Derive fuzzable trait

Author: piotmag769

CHANGELOG.md

@@ -28,6 +28,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - `argent` option for `--type` flag in `account create` and `account import` commands. Use `ready` instead. Old account files with `"type": "argent"` are still loaded correctly.
 
+#### Added
+
+- `#[derive(Fuzzable)]` macro that automatically generates `Fuzzable` trait implementations for structs and enums
+
 ## [0.60.0] - 2026-04-27
 
 ### Forge

crates/forge/tests/data/fuzzing/tests/derive_fuzzable.cairo

@@ -0,0 +1,49 @@
+#[derive(Debug, Drop, Fuzzable)]
+struct InnerStruct {
+    value: u64,
+}
+
+#[derive(Debug, Drop, Fuzzable)]
+struct OuterStruct {
+    inner: InnerStruct,
+    extra: u32,
+}
+
+#[derive(Debug, Drop, Fuzzable)]
+struct MultiField<T> {
+    a: u256,
+    b: u128,
+    c: felt252,
+    flag: bool,
+    signed: i64,
+    address: starknet::ContractAddress,
+    t: T,
+}
+
+#[derive(Debug, Drop, Fuzzable)]
+enum InnerEnum {
+    Red: u8,
+    Green,
+    Blue: u32,
+}
+
+#[derive(Debug, Drop, Fuzzable)]
+enum OuterEnum<T> {
+    North: u8,
+    South,
+    East: InnerEnum,
+    West: OuterStruct,
+    Other: MultiField<T>,
+}
+
+#[fuzzer(runs: 10, seed: 1)]
+#[test]
+fn test_derived_enum(d: OuterEnum<u8>) {
+    println!("{d:?}");
+    let is_north = match d {
+        OuterEnum::North(_) => true,
+        _ => false,
+    };
+    // It fails deterministically since seed is set.
+    assert(is_north, 'expected North');
+}

crates/forge/tests/e2e/fuzzing.rs

@@ -36,7 +36,7 @@ fn fuzzing() {
         [PASS] fuzzing::tests::uint128_arg (runs: 256, [..]
         [PASS] fuzzing::tests::uint256_arg (runs: 256, [..]
         Running 0 test(s) from tests/
-        Tests: 12 passed, 1 failed, 0 ignored, 12 filtered out
+        Tests: 12 passed, 1 failed, 0 ignored, 13 filtered out
         Fuzzer seed: [..]
 
         Failures:
@@ -81,7 +81,7 @@ fn fuzzing_set_runs() {
         [PASS] fuzzing::tests::uint128_arg (runs: 10, [..]
         [PASS] fuzzing::tests::uint256_arg (runs: 10, [..]
         Running 0 test(s) from tests/
-        Tests: 12 passed, 1 failed, 0 ignored, 12 filtered out
+        Tests: 12 passed, 1 failed, 0 ignored, 13 filtered out
         Fuzzer seed: [..]
 
         Failures:
@@ -126,7 +126,7 @@ fn fuzzing_set_seed() {
         [PASS] fuzzing::tests::uint128_arg (runs: 256, [..]
         [PASS] fuzzing::tests::uint256_arg (runs: 256, [..]
         Running 0 test(s) from tests/
-        Tests: 12 passed, 1 failed, 0 ignored, 12 filtered out
+        Tests: 12 passed, 1 failed, 0 ignored, 13 filtered out
         Fuzzer seed: 1234
 
         Failures:
@@ -196,7 +196,7 @@ fn fuzzing_exit_first() {
         Failure data:
             0x32202b2062203d3d2032202b2062 ('2 + b == 2 + b')
 
-        Tests: 0 passed, 1 failed, 0 ignored, 23 filtered out
+        Tests: 0 passed, 1 failed, 0 ignored, 24 filtered out
         Interrupted execution of 1 test(s).
 
         Fuzzer seed: [..]
@@ -232,7 +232,7 @@ fn fuzzing_exit_first_single_fail() {
         Failures:
             fuzzing_integrationtest::exit_first_single_fail::exit_first_fails_test
 
-        Tests: 0 passed, 1 failed, 0 ignored, 23 filtered out
+        Tests: 0 passed, 1 failed, 0 ignored, 24 filtered out
         Interrupted execution of 1 test(s).
         "},
     );
@@ -260,7 +260,7 @@ fn fuzzing_multiple_attributes() {
         [PASS] fuzzing_integrationtest::multiple_attributes::with_should_panic (runs: 256, [..])
         [PASS] fuzzing_integrationtest::multiple_attributes::with_available_gas (runs: 50, [..])
         [PASS] fuzzing_integrationtest::multiple_attributes::with_both (runs: 300, [..])
-        Tests: 3 passed, 0 failed, 1 ignored, 21 filtered out
+        Tests: 3 passed, 0 failed, 1 ignored, 22 filtered out
         "},
     );
 }
@@ -286,7 +286,7 @@ fn generate_arg_cheatcode() {
             "`generate_arg` cheatcode: `min_value` must be <= `max_value`, provided values after deserialization: 101 and 100"
 
         [PASS] fuzzing_integrationtest::generate_arg::use_generate_arg_outside_fuzzer (l1_gas: ~0, l1_data_gas: ~0, l2_gas: ~[..])
-        Tests: 1 passed, 1 failed, 0 ignored, 23 filtered out
+        Tests: 1 passed, 1 failed, 0 ignored, 24 filtered out
         "#},
     );
 }
@@ -337,7 +337,40 @@ fn fuzz_generic_struct() {
         Collected 1 test(s) from fuzzing package
         Running 1 test(s) from tests/
         [PASS] fuzzing_integrationtest::generic_struct::test_generic ([..])
-        Tests: 1 passed, 0 failed, 0 ignored, 24 filtered out
+        Tests: 1 passed, 0 failed, 0 ignored, 25 filtered out
         "},
     );
 }
+
+#[test]
+fn fuzz_derive_fuzzable() {
+    let temp = setup_package("fuzzing");
+
+    let output = test_runner(&temp)
+        .arg("derive_fuzzable")
+        .env("SNFORGE_DETERMINISTIC_OUTPUT", "1")
+        .assert()
+        .code(1);
+
+    assert_stdout_contains(
+        output,
+        indoc! { r#"
+        [..]Compiling[..]
+        [..]Finished[..]
+
+
+        Collected 1 test(s) from fuzzing package
+        Running 1 test(s) from tests/
+        [FAIL] fuzzing_integrationtest::derive_fuzzable::test_derived_enum (runs: 1, arguments: ["OuterEnum::South(())"])
+
+        Failure data:
+            0x6578706563746564204e6f727468 ('expected North')
+
+        Tests: 0 passed, 1 failed, 0 ignored, 25 filtered out
+        Fuzzer seed: [..]
+
+        Failures:
+            fuzzing_integrationtest::derive_fuzzable::test_derived_enum
+        "#},
+    );
+}

crates/snforge-scarb-plugin/src/derives.rs

@@ -0,0 +1 @@
+pub mod fuzzable;