testing-strategy e2e-testing test-assertions cascading-ui hidden-assumptions

Failing tests expose hidden assumptions in cascading forms

Test the disabled state, not just the enabled one — a passing assertion confirms state, not behavior, and failures reveal what you actually built versus what you assumed.

June 9, 2026

Summary

Developers ship features based on passing tests without realizing those tests validate the wrong thing. Testing both poles of a state (enabled/disabled, true/false) catches UX decisions that contradict your mental model before production.

Why it matters

Implementation verdict

Replace single-state assertions (toBeEnabled()) with paired assertions covering both states. Requires writing negative tests for every state transition. Worth implementing now — catches bugs that green CI would hide, zero runtime cost.

Sources

1.A passing test doesn't tell you the system works the way you think it works. It tells you the assertion succeeded given the actual system state
2.The test confirmed a state. Not a behavior. The difference only became visible when I tried to test the opposite and the test failed
3.slotDayEl.value = dayKeys[0]; fillTimeOptionsForDay(dayKeys[0])
4.When slots loaded, the page automatically selected the first available day — without any user input

Dev Signal

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