❌ Bad
It("should do something", func() {
    _ = v.Config(level.ErrorLevel, level.InfoLevel) // Don't ignore errors!
})

File Operations

// ✅ Good: Use temporary directories
BeforeEach(func() {
    tempDir, err = os.MkdirTemp("", "viper-test-*")
    Expect(err).ToNot(HaveOccurred())
})

AfterEach(func() {
    os.RemoveAll(tempDir)
})

// ❌ Bad: Hard-coded paths
It("should load config", func() {
    v.SetConfigFile("/tmp/config.yaml") // May conflict with other tests
})

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Troubleshooting

Stale Coverage

go clean -testcache
go test -coverprofile=coverage.out ./...

Parallel Test Failures

• Check for shared resources or global state
• Viper package uses proper isolation (should not fail)

Import Cycles

• Use package viper_test convention to avoid cycles

Race Conditions

# Debug races
CGO_ENABLED=1 go test -race -v ./... 2>&1 | tee race-log.txt
grep -A 20 "WARNING: DATA RACE" race-log.txt

Check for:

• Unprotected shared variable access
• Missing synchronization
• Concurrent writes

CGO Not Available

# Install build tools
# Ubuntu/Debian: sudo apt-get install build-essential
# macOS: brew install gcc

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

Test Timeouts

# Identify hanging tests
ginkgo --timeout=10s

Check for:

• Goroutine leaks
• Unclosed channels
• Deadlocks

Debugging

# Single test
ginkgo --focus="should create version"

# Specific file
ginkgo --focus-file=viper_test.go

# Verbose output
ginkgo -v --trace

Use GinkgoWriter for debug output:

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

Temporary File Cleanup

# If tests leave temp files
find /tmp -name "viper-test-*" -type d -mtime +1 -exec rm -rf {} +

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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: Run tests
        run: go test -v ./...
      
      - name: Race detection
        run: CGO_ENABLED=1 go test -race ./...
      
      - name: Coverage
        run: |
          go test -coverprofile=coverage.out ./...
          go tool cover -func=coverage.out

GitLab CI Example

test:
  image: golang:1.21
  script:
    - go test -v ./...
    - CGO_ENABLED=1 go test -race ./...
    - go test -coverprofile=coverage.out ./...
  coverage: '/total:.*?(\d+\.\d+)%/'

Pre-commit Hook

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

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

echo "Checking coverage..."
go test -cover ./... | grep -E "coverage:" || exit 1

echo "All checks passed!"

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Quality Checklist

Before merging code:

• All tests pass: go test ./...
• Race detection clean: CGO_ENABLED=1 go test -race ./...
• Coverage maintained: ≥70%
• New features have tests
• Error cases tested
• Thread safety validated
• Test duration reasonable (<2s)
• Temporary files cleaned up
• Documentation updated

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Resources

Testing Frameworks

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

Concurrency

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

Viper

• Viper Documentation
• Mapstructure

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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.

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