On your larger tables you can use the COPY command to pull out subsets…
COPY (SELECT * FROM mytable WHERE ...) TO '/tmp/myfile.tsv'
COPY mytable FROM 'myfile.tsv'
https://www.postgresql.org/docs/current/static/sql-copy.html
You should consider maintaining a set of development data rather than just pulling a subset of your production. In the case that you’re writing unit tests, you could use the same data that is required for the tests, trying to hit all of the possible use cases.