I recommend a tool I've written, Logstash Filter Verifier. It lets you define inputs that it runs through (possibly a subset of) your Logstash filters and compares the result with what you have defined as the expected output.
What's currently lacking is Logstash 5 support, but I hope I'll be able to address that during the next month. Depending on the kind of filters you have it's possible that you'll be able to use Logstash 2.4 with it until Logstash 5 support is available.