tests: add Vec + String fuzz harnesses

.github/workflows/build.yml

@@ -50,6 +50,45 @@ jobs:
       - name: Run miri
         run: MIRIFLAGS=-Zmiri-ignore-leaks cargo miri test --features="alloc,defmt,mpmc_large,portable-atomic-critical-section,serde,ufmt,bytes"
 
+  # Run cargo-fuzz tests on nightly
+  testfuzz:
+    name: testfuzz
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Cache cargo dependencies
+        uses: actions/cache@v3
+        with:
+          path: |
+            - ~/.cargo/bin/
+            - ~/.cargo/registry/index/
+            - ~/.cargo/registry/cache/
+            - ~/.cargo/git/db/
+          key: ${{ runner.OS }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.OS }}-cargo-
+
+      - name: Cache build output dependencies
+        uses: actions/cache@v3
+        with:
+          path: target
+          key: ${{ runner.OS }}-build-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.OS }}-build-
+
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: nightly
+
+      - name: Run cargo-fuzz test
+        run:
+          - cargo install --locked cargo-fuzz
+          - cargo +nightly fuzz run fuzz_vec -- -runs=16384 -max_len=4096
+          - cargo +nightly fuzz run fuzz_string -- -runs=16384 -max_len=4096
+
   # Run cargo test
   test:
     name: test

CHANGELOG.md

@@ -9,6 +9,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Make MSRV of 1.87.0 explicit.
 
+### Added
+
+- Added `Vec` fuzz test harness + CI runner.
+
 ## [v0.9.1] - 2025-08-19
 
 ### Added

fuzz/.gitignore

@@ -0,0 +1,4 @@
+target
+corpus
+artifacts
+coverage

fuzz/Cargo.toml

@@ -0,0 +1,28 @@
+[package]
+name = "heapless-fuzz"
+version = "0.0.0"
+publish = false
+edition = "2021"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+
+[dependencies.heapless]
+path = ".."
+
+[[bin]]
+name = "fuzz_vec"
+path = "fuzz_targets/fuzz_vec.rs"
+test = false
+doc = false
+bench = false
+
+[[bin]]
+name = "fuzz_string"
+path = "fuzz_targets/fuzz_string.rs"
+test = false
+doc = false
+bench = false

fuzz/fuzz_targets/fuzz_string.rs

@@ -0,0 +1,41 @@
+#![no_main]
+
+use libfuzzer_sys::fuzz_target;
+
+use heapless::{String, Vec};
+
+fn test_string<const N: usize>(data: &[u8]) {
+    let v16_be = data
+        .chunks_exact(2)
+        .map(|c| u16::from_be_bytes([c[0], c[1]]))
+        .collect::<Vec<u16, N>>();
+
+    let v16_le = data
+        .chunks_exact(2)
+        .map(|c| u16::from_le_bytes([c[0], c[1]]))
+        .collect::<Vec<u16, N>>();
+
+    String::<N>::from_utf16(v16_be.as_slice()).ok();
+    String::<N>::from_utf16(v16_le.as_slice()).ok();
+
+    Vec::<u8, N>::from_slice(data)
+        .map_err(|_| ())
+        .and_then(|v| String::<N>::from_utf8(v).map_err(|_| ()))
+        .ok();
+}
+
+fuzz_target!(|data: &[u8]| {
+    match data.len() {
+        0 => (),
+        len if len <= 16 => test_string::<16>(data),
+        len if len <= 32 => test_string::<32>(data),
+        len if len <= 64 => test_string::<64>(data),
+        len if len <= 128 => test_string::<128>(data),
+        len if len <= 256 => test_string::<256>(data),
+        len if len <= 512 => test_string::<512>(data),
+        len if len <= 1024 => test_string::<1024>(data),
+        len if len <= 2048 => test_string::<2048>(data),
+        len if len <= 4096 => test_string::<4096>(data),
+        _ => (),
+    }
+});

fuzz/fuzz_targets/fuzz_vec.rs

@@ -0,0 +1,27 @@
+#![no_main]
+
+use libfuzzer_sys::fuzz_target;
+
+use heapless::Vec;
+
+fn test_vec<const N: usize>(data: &[u8]) {
+    if let Ok(vec) = Vec::<u8, N>::from_slice(data) {
+        assert_eq!(vec.as_slice(), data);
+    }
+}
+
+fuzz_target!(|data: &[u8]| {
+    match data.len() {
+        0 => (),
+        len if len <= 16 => test_vec::<16>(data),
+        len if len <= 32 => test_vec::<32>(data),
+        len if len <= 64 => test_vec::<64>(data),
+        len if len <= 128 => test_vec::<128>(data),
+        len if len <= 256 => test_vec::<256>(data),
+        len if len <= 512 => test_vec::<512>(data),
+        len if len <= 1024 => test_vec::<1024>(data),
+        len if len <= 2048 => test_vec::<2048>(data),
+        len if len <= 4096 => test_vec::<4096>(data),
+        _ => (),
+    }
+});