Backtest Quality 99%: Meaning, Settings & Limits

Introduction

When you see “Model Quality 99% / 99.9%” in a backtest, it’s just a proxy for how well the tester reconstructed fine price movements (ticks). It does not mean “profit accuracy = 99%.” Don’t take the number at face value—judge whether a system looks robust in real life using the points below.

Modeling modes (and what they’re good for)

Every tick (real ticks)

Replays actual Bid/Ask ticks from history. It reflects spread widening and wicks better, but results can shift across brokers/data sources.
Use when: ultra-short scalpers where a few pips decide outcomes.
Note: Many EAs don’t need this level of precision.

Every tick (generated from M1)

Builds “synthetic ticks” from 1-minute OHLC. Flash moves and extreme wicks get smoothed, so it’s weak for scalping evaluation.
Use when: getting a high-level view for day-trade to swing EAs.

1-minute OHLC (M1 OHLC)

Decisions use only each minute’s open, high, low, close. The in-bar order of price moves is lost.
Use when: entries/exits happen on ≥M1 and stops/takes are not razor-tight.

Open prices only

Evaluates on each bar’s first price only. In-bar movement is ignored, so stop/limit, trailing, fine TP/SL logic won’t be modeled well.
Use when: H1+ bar systems that act only on bar close—rough, sanity-check runs.

Rule of thumb: the more scalpy the EA, the closer you should model to “Every tick (real ticks)”. The more swing-oriented, the more you can get away with rougher modes for a first pass.

Spread, commissions & slippage (the “realism” layer)

Spread

Spreads expand during news and thin liquidity. Testing at a fixed 1.0 pip can be too kind; live will often be worse. Prefer wider settings and/or time-varying spreads to cover “bad” cases.

MT5 setup notes

• In the tester, click the $ (symbol properties) next to the symbol name, enable “Use custom symbol settings”, then enter Spread (points) manually.
• Default is floating (uses the broker’s historical variable spreads). These histories can be unusually tight; setting a manually wider spread is safer.
  

When does your manual spread actually apply?

• Every tick (real ticks): Generally not applied. The tester uses recorded Bid/Ask (i.e., variable real spreads). If you want tougher conditions here, raise commissions and add delay/slippage.
• Every tick (from M1) / M1 OHLC / Open prices only: Applied. Your manual fixed spread (points) is used (e.g., to derive Ask).

Commissions

Match your broker’s scheme (per side/round-turn, per lot/notional, currency). If omitted or wrong, PF and expectancy are inflated.

Slippage & execution delay

Testers often under-slip vs live. Don’t set execution delay shorter than your real server ping (ms). Run worse-case scenarios (wider spreads, added delay) to check the EA doesn’t break.

Tick data caveats (hidden traps inside “99%”)

• Broker differences: quote precision, tick rules, contract specs vary → results move. Align tests with your actual live account.
• Outliers/gaps: spikes and weekend gaps can swing P/L depending on handling. Check for weird bars.
• Time zones/DST: server time shifts change daily cutoffs and week closes. Keep test and live on the same time basis.

Choosing the test period (don’t cherry-pick)

• Include a mix of trend/range, high/low volatility regimes.
• Cover crash/shock phases (COVID, war headlines, flash crashes, etc.).
• If possible, review longer spans (e.g., 10–20 years) for robustness.
• As a stability cue, aim for ≥ 500 trades on the same logic (ideally ≥ 1,000).

Limits of “99% quality”

• Real execution effects (thin books, requotes, partial fills) can’t be fully replicated.
• VPS latency, terminal load, and human actions (manual stops/lot changes) are out of scope.

Bottom line: treat backtest quality as a reference, not a guarantee.

What beginners should actually do

1. Pick EAs that don’t hinge on tiny ticks. Extreme scalpers (1–few pips edge) or “wick-sensitive” logic depend too much on modeling quirks. Prefer EAs with longer bars, clear logic, and positive RR—they’re less likely to drift live.
2. Prefer EAs with verified live forward results. Public real-account tracking (e.g., Myfxbook verified). Demos and backtests are reference only.
3. Run your own backtests. Vendor tests may fit one broker’s data or understate costs. Test with your broker settings. If an EA blocks user testing, that’s a red flag.
4. Check that live P/L “behaves the same way” as the backtest. On a monthly basis, compare win rate, Avg win/loss (RR), PF, Max DD. They should sit in a similar range. If backtest climbs but live doesn’t, re-check costs, hours, broker.
5. Retest under tougher conditions. Wider spreads, added slippage, exclude news windows—make sure the EA doesn’t collapse.
6. Be skeptical of “too perfect” curves. Sky-high PF, standout win rate, near-zero DD may signal grid/martingale or overfitting. See “optimization traps” to spot these.

Summary

• 99% quality = tick reconstruction, not “99% profit certainty.”
• From a user’s view, the safest path is to choose EAs less sensitive to micro-ticks and with real-account forward history.
• Treat demo/backtests as reference; ultimately verify that your live P/L pattern matches the backtest’s way of making money.

FAQ