That's a good example, because while they're clearly different things, any distinction you draw between them such as "population > 100k" or "has cathedral" is always going to be a bit arbitrary, and many cities grew organically from villages in an unplanned manner.
Is it? Kent Beck, coiner of unit test, made himself quite clear that a unit test is a test that is independent (i.e. doesn't cause other tests to fail). For all the ridiculous definitions I have come across, I have never once heard anyone call an integration test a test that is dependent (i.e. may cause other tests to fail). In reality, a unit test and an integration test are the same thing.
The post facto attempts at differentiation never make sense. For example, another comment here proposed that a unit test is that which is not dependent on externally mutable dependencies (e.g. the filesystem). But Beck has always been adamant that unit tests should use the "real thing" to the greatest extent possible, including using the filesystem if that's what your application does.
Now, if one test mutates the filesystem in a way that breaks another test, that would violate what Beck calls a unit test. This is probably the source of confusion in the above. Naturally, if you don't touch the file system there is no risk of conflicting with other tests also using the filesystem. But that really misses the point.
There are only two kinds of tests: ones you need and ones you don't. Splitting hairs over names of types of tests is only useful if you're trying to pad a resume.
Implying that integration tests (or vice versa) are legally incorporated like cities, while unit tests are not? What value is there in recognizing a test as a legal entity? Does the, assuming US, legal system even allow incorporation of code? Frankly, I don't think your comparison works.
I think he is not implying a hard line legal standard but as connections and size increase different properties start to emerge humans start to differentiate things based on that, but there is a gradient so we can find examples that are hard to classify.
What differentiates a city from a village is legal status, not size. If size means population, there are cities with 400 inhabitants, villages with 30,000 inhabitants, and vice versa. It is not clear how this pertains to tests.
When unit test was coined, it referred to a test that is isolated from other tests. Integration tests are also isolated from other tests. There is no difference. Again, the post facto attempts to differentiate them all fall flat, pointing to things that have no relevance.
Yup, just like testing. Integration and unit tests depend on location as no two locations can agree on what the terms mean – because all definitions that attempt to differentiate them are ultimately nonsensical. At the end of the day they are the exact same thing.