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.
Countries with no house numbering system
The street-and-house-number address format feels so universal to anyone who grew up with it that it is easy to forget it is a choice, not a natural law. A meaningful number of countries and regions organize addresses differently, and any geocoding system that assumes every address in the world fits a street-then-number template will fail on them, not because the data is missing, but because the model of what an address looks like is wrong for that place.
Some regions rely on block-and-lot systems, where a building is identified by the block it sits in and a lot number within that block, assigned in the order buildings were constructed rather than sequentially along a street. This means two adjacent buildings can have lot numbers that look unrelated, because the numbering reflects history rather than geography. Other places identify locations primarily by named landmarks, districts, or proximity descriptions rather than any formal numbering scheme at all, particularly in rural or informally developed areas.
There are also increasingly common alternate addressing systems, generally grid or code based, designed specifically for places without traditional street addresses, assigning a short alphanumeric or word-based code to any point on the map regardless of whether a conventional address exists there. These are especially useful in informal settlements, remote areas, or anywhere rapid development has outpaced formal address assignment.
For a geocoding API, this means treating "no valid address format" as a real and expected case rather than an error condition, and it means reverse geocoding needs to fall back sensibly, returning the nearest meaningful description available, whether that is a locality name, a landmark, or a coarser administrative area, rather than failing outright because no house number exists to report.
It also affects how confidence should be read. A city or district level precision in a place without formal house numbering is not a sign of poor data quality, it may be the most precise result that honestly exists for that location. Comparing that result unfavorably against a house level result from a country with dense numbering is comparing two different kinds of ground truth, not two qualities of the same thing.
If you are building for a global audience, test your address input forms and validation logic against addresses from places that do not use conventional numbering, not only against your home market's format. Our reverse geocoding endpoint returns the most precise honest description available for a coordinate, which in these cases may reasonably stop at a locality or landmark level rather than manufacturing a house number that does not exist.