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JSON Parsing Test Suite

A comprehensive test suite for RFC 8259 compliant JSON parsers

This repository was created as an appendix to the article Parsing JSON is a Minefield 💣.


This directory contains several parsers and tiny wrappers to turn the parsers into JSON validators, by returning a specific value.

  • 0 the parser did accept the content
  • 1 the parser did reject the content
  • >1 the process did crash
  • timeout happens after 5 seconds


The name of these files tell if their contents should be accepted or rejected.

  • y_ content must be accepted by parsers
  • n_ content must be rejected by parsers
  • i_ parsers are free to accept or reject content


These files contain weird structures and characters that parsers may understand differently, eg:

  • huge numbers
  • dictionaries with similar keys
  • NULL characters
  • escaped invalid strings

These files were used to produce results/transform.html.


Run all parsers with all files:

$ python3

Run all parsers with a specific file:

$ python3 file.json

Run specific parsers with all files:

$ echo '["Python 2.7.10", "Python 3.5.2"]' > python_only.json
$ python3 --filter=python_only.json

The script writes logs in results/logs.txt.

The script then reads logs.txt and generates results/parsing.html.


Some implementations are not installed on my machine, this repo is supposed to test Haskell implementations.

JSON Parsing Tests


A comprehensive test suite for RFC 8259 compliant JSON parsers




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