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Version: v1.1.x

Features

The Node Tree Adapter Plugin provides an alternative object generation engine for Fixture Monkey. It replaces the default generation path with a JvmNodeTree-based architecture that delivers better performance and built-in debugging capabilities.

info

Starting from v1.2.0, the Node Tree Adapter will become the default object generation engine. We recommend adopting it early to prepare for the transition.

Why Use This Plugin?​

  • Zero overhead — benchmark tests show no performance penalty compared to the default path
  • Faster thenApply — approximately 10% faster than the default engine for thenApply operations
  • Built-in tracing — debug exactly how values are resolved during fixture generation
  • Deterministic output — fixed seed support for reproducible test results

Setup​

FixtureMonkey fixtureMonkey = FixtureMonkey.builder()
    .plugin(new JavaNodeTreeAdapterPlugin())
    .build();

Compatible with other plugins — just add it alongside your existing plugins:

FixtureMonkey fixtureMonkey = FixtureMonkey.builder()
    .plugin(new JavaNodeTreeAdapterPlugin())
    .plugin(new JakartaValidationPlugin())
    .plugin(new SimpleValueJqwikPlugin())
    .build();

Benchmark Results​

Measured with JMH (fork=1, warmup=3, iterations=10), generating 200 OrderSheet objects per iteration.

ScenarioWithout Adapter (ms)With Adapter (ms)Overhead
Pure sample125.2121.4-3.1%
set121.7120.7-0.8%
size + setNull122.6123.4+0.6%
Nested set124.1124.8+0.5%
thenApply333.3301.1-9.7%

All scenarios show near-zero overhead. thenApply is consistently ~10% faster with the adapter.

Configuration​

Seed​

Set a fixed seed for reproducible results:

FixtureMonkey fixtureMonkey = FixtureMonkey.builder()
    .plugin(new JavaNodeTreeAdapterPlugin()
        .seed(12345L))
    .build();
caution

The seed feature is not yet fully supported. Reproducibility is not guaranteed in all scenarios. Full seed support is planned for a future release.

Tracer​

Enable tracing to debug how values are resolved during fixture generation:

FixtureMonkey fixtureMonkey = FixtureMonkey.builder()
    .plugin(new JavaNodeTreeAdapterPlugin()
        .tracer(AdapterTracer.console()))
    .build();

Available Tracers​

TracerDescription
AdapterTracer.noOp()No tracing (default)
AdapterTracer.console()Print tree-formatted trace to console
AdapterTracer.consoleJson()Print JSON-formatted trace to console
AdapterTracer.timing()Print timing information
AdapterTracer.file(path)Write trace to a file (append mode)

Example Trace Output​

[AdapterTracer] ── OrderSheet ──────────────────
  Resolution:
    $.orderProducts  → container size = 2
    $.orderProducts[0].productName  → set("product-0")
  Assembly:
    $ (OrderSheet) → BeanArbitraryIntrospector
      $.id (String) → "aB3xK"
      $.userNo (Long) → 42
      $.orderProducts (List) → size=2
        $.orderProducts[0] (OrderProduct)
          $.orderProducts[0].productName → "product-0" [USER_SET]

Enable / Disable​

The plugin is enabled by default. To disable it conditionally:

FixtureMonkey fixtureMonkey = FixtureMonkey.builder()
    .plugin(new JavaNodeTreeAdapterPlugin()
        .enabled(false))  // disables the adapter, uses default path
    .build();