Feat(contracts): implement subscription contract invariant testing suite

.github/workflows/invariant-tests.yml

@@ -0,0 +1,97 @@
+name: Contract Invariant Tests
+
+on:
+  push:
+    branches: [main, dev, develop, 'feature/*']
+    paths:
+      - 'contracts/**'
+  pull_request:
+    branches: [main, dev, develop, 'feature/*']
+    paths:
+      - 'contracts/**'
+
+env:
+  RUST_VERSION: '1.85'
+  # Number of proptest cases per property. Increase for deeper fuzzing.
+  PROPTEST_CASES: 200
+
+jobs:
+  # ─────────────────────────────────────────────────────────────────────────
+  # Invariant & Property-Based Tests
+  # ─────────────────────────────────────────────────────────────────────────
+  contract-invariants:
+    name: Subscription Contract Invariant Tests
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ env.RUST_VERSION }}
+
+      - name: Cache Rust dependencies
+        uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: './contracts -> target'
+
+      # ── Run the full invariant test suite ──────────────────────────────
+      - name: Run invariant tests (deterministic scenarios)
+        working-directory: ./contracts
+        env:
+          PROPTEST_CASES: ${{ env.PROPTEST_CASES }}
+        run: |
+          cargo test --test invariants -- --nocapture 2>&1 | tee invariant-test-results.txt
+
+      # ── Run all contract tests to ensure nothing regressed ─────────────
+      - name: Run full contract test suite
+        working-directory: ./contracts
+        run: cargo test --verbose
+
+      # ── Upload test results as artifact ───────────────────────────────
+      - name: Upload invariant test results
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: invariant-test-results
+          path: contracts/invariant-test-results.txt
+          retention-days: 30
+
+  # ─────────────────────────────────────────────────────────────────────────
+  # Extended Fuzz Run (only on pushes to main/dev — not every PR)
+  # ─────────────────────────────────────────────────────────────────────────
+  contract-invariants-extended:
+    name: Extended Invariant Fuzz (1000 cases)
+    runs-on: ubuntu-latest
+    if: github.event_name == 'push' && (github.ref == 'refs/heads/main' || github.ref == 'refs/heads/dev')
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ env.RUST_VERSION }}
+
+      - name: Cache Rust dependencies
+        uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: './contracts -> target'
+
+      - name: Run extended invariant fuzz (1000 cases)
+        working-directory: ./contracts
+        env:
+          PROPTEST_CASES: 1000
+        run: |
+          cargo test --test invariants -- --nocapture 2>&1 | tee extended-fuzz-results.txt
+
+      - name: Upload extended fuzz results
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: extended-fuzz-results
+          path: contracts/extended-fuzz-results.txt
+          retention-days: 30

contracts/.gitignore

@@ -1,2 +1,8 @@
 target/
 Cargo.lock
+
+# Soroban test snapshots (generated at runtime, not source)
+test_snapshots/
+
+# Proptest regression files (generated at runtime)
+**/*.proptest-regressions