We're using test files from various projects here:

https://github.com/maxogden/csv-spectrum
https://github.com/gebi/csv-test
https://github.com/keboola/php-csv/tree/master/tests/Keboola/Csv
https://github.com/fivethirtyeight/data/tree/master/avengers

More tests, especially with various escape/enclosing/delimiter combos would
be welcome.