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Backtest Expert

  • 1.4k installs
  • 2.5k repo stars
  • Updated July 26, 2026
  • tradermonty/claude-trading-skills

backtest-expert is an agent skill for systematically backtest and stress-test quantitative trading strategies before live use.

About

The backtest-expert skill is designed for systematically backtest and stress-test quantitative trading strategies before live use. Backtest Expert Systematic approach to backtesting trading strategies based on professional methodology that prioritizes robustness over optimistic results. Core Philosophy Goal: Find strategies that "break the least", not strategies that "profit the most" on paper. Invoke when the user develops, tests, or stress-tests quantitative trading strategy backtests.

  • Developing or validating systematic trading strategies.
  • Evaluating whether a trading idea is robust enough for live implementation.
  • Troubleshooting why a backtest might be misleading.
  • Learning proper backtesting methodology.
  • Avoiding common pitfalls (curve-fitting, look-ahead bias, survivorship bias).

Backtest Expert by the numbers

  • 1,414 all-time installs (skills.sh)
  • +64 installs in the week ending Jul 28, 2026 (Skillselion tracking)
  • Ranked #95 of 1,136 Finance & Trading skills by installs in the Skillselion catalog
  • Security screen: LOW risk (skills.sh audit)
  • Data as of Jul 28, 2026 (Skillselion catalog sync)
At a glance

backtest-expert capabilities & compatibility

Capabilities
developing or validating systematic trading stra · evaluating whether a trading idea is robust enou · troubleshooting why a backtest might be misleadi · learning proper backtesting methodology
From the docs

What backtest-expert says it does

Expert guidance for systematic backtesting of trading strategies. Use when developing, testing, stress-testing, or validating quantitative trading strategies. Covers "beating ideas
SKILL.md
Expert guidance for systematic backtesting of trading strategies. Use when developing, testing, stress-testing, or validating quantitative trading strategies. C
SKILL.md
npx skills add https://github.com/tradermonty/claude-trading-skills --skill backtest-expert

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Listed on Skillselion
Installs1.4k
repo stars2.5k
Security audit3 / 3 scanners passed
Last updatedJuly 26, 2026
Repositorytradermonty/claude-trading-skills

How do I systematically backtest and stress-test quantitative trading strategies before live use?

Systematically backtest and stress-test quantitative trading strategies before live use.

Who is it for?

Quant traders validating strategies with rigorous backtesting methodology.

Skip if: Skip for discretionary trading advice without systematic backtest scope.

When should I use this skill?

User develops, tests, or stress-tests quantitative trading strategy backtests.

What you get

Completed backtest-expert workflow with documented commands, files, and expected deliverables.

  • failure case study writeup
  • red-flags checklist
  • documented anti-patterns

Files

SKILL.mdMarkdownGitHub ↗

Backtest Expert

Systematic approach to backtesting trading strategies based on professional methodology that prioritizes robustness over optimistic results.

Core Philosophy

Goal: Find strategies that "break the least", not strategies that "profit the most" on paper.

Principle: Add friction, stress test assumptions, and see what survives. If a strategy holds up under pessimistic conditions, it's more likely to work in live trading.

When to Use This Skill

Use this skill when:

  • Developing or validating systematic trading strategies
  • Evaluating whether a trading idea is robust enough for live implementation
  • Troubleshooting why a backtest might be misleading
  • Learning proper backtesting methodology
  • Avoiding common pitfalls (curve-fitting, look-ahead bias, survivorship bias)
  • Assessing parameter sensitivity and regime dependence
  • Setting realistic expectations for slippage and execution costs

Prerequisites

  • Python 3.9+ (for evaluation script)
  • No API keys required
  • No external data dependencies — metrics are user-provided

Workflow

1. State the Hypothesis

Define the edge in one sentence.

Example: "Stocks that gap up >3% on earnings and pull back to previous day's close within first hour provide mean-reversion opportunity."

If you can't articulate the edge clearly, don't proceed to testing.

2. Codify Rules with Zero Discretion

Define with complete specificity:

  • Entry: Exact conditions, timing, price type
  • Exit: Stop loss, profit target, time-based exit
  • Position sizing: Fixed $$, % of portfolio, volatility-adjusted
  • Filters: Market cap, volume, sector, volatility conditions
  • Universe: What instruments are eligible

Critical: No subjective judgment allowed. Every decision must be rule-based and unambiguous.

3. Run Initial Backtest

Test over:

  • Minimum 5 years (preferably 10+)
  • Multiple market regimes (bull, bear, high/low volatility)
  • Realistic costs: Commissions + conservative slippage

Examine initial results for basic viability. If fundamentally broken, iterate on hypothesis.

4. Stress Test the Strategy

This is where 80% of testing time should be spent.

Parameter sensitivity:

  • Test stop loss at 50%, 75%, 100%, 125%, 150% of baseline
  • Test profit target at 80%, 90%, 100%, 110%, 120% of baseline
  • Vary entry/exit timing by ±15-30 minutes
  • Look for "plateaus" of stable performance, not narrow spikes

Execution friction:

  • Increase slippage to 1.5-2x typical estimates
  • Model worst-case fills (buy at ask+1 tick, sell at bid-1 tick)
  • Add realistic order rejection scenarios
  • Test with pessimistic commission structures

Time robustness:

  • Analyze year-by-year performance
  • Require positive expectancy in majority of years
  • Ensure strategy doesn't rely on 1-2 exceptional periods
  • Test in different market regimes separately

Sample size:

  • Absolute minimum: 30 trades
  • Preferred: 100+ trades
  • High confidence: 200+ trades

5. Out-of-Sample Validation

Walk-forward analysis: 1. Optimize on training period (e.g., Year 1-3) 2. Test on validation period (Year 4) 3. Roll forward and repeat 4. Compare in-sample vs out-of-sample performance

Warning signs:

  • Out-of-sample <50% of in-sample performance
  • Need frequent parameter re-optimization
  • Parameters change dramatically between periods

6. Evaluate Results

Questions to answer:

  • Does edge survive pessimistic assumptions?
  • Is performance stable across parameter variations?
  • Does strategy work in multiple market regimes?
  • Is sample size sufficient for statistical confidence?
  • Are results realistic, not "too good to be true"?

Decision criteria:

  • Deploy: Survives all stress tests with acceptable performance
  • 🔄 Refine: Core logic sound but needs parameter adjustment
  • Abandon: Fails stress tests or relies on fragile assumptions

Use the evaluation script for a structured, quantitative assessment:

python3 skills/backtest-expert/scripts/evaluate_backtest.py \
  --total-trades 150 \
  --win-rate 62 \
  --avg-win-pct 1.8 \
  --avg-loss-pct 1.2 \
  --max-drawdown-pct 15 \
  --years-tested 8 \
  --num-parameters 3 \
  --slippage-tested \
  --output-dir reports/

The script scores across 5 dimensions (Sample Size, Expectancy, Risk Management, Robustness, Execution Realism), detects red flags, and outputs a Deploy/Refine/Abandon verdict.

Key Testing Principles

Punish the Strategy

Add friction everywhere:

  • Commissions higher than reality
  • Slippage 1.5-2x typical
  • Worst-case fills
  • Order rejections
  • Partial fills

Rationale: Strategies that survive pessimistic assumptions often outperform in live trading.

Seek Plateaus, Not Peaks

Look for parameter ranges where performance is stable, not optimal values that create performance spikes.

Good: Strategy profitable with stop loss anywhere from 1.5% to 3.0% Bad: Strategy only works with stop loss at exactly 2.13%

Stable performance indicates genuine edge; narrow optima suggest curve-fitting.

Test All Cases, Not Cherry-Picked Examples

Wrong approach: Study hand-picked "market leaders" that worked Right approach: Test every stock that met criteria, including those that failed

Selective examples create survivorship bias and overestimate strategy quality.

Separate Idea Generation from Validation

Intuition: Useful for generating hypotheses Validation: Must be purely data-driven

Never let attachment to an idea influence interpretation of test results.

Common Failure Patterns

Recognize these patterns early to save time:

1. Parameter sensitivity: Only works with exact parameter values 2. Regime-specific: Great in some years, terrible in others 3. Slippage sensitivity: Unprofitable when realistic costs added 4. Small sample: Too few trades for statistical confidence 5. Look-ahead bias: "Too good to be true" results 6. Over-optimization: Many parameters, poor out-of-sample results

See references/failed_tests.md for detailed examples and diagnostic framework.

Output

  • reports/backtest_eval_<timestamp>.json — structured evaluation with per-dimension scores, red flags, and verdict
  • reports/backtest_eval_<timestamp>.md — human-readable report with dimension table, key metrics, and red flag details

Resources

Methodology Reference

File: references/methodology.md

When to read: For detailed guidance on specific testing techniques.

Contents:

  • Stress testing methods
  • Parameter sensitivity analysis
  • Slippage and friction modeling
  • Sample size requirements
  • Market regime classification
  • Common biases and pitfalls (survivorship, look-ahead, curve-fitting, etc.)

Failed Tests Reference

File: references/failed_tests.md

When to read: When strategy fails tests, or learning from past mistakes.

Contents:

  • Why failures are valuable
  • Common failure patterns with examples
  • Case study documentation framework
  • Red flags checklist for evaluating backtests

Critical Reminders

Time allocation: Spend 20% generating ideas, 80% trying to break them.

Context-free requirement: If strategy requires "perfect context" to work, it's not robust enough for systematic trading.

Red flag: If backtest results look too good (>90% win rate, minimal drawdowns, perfect timing), audit carefully for look-ahead bias or data issues.

Tool limitations: Understand your backtesting platform's quirks (interpolation methods, handling of low liquidity, data alignment issues).

Statistical significance: Small edges require large sample sizes to prove. 5% edge per trade needs 100+ trades to distinguish from luck.

Discretionary vs Systematic Differences

This skill focuses on systematic/quantitative backtesting where:

  • All rules are codified in advance
  • No discretion or "feel" in execution
  • Testing happens on all historical examples, not cherry-picked cases
  • Context (news, macro) is deliberately stripped out

Discretionary traders study differently—this skill may not apply to setups requiring subjective judgment.

Related skills

Forks & variants (1)

Backtest Expert has 1 known copy in the catalog totaling 270 installs. They canonicalize to this original listing.

How it compares

Use backtest-expert after backtests fail when you need structured postmortems and anti-patterns, not when you need payoff chart prototypes or live trading connectors.

FAQ

What does backtest-expert do?

Systematically backtest and stress-test quantitative trading strategies before live use.

When should I use backtest-expert?

User develops, tests, or stress-tests quantitative trading strategy backtests.

Is backtest-expert safe to install?

Review the Security Audits panel on this page before installing in production.

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