Expand description
The determinism preamble.
Injected via Page.addScriptToEvaluateOnNewDocument, so it runs before any
page script on every document — including ones created by navigation.
Why this exists: store screenshot sets rot because they are taken by hand at different moments. One shot says 3:47, the next says 9:12; a list reshuffles; “2 hours ago” becomes “3 days ago”. Freezing the clock and seeding the PRNG makes a rerun reproduce the entire set byte for byte, so the only diffs are the ones you meant to make.
Validated empirically before this code existed: with the preamble, two independent browser launches produced identical PNG hashes across five device sizes; with it disabled, the same page produced different bytes. The negative control is the part that makes that evidence rather than a green check.
Structs§
- Determinism
- Knobs for the injected preamble.