Two simulators can run the same strategy over the same data and report opposite results. The difference is rarely the strategy. It is a handful of assumptions most tools tuck away in a settings page. This is the checklist for judging any trading simulator, including ours.
1. Spread
Every trade pays the gap between bid and ask. A simulator that ignores it, or charges a single flat figure for every market, can turn a loser into a winner or the reverse. What matters is a realistic typical spread for the instrument and session, not a snapshot. chartTrigger charges the median of a broker's own historical per-bar spread when one is connected, or a stated typical retail spread on public data, and prints which source it used.
2. Slippage
Fills do not always happen at the price you saw, especially on breakouts and news. A simulator should let you state a figure and apply it against you on entries. Setting it to zero is a choice that favours the strategy.
3. Commission and fees
Raw-spread accounts charge commission per lot. If your account does, leaving it out inflates results on every trade. chartTrigger's assumptions include commission per lot.
4. What happens inside a bar
Bars hide the order in which the high and low occurred. If a stop and a target both lie within one candle, the simulator must guess which came first. The honest default is the pessimistic one. chartTrigger replays each bar as synthetic ticks and assumes the stop hit first when both are possible.
5. Position size and starting equity
Profit in currency depends on the lot size and the value of a pip, and the right value differs by instrument: a lot of EURUSD, gold and Bitcoin are completely different exposures. A simulator that applies one forex-style sizing to everything misstates every non-forex result. chartTrigger prices a lot using each instrument's own contract size.
6. Data quality and length
- Is the history long enough to include different market conditions, such as trends and ranges?
- Are there gaps, or a stale last candle?
- Does the bar count requested actually arrive? Some sources cap a single request and truncate silently.
chartTrigger pages through history to honour long requests, and refuses to evaluate on public data that has gone stale.
7. Resistance to over-fitting
A simulator makes it cheap to try a hundred variations and keep the best. That is the most common way a good-looking result is manufactured. No tool prevents it; you do, by fixing parameters before testing, using a recognised default instead of an optimised one, and checking an earlier and a later period separately.
8. Stated assumptions, next to the result
The test of an honest simulator is whether the assumptions are on the page with the number. A result without its spread, slippage, costs and sizing is a figure with no meaning. Every Proving Ground run lists them, and the trades and the statement export carry them too.
What chartTrigger's simulator does not model
- It is bar-based with synthetic ticks, not a replay of every real tick.
- It does not model overnight swap or rollover charges.
- Fills assume a stated slippage, not the depth of a real order book.
- It is a record of how a rule behaved on past data, and is labelled a historical simulation everywhere it appears.
Common questions
What makes a trading simulator realistic?
Realistic spread, stated slippage, commission, a sensible rule for what happens inside a bar, correct position sizing per instrument, good data, and assumptions shown next to the result.
Why do two simulators give different results for the same strategy?
Usually different assumptions: spread, slippage, commission, intra-bar order of stops and targets, or data. The strategy is often not the cause.
Does chartTrigger model swap or overnight fees?
No. Overnight swap and rollover charges are not modelled, so results for rules that hold positions overnight should be read with that in mind.
Can a trading simulator predict future profits?
No. It shows how logic behaved on data that already exists. A good result is not an indication of future performance.
A simulator with its assumptions showing
Spread, slippage, commission, sizing and data source on every run, and what blocked a rule that never fired.
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Risk note. This article is educational material about how chartTrigger works. It is not investment advice, not a recommendation to trade any instrument, and nothing here forecasts results. Trading leveraged products carries a high risk of loss. Any historical simulation referred to is exactly that — a run over past bars under stated spread and slippage assumptions, not an indication of future performance.