Tell you tomorrow's close.
Nobody can. It shows you how your book behaves when the market moves instead.
The list
Nine things it refuses to do.
Each refusal is a promise about how your numbers are made.
Tell you that you were right.
It runs the test. Sometimes that's the same thing. Often it isn't.
Let you rerun until it passes.
Every retry raises the overfitting bar. The fourth-try winner didn't win.
Fill you at the price you wished for.
Signals fill at the next bar's open, never the close you signaled on.
Grade you on years you already saw.
Backtests are scored only on data the strategy never trained on.
Pull a number out of thin air.
Data-backed Vega answers come with the chart, the source and the query behind them.
Forget how a figure was made.
Every figure keeps the method and data version behind it.
Let your code phone home.
Strategies run sealed, with no network and no secrets.
Touch your money.
We never place an order and never hold a dollar. That's your broker's job.