Testing location data with edge cases, not just happy paths
An address in a well mapped city center tells you almost nothing about how your system handles a rural route, a disputed border, or a query near the poles. Test the hard cases deliberately.
Tag
#edge-cases
Set up a fallback when a lookup returns no result
An empty result is a normal, valid response, not an error, and your code needs a deliberate path for handling it.
Handle addresses with no house number
A rural address, a landmark, or a new development without an assigned house number still geocodes correctly, just at a coarser precision than a full street address.
What happens to geocoding near the poles
Near the poles, longitude lines converge to a single point and time zones become almost meaningless. Location software built around ordinary assumptions tends to behave strangely there.
The International Date Line and the requests that cross it
Two points a short distance apart can be on different calendar days entirely, purely because of where the International Date Line happens to run between them.
Leap seconds, UTC, and why they rarely matter to you
Every so often, an extra second gets inserted into UTC to keep it aligned with the Earth's actual rotation. Almost no application needs to think about this directly.
Reverse geocoding accuracy near international borders
A coordinate a few meters from a border can reverse geocode to either country depending on exactly how the border data is drawn. This is a genuinely hard case, not a bug.
Address parsing ambiguity: apartments, units and PO boxes
A single address string can hide several distinct pieces of meaning, and the same abbreviation can mean different things in different countries. Parsing it correctly is harder than it looks.
Daylight saving transitions and the requests that break around them
Twice a year, a range of local times either does not exist or exists twice. Software that assumes every clock time is unambiguous will fail exactly then.