Strengthen test suite: coverage, property tests, mutation testing

Add three complementary layers of test-quality tooling and close the
gaps they surfaced. The suite was strong but entirely example-based:
coverage proved lines ran, not that a wrong result would fail a test.

Tooling
- c8 coverage (.c8rc.json) with source-map remapping onto TypeScript;
  coverage:ci gate wired into the PR pipeline.
- fast-check property tests (test/prop/) exploring the input space of the
  pure parsing/encoding core: LEB128 round-trips + cross-decoder agreement,
  Cursor crash-fuzz, readForm/skipByForm byte parity, ScVal full-width
  bigint round-trips, wasm-section tiling/strip idempotence, indexForAddress
  vs a linear oracle, mnemonic-rendering totality.
- Stryker mutation testing (stryker.conf.json) mutating the TypeScript and
  rebuilding once via buildCommand; DAP child-process tests excluded via a
  Stryker-specific mocha config. Runs as a non-blocking nightly/on-demand
  CI job, not on the PR critical path.

Bugs found and fixed (test-first)
- stripTypedefs looped forever on a cyclic DWARF typedef chain (DoS hang on
  malformed debug info); added a visited-set cycle guard.
- ScVal integer encoding accepted invalid values: u32/i32 took floats and
  out-of-range values verbatim, and wide ints silently wrapped on overflow
  (2^64 -> 0). Added integer + range validation for all integer types.

Coverage gaps closed
- LiveBackend, KometClient failure/timeout paths, the DWARF v5 line-program
  path, and ScVal error branches.
- Removed one of three duplicated LEB128 decoders (TypeRegistry now reuses
  Cursor); a property test pins the remaining two in agreement.

484 -> 566 tests; lines 89.9% -> 92.9%, branches 85.6% -> 88.0%.

Author: RaoulSchaffranek

.c8rc.json

@@ -0,0 +1,15 @@
+{
+  "all": true,
+  "src": ["src"],
+  "exclude-after-remap": true,
+  "include": ["src/**/*.ts"],
+  "exclude": [
+    "src/**/*.d.ts",
+    "src/debugAdapter/types.ts",
+    "src/sourcemap/SourceMapper.ts"
+  ],
+  "extension": [".ts"],
+  "reporter": ["text", "html", "lcov"],
+  "report-dir": "coverage",
+  "clean": true
+}

.github/workflows/ci.yml

@@ -4,13 +4,19 @@ on:
   push:
     branches: [main]
   pull_request:
+  # Allow running the (slow) mutation-testing job on demand and nightly.
+  workflow_dispatch:
+  schedule:
+    - cron: '0 3 * * *'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
 
 jobs:
   build-and-test:
+    # Skip the fast PR pipeline on the nightly schedule (mutation job runs then).
+    if: github.event_name != 'schedule'
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -33,5 +39,33 @@ jobs:
       - name: Build
         run: npm run build
 
-      - name: Test
-        run: npm test
+      - name: Test with coverage gate
+        run: npm run coverage:ci
+
+  mutation:
+    # Mutation testing multiplies the suite runtime, so it is NOT on the PR
+    # critical path — run it manually (workflow_dispatch) or nightly (schedule).
+    if: github.event_name == 'workflow_dispatch' || github.event_name == 'schedule'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Mutation testing (pure core)
+        run: npm run mutation
+
+      - name: Upload mutation report
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: mutation-report
+          path: reports/mutation
+          if-no-files-found: ignore

.gitignore

@@ -1,6 +1,9 @@
 node_modules/
 dist/
 out/
+coverage/
+reports/
+.stryker-tmp/
 *.vsix
 .DS_Store
 *.log

.mocharc.stryker.json

@@ -0,0 +1,16 @@
+{
+  "spec": [
+    "out/test/**/*.test.js"
+  ],
+  "ignore": [
+    "out/test/dap.test.js",
+    "out/test/dapStepping.test.js",
+    "out/test/dapControlStepping.test.js",
+    "out/test/dapVariables.test.js",
+    "out/test/dapMemoryVariables.test.js",
+    "out/test/integration.node.test.js",
+    "out/test/integration.build.test.js",
+    "out/test/contractBuilder.test.js"
+  ],
+  "timeout": 30000
+}

CHANGELOG.md

@@ -4,6 +4,20 @@ All notable changes to this extension are documented in this file. The format is
 based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and this
 project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+
+- Launch argument encoding now rejects invalid integer values instead of
+  silently accepting them: non-integer and out-of-range `u32`/`i32` values (the
+  SDK encoded these verbatim) and out-of-range wide integers such as `u64`
+  `2^64` (the SDK silently wrapped these to `0`) now raise a clear
+  `ScValEncodeError`.
+- DWARF type resolution no longer hangs on malformed debug info containing a
+  cyclic `typedef`/qualifier chain; `stripTypedefs` now terminates on cycles.
+
+[Unreleased]: https://github.com/runtimeverification/simbolik-komet/compare/v0.0.1...HEAD
+
 ## [0.0.1]
 
 Initial release: time-travel debugging for Stellar/Soroban smart contracts, with