Awesome Open Source
Awesome Open Source

Carthage compatible Cocoapods compatible


Do not crash when your server lies

What is that?

We all know that the API has a specification. We all write tests to cover happy paths and to cover unhappy paths when work with the API.

It may seem that were pretty safe if we have tests and follow the specification. Well, actually no. Usually it works well in theory, but doesnt really work in practice.

We can write as many tests as we need to cover all edge cases, but that is both time consuming and error prone. The best choice would be is to automate this process.

from Crash-free code with Fuzzer


- (void)test {
  NSDictionary *sample = @{
    @name : @John Doe,
    @age : @42

  UserDeserializer *deserializer = [UserDeserializer new];

  FZRRunner *runner = [FZRRunner runnerWithBuiltinMutationsForSample:sample];

  NSArray *reports = [runner enumerateMutantsUsingBlock:^(NSDictionary *mutant) {
    [deserializer deserializeUser:mutant];

  XCTAssertEqual(reports.count, 0);


Components (used by maintainers)

Get the latest component .make file for Fuzzer.


pod 'Fuzzer', '0.3.2'


Add the line below to your Cartfile to get the latest version of Fuzzer.

github "AlexDenisov/Fuzzer"

Please consider Carthage Documentation if you want to install a specific version of Fuzzer or make any advanced setup.

Note : Carthage support has been introduded in v0.3.1
So older versions of Fuzzer cannot be installed with Carthage.

Building From Source

Typically, you won't have to do this. But if you do, a preferred approach for building from source is using sub-projects.

You can use either of the targets below depending on your needs:

  • Fuzzer-lib-ios-static - for legacy projects (up to iOS 6)
  • Fuzzer-iOS-dynamic - for swift and modern projects

Out of the box

Builtin Mutations

Delete Node Mutation

Removes random key/value pair from a dictionary

Replace Node Mutation

Takes random key from dictionary and replaces its value with a value provided by Node Replacement

Builtin Replacements

  • integer replacement: replaces value with 'random' integer
  • float replacement: replaces value with 'random' float
  • string replacement: replaces value with 'random' string
  • boolean replacement: replaces value with 'random' boolean
  • array replacement: replaces value with 'random' array
  • dictionary replacement: replaces value with 'random' dictionary
  • null replacement: replaces value with [NSNull null]
  • nil replacement: replaces value with nil (leads to removing key/value from dictionary)


MIT, see LICENSE for details