stryker-js: Potential Memory Leak

Summary

Allocation failed - JavaScript heap out of memory during mutation testing on moderately-sized project module. I’ve tried increasing heap space to 8GB, but it still ultimately OOMs.

Stryker config

module.exports = function(config) {
  config.set({
    testRunner: "mocha",
    mutator: "javascript",
    transpilers: [],
    reporter: ["clear-text", "progress"],
    testFramework: "mocha",
    coverageAnalysis: "perTest",
    mutate: ["src/**/!(*.spec).js"],
    mochaOptions: {
      files: ["index.js", "test/dependencies.js", "src/**/*.spec.js"],
    },
  });
};

Stryker environment

├─┬ stryker@0.24.1
├─┬ stryker-api@0.17.2
├─┬ stryker-html-reporter@0.14.2
├─┬ stryker-javascript-mutator@0.7.2
├─┬ stryker-mocha-framework@0.10.2
├─┬ stryker-mocha-runner@0.12.2

Your Environment

software	version(s)
node	v9.9.0
npm	6.0.0
Operating System	MacOS 10.12.6

Stack Trace

[2018-06-28 14:01:23.999] [INFO] Stryker - 86764 Mutant(s) generated
[2018-06-28 14:01:25.129] [INFO] SandboxPool - Creating 4 test runners (based on CPU count)

<--- Last few GCs --->

[97626:0x103800000]   126169 ms: Mark-sweep 8184.6 (8216.9) -> 8184.6 (8216.9) MB, 88.1 / 0.0 ms  allocation failure GC in old space requested
[97626:0x103800000]   126261 ms: Mark-sweep 8184.6 (8216.9) -> 8184.6 (8215.9) MB, 92.0 / 0.0 ms  last resort GC in old space requested
[97626:0x103800000]   126423 ms: Mark-sweep 8184.6 (8215.9) -> 8184.6 (8215.9) MB, 162.1 / 0.0 ms  last resort GC in old space requested


<--- JS stacktrace --->

==== JS stack trace =========================================

Security context: 0x1c8f1b025529 <JSObject>
    1: fromString(aka fromString) [buffer.js:336] [bytecode=0x1c8fa68fb241 offset=161](this=0x1c8fddf822d1 <undefined>,string=0x1c8f12923071 <Very long string[3403188]>,encoding=0x1c8f1b036441 <String[4]: utf8>)
    2: nextMutant(aka nextMutant) [/Users/jacobbiggs/repos/akitabox/packages/server-modules/node_modules/stryker/src/transpiler/MutantTranspiler.js:~36] [pc=0x3717e3bfad5f](this=0x1c8fdd...

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory
 1: node::Abort() [/usr/local/bin/node]
 2: node::FatalTryCatch::~FatalTryCatch() [/usr/local/bin/node]
 3: v8::internal::V8::FatalProcessOutOfMemory(char const*, bool) [/usr/local/bin/node]
 4: v8::internal::Factory::NewRawOneByteString(int, v8::internal::PretenureFlag) [/usr/local/bin/node]
 5: v8::internal::String::SlowFlatten(v8::internal::Handle<v8::internal::ConsString>, v8::internal::PretenureFlag) [/usr/local/bin/node]
 6: v8::String::WriteUtf8(char*, int, int*, int) const [/usr/local/bin/node]
 7: node::StringBytes::Write(v8::Isolate*, char*, unsigned long, v8::Local<v8::Value>, node::encoding, int*) [/usr/local/bin/node]
 8: node::Buffer::New(v8::Isolate*, v8::Local<v8::String>, node::encoding) [/usr/local/bin/node]
 9: node::Buffer::(anonymous namespace)::CreateFromString(v8::FunctionCallbackInfo<v8::Value> const&) [/usr/local/bin/node]
10: v8::internal::FunctionCallbackArguments::Call(void (*)(v8::FunctionCallbackInfo<v8::Value> const&)) [/usr/local/bin/node]
11: v8::internal::MaybeHandle<v8::internal::Object> v8::internal::(anonymous namespace)::HandleApiCallHelper<false>(v8::internal::Isolate*, v8::internal::Handle<v8::internal::HeapObject>, v8::internal::Handle<v8::internal::HeapObject>, v8::internal::Handle<v8::internal::FunctionTemplateInfo>, v8::internal::Handle<v8::internal::Object>, v8::internal::BuiltinArguments) [/usr/local/bin/node]
12: v8::internal::Builtin_Impl_HandleApiCall(v8::internal::BuiltinArguments, v8::internal::Isolate*) [/usr/local/bin/node]
13: 0x3717e37842fd
Abort trap: 6