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FuzzTest

What is FuzzTest?

FuzzTest is a C++ testing framework for writing and executing fuzz tests, which are property-based tests executed using coverage-guided fuzzing under the hood. Fuzz tests are like regular unit tests, but more generic and more powerful. Instead of saying: "for this specific input, we expect this specific output", we can say: "for these types of input, we expect this generic property to be true". For example:

void MyApiAlwaysSucceedsOnPositiveIntegers(int i) {
  bool success = MyApi(i);
  EXPECT_TRUE(success);
}
FUZZ_TEST(MyApiTest, MyApiAlwaysSucceedsOnPositiveIntegers)
    .WithDomains(/*i:*/fuzztest::Positive<int>());

It is our latest fuzz testing technology and the successor of previously used fuzzing tools, such as libFuzzer. It allows you to write powerful fuzz tests more easily than with previously used fuzz targets. You can use it together with GoogleTest, or other unit testing frameworks, allowing you to write fuzz test side by side with regular unit tests, and just as easily.

It is a first-of-its-kind tool that bridges the gap between fuzzing and property-based testing, as it is both:

  1. a testing framework with a rich API (akin to property-based testing libraries), and
  2. a coverage-guided fuzzing engine (akin to AFL or libFuzzer).

Who is it for?

FuzzTest is for everyone who writes C++ code. (Currently, only C++ is supported.) Fuzz testing is a proven testing technique that has found tens of thousands of bugs. With the FuzzTest framework writing these tests becomes a breeze. Because fuzz tests are more generic, they are more powerful than regular unit tests. They can find tricky edge cases automatically for us, edge cases that most likely we would never think of.

You can write fuzz tests as easily as you write unit tests using GoogleTest for example. Simply use the FUZZ_TEST macro like you would use GoogleTest's TEST macro.

Who uses it?

At Google, FuzzTest is widely used and software engineers love it. It has replaced the old style of writing fuzz targets.

How do I use it?

To get started, read the Quickstart with Bazel or Quickstart with CMake, then take a look at the Overview and the Codelab.

Once you have a high level understanding about fuzz tests, consider reading the rest of the documentation, including the:

I need help!

If you have a question or encounter a bug, please file an issue on GitHub.