An Angular effect that read and wrote its own inputs
An Angular store effect looped forever when its data arrived synchronously, and hung the whole test run.
It could not have worked
A race, an ordering, one column holding two things. The shape ruled it out before the code ran.
Store effects in an Angular app called refresh(), which read and wrote the same signals the effect depended on. When the answer arrived synchronously, the effect re-triggered itself forever, and one store hung the whole test run. A second store had the same shape. Wrapping the reads and writes inside the refresh in untracked fixed both.
A related one: Angular treats <video muted> as a plain attribute, so autoplay would have been blocked on a real device. It needs [muted]="true". Neither showed up as an error. One was a hang, the other would have been a silent failure on the day it went on real hardware.