ml-kem: add mutation testing and expand test coverage

.github/workflows/mutation-testing.yml

@@ -0,0 +1,94 @@
+name: Mutation Testing
+
+# Minimal permissions for security
+permissions:
+  contents: read
+
+on:
+  # Run weekly on Sundays at 2 AM UTC
+  schedule:
+    - cron: "0 2 * * 0"
+  # Allow manual triggering
+  workflow_dispatch:
+    inputs:
+      package:
+        description: "Package to test (select 'all' for all packages)"
+        required: false
+        default: "all"
+        type: choice
+        options:
+          - all
+          - ml-kem
+          - module-lattice
+          - dhkem
+          - frodo-kem
+          - x-wing
+
+env:
+  CARGO_INCREMENTAL: 0
+  CARGO_TERM_COLOR: always
+
+# Only run one mutation test at a time
+concurrency:
+  group: mutation-testing
+  cancel-in-progress: false
+
+jobs:
+  mutants:
+    name: ${{ matrix.package }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        package:
+          - ml-kem
+          - module-lattice
+          - dhkem
+          - frodo-kem
+          - x-wing
+        # Only filter if a specific package was requested via workflow_dispatch
+        # For push/pull_request events, inputs.package is undefined, so default to 'all'
+        exclude:
+          - package: ${{ (github.event.inputs.package || 'all') != 'all' && (github.event.inputs.package || 'all') != 'ml-kem' && 'ml-kem' || 'NONE' }}
+          - package: ${{ (github.event.inputs.package || 'all') != 'all' && (github.event.inputs.package || 'all') != 'module-lattice' && 'module-lattice' || 'NONE' }}
+          - package: ${{ (github.event.inputs.package || 'all') != 'all' && (github.event.inputs.package || 'all') != 'dhkem' && 'dhkem' || 'NONE' }}
+          - package: ${{ (github.event.inputs.package || 'all') != 'all' && (github.event.inputs.package || 'all') != 'frodo-kem' && 'frodo-kem' || 'NONE' }}
+          - package: ${{ (github.event.inputs.package || 'all') != 'all' && (github.event.inputs.package || 'all') != 'x-wing' && 'x-wing' || 'NONE' }}
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683  # v4.2.2
+        with:
+          persist-credentials: false
+          submodules: recursive
+
+      - uses: dtolnay/rust-toolchain@f7ccc83f9ed1e5b9c81d8a67d7ad1a747e22a561  # stable
+        with:
+          toolchain: stable
+
+      - uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6  # v2.7.8
+        with:
+          prefix-key: mutants-${{ matrix.package }}
+
+      - name: Install cargo-mutants
+        run: cargo install cargo-mutants@26.1.2 --locked
+
+      - name: Run mutation testing
+        run: |
+          cargo mutants --package "${{ matrix.package }}" --all-features -j 2 --timeout 300 2>&1 | tee mutants-output.txt
+          # Extract summary for job summary
+          {
+            echo "## Mutation Testing Results: ${{ matrix.package }}"
+            echo ""
+            echo '```'
+            tail -5 mutants-output.txt
+            echo '```'
+          } >> "$GITHUB_STEP_SUMMARY"
+
+      - name: Upload mutation results
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02  # v4.6.2
+        if: always()
+        with:
+          name: mutants-${{ matrix.package }}
+          path: |
+            mutants.out/
+            mutants-output.txt
+          retention-days: 30

ml-kem/src/algebra.rs

@@ -471,6 +471,11 @@ mod test {
         assert_eq!((&v1 * &v2), const_ntt(6));
         assert_eq!((&v1 * &v3), const_ntt(9));
         assert_eq!((&v2 * &v3), const_ntt(18));
+
+        // Verify inequality (catches PartialEq mutation that returns true unconditionally)
+        assert_ne!(v1, v2);
+        assert_ne!(v1, v3);
+        assert_ne!(v2, v3);
     }
 
     #[test]

ml-kem/src/kem.rs

@@ -440,4 +440,29 @@ mod test {
         seed_test::<MlKem768Params>();
         seed_test::<MlKem1024Params>();
     }
+
+    fn key_inequality_test<P>()
+    where
+        P: KemParams,
+    {
+        let mut rng = UnwrapErr(SysRng);
+
+        // Generate two different keys
+        let dk1 = DecapsulationKey::<P>::generate_from_rng(&mut rng);
+        let dk2 = DecapsulationKey::<P>::generate_from_rng(&mut rng);
+
+        let ek1 = dk1.encapsulation_key();
+        let ek2 = dk2.encapsulation_key();
+
+        // Verify inequality (catches PartialEq mutation that returns true unconditionally)
+        assert_ne!(dk1, dk2);
+        assert_ne!(ek1, ek2);
+    }
+
+    #[test]
+    fn key_inequality() {
+        key_inequality_test::<MlKem512Params>();
+        key_inequality_test::<MlKem768Params>();
+        key_inequality_test::<MlKem1024Params>();
+    }
 }

ml-kem/src/pke.rs

@@ -264,4 +264,26 @@ mod test {
         let invalid_key = [0xFF; 1184];
         assert!(EncryptionKey::<MlKem768Params>::from_bytes(&invalid_key.into()).is_err());
     }
+
+    fn key_inequality_test<P>()
+    where
+        P: PkeParams,
+    {
+        let mut rng = UnwrapErr(SysRng);
+        let d1 = B32::generate_from_rng(&mut rng);
+        let d2 = B32::generate_from_rng(&mut rng);
+
+        let (dk1, _) = DecryptionKey::<P>::generate(&d1);
+        let (dk2, _) = DecryptionKey::<P>::generate(&d2);
+
+        // Verify inequality (catches PartialEq mutation that returns true unconditionally)
+        assert_ne!(dk1, dk2);
+    }
+
+    #[test]
+    fn key_inequality() {
+        key_inequality_test::<MlKem512Params>();
+        key_inequality_test::<MlKem768Params>();
+        key_inequality_test::<MlKem1024Params>();
+    }
 }