Detecting resource leaks #

Bombadil provides a parameterized property for catching resource leaks in the web application being tested:

typescriptimport { noResourceLeak } from "@antithesishq/bombadil/browser/extras/resources";

// At most 5MB heap growth within 10 seconds.
export const noHeapLeak = noResourceLeak({
  metric: "js_heap_used",
  growthLimit: 5 * 1024 ** 2,
  windowMillis: 10_000,
});

// At most 500 DOM nodes allocated within 1 second.
export const noDomLeak = noResourceLeak({
  metric: "dom_nodes",
  growthLimit: 500,
  windowMillis: 1_000,
});

The property is a sliding-window invariant — within any window of windowMillis, the chosen metric must not grow by more than growthLimit. The available metric values are:

Metric	Meaning
`"js_heap_used"`	Used JS heap, in bytes
`"js_heap_total"`	Total JS heap, in bytes
`"dom_nodes"`	Live DOM node count
`"js_event_listeners"`	Registered event-listener count
`"layout_objects"`	Layout object count

The JS heap is noisy because of garbage collection. For a more robust detection, watch dom_nodes or js_event_listeners, where a big jump more strongly suggests a leak. If you do watch the JS heap, use a growthLimit that is higher than the usual spikes you see before a GC event, and use a long windowMillis. The inspect command is helpful as it visualizes some of these metrics over time.