0.3.1 • Public • Published


Fuzzer for generative testing of ECMAScript parsers, especially those that implement the SpiderMonkey Reflect.parse API.


npm install -g esfuzz



$ esfuzz --help

  Usage: esfuzz OPT*

  -n, --iterations NUM  use at most NUM programs; default: unlimited
  -d, --max-depth NUM   create ASTs with a height no greater than NUM; default: 8
  --acorn               enable marijnh/acorn parser; default: on
  --es6                 allow ECMAScript 6 features in generated programs
  --esprima             enable ariya/esprima parser; default: on
  --help                display this help message and exit
  --reflect             enable Reflect.parse parser; default: on if it exists
  --reflectjs           enable zaach/reflect.js parser
  --uglifyjs            enable limited support for mishoo/UglifyJS2
  --version             display the version number and exit
  --zeparser            enable limited support for qfox/ZeParser

Module Interface

generate(options) -> SpiderMonkey_AST

Generate a random SpiderMonkey AST that represents a valid ECMAScript program. Available options:

  • maxDepth: create ASTs with a height no greater than this value

render(programAST, format) -> String (JS program)

Render a SpiderMonkey AST as an ECMAScript program. If the format argument is omitted, a random format will be used. Otherwise, the given object must be in the format of escodegen's format option.

fuzz(programAST, parsers) -> void

Takes a SpiderMonkey AST and a list of objects that have a parse method that obeys the SpiderMonkey Reflect.parse API. This function will generate concrete syntax and run it through each parser. If any of the parsers fail to parse the program, an error will be thrown.

fuzzAndRoundtrip(programAST, parsers) -> void

Identical to fuzz, except additionally compares the outputs of each parser to the generated program. If any of the parsers fail to parse the program or fail to generate an AST equivalent to the given one, an error will be thrown.

Package Sidebar


npm i esfuzz

Weekly Downloads






Last publish


  • michaelficarra
  • constellation