Rustelo/info/testing_performance.md

Testing Performance Optimizations

This document outlines the performance optimizations implemented to improve test execution speed in the Rustelo server.

Performance Issues Identified

Before Optimizations

• Total test execution time: ~30 seconds (parallel) / ~60 seconds (sequential)
• 155 tests with various expensive operations
• Primary bottlenecks: Password hashing and syntax highlighting initialization

Root Causes

1. Password Hashing (Argon2)

   • Each PasswordService::new() call used production-grade Argon2 parameters
   • Intentionally slow for security (~100-500ms per hash operation)
   • Multiple tests calling password hashing functions

2. Syntax Highlighting (Syntect)

   • Each ContentRenderer::new() call loaded entire syntax highlighting datasets
   • SyntaxSet::load_defaults_newlines() and ThemeSet::load_defaults() are expensive
   • 6+ content renderer tests each creating new instances

3. Cumulative Effect

   • Many tests performing file I/O, database operations, template rendering
   • Even with parallel execution, slowest operations bottleneck the suite

Optimizations Implemented

1. Fast Password Hashing for Tests

File: server/src/auth/password.rs

/// Create a PasswordService with faster parameters for testing
#[cfg(test)]
pub fn new_for_testing() -> Self {
    // Use minimal but valid parameters for faster testing
    let params = Params::new(1024, 1, 1, None).unwrap(); // 1KB memory, 1 iteration, 1 thread
    let argon2 = Argon2::new(argon2::Algorithm::Argon2id, argon2::Version::V0x13, params);
    Self { argon2 }
}

Impact: Password hashing tests now complete in milliseconds instead of seconds.

2. Lightweight Content Renderer for Tests

File: server/src/content/renderer.rs

/// Create a lightweight ContentRenderer for testing without expensive syntax highlighting
#[cfg(test)]
pub fn new_for_testing() -> Self {
    Self {
        syntax_set: SyntaxSet::new(),
        theme_set: ThemeSet::new(),
        theme_name: "base16-ocean.dark".to_string(),
        enable_syntax_highlighting: false,
        enable_tables: true,
        enable_strikethrough: true,
        enable_tasklists: true,
        enable_footnotes: true,
        enable_smart_punctuation: true,
        custom_css_classes: HashMap::new(),
    }
}

Impact: Content renderer tests finish in <0.01s instead of 0.04s.

3. Test Configuration Fixes

File: server/tests/config_integration_test.rs

Fixed configuration parsing issues that were causing test failures:

• Added missing provider field to email configurations
• Fixed csrf default value assertion (true vs false)
• Updated features configuration to use proper nested TOML structure

Performance Results

After Optimizations

• Configuration tests: All 7 tests passing
• Password hashing tests: ~0.03s (down from several seconds)
• Content renderer tests: ~0.00s (down from 0.04s)
• Overall test suite: Still ~30s due to other operations

Parallel vs Sequential Execution

• Parallel (default): ~30 seconds
• Sequential (RUST_TEST_THREADS=1): ~60 seconds
• Parallelization efficiency: ~50% reduction in total time

Remaining Performance Considerations

While significant improvements were made, the test suite still takes ~30 seconds due to:

1. Template rendering and file I/O operations
2. Database operations (SQLite migrations)
3. Configuration loading and validation
4. Cumulative effect of 155 tests

Best Practices for Future Tests

1. Use test-optimized constructors when available (new_for_testing())
2. Mock expensive operations where possible
3. Use faster algorithms for cryptographic operations in tests
4. Share expensive resources between tests when safe
5. Consider using lazy_static! for expensive one-time initializations

Recommendations for Further Optimization

1. Mock database operations with in-memory alternatives
2. Cache template loading across tests
3. Use test-specific configuration with minimal features enabled
4. Profile individual tests to identify remaining bottlenecks
5. Consider splitting large test suites into smaller, focused modules

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Last updated: Test performance optimizations completed