Check dimensions

toHaveBoundingBox compares the axis-aligned bounds of a subject with the values you expect. It is the first claim most specs make, and the one the quick start uses.

1. Claim one axis

const part = await loadModel({ source: 'box-10x20x30.step', format: 'step' });

expectGeo(part)
  .toHaveBoundingBox({ size: { x: 10 } });

import { readFile } from 'node:fs/promises';import { expectGeo } from 'geospec';import { createModelLoader } from 'geospec/model';import { Engine } from 'geospec-engine/node';const engine = new Engine();const loadModel = createModelLoader({ engine, readSource: async (source) => new Uint8Array(await readFile(source as string)) });const part = await loadModel({ source: 'box-10x20x30.step', format: 'step' });expectGeo(part)  .toHaveBoundingBox({ size: { x: 10 } });await loadModel.dispose();engine.close();

Expect only the axes you care about: this claim checks the width of the 10 × 20 × 30 mm box and leaves height and depth free. Set x to 12 and the claim fails with GEOSPEC_BOUNDING_BOX_MISMATCH; add y: 20 to check a second axis.

2. Read the measurement

A passed or failed claim carries its evidence: the measured min, max, center and size, the expectation the engine applied, and the source it measured, brep for STEP and mesh for triangles.

The box above measures as:

{
  "measured": { "center": [5, 10, 15], "max": [10, 20, 30], "min": [0, 0, 0], "size": [10, 20, 30] },
  "normalizedExpected": { "size": { "x": 10 }, "tolerance": 0.02 },
  "witnesses": { "axisFailures": [], "primitives": [], "source": "brep", "tolerance": 0.02 }
}

A failed claim lists each field that missed under axisFailures, in the diagnostic's details and in the witnesses, with its expected and actual values.

3. Pin the position

const part = await loadModel({ source: 'plate-with-through-bore.step', format: 'step' });

expectGeo(part)
  .toHaveBoundingBox({ size: { x: 40, y: 40, z: 20 } });
expectGeo(part)
  .toHaveBoundingBox([0, 0, 0], [40, 40, 20]);
expectGeo(part)
  .toHaveBoundingBox({ center: { x: 0, y: 0 } });

import { readFile } from 'node:fs/promises';import { expectGeo } from 'geospec';import { createModelLoader } from 'geospec/model';import { Engine } from 'geospec-engine/node';const engine = new Engine();const loadModel = createModelLoader({ engine, readSource: async (source) => new Uint8Array(await readFile(source as string)) });const part = await loadModel({ source: 'plate-with-through-bore.step', format: 'step' });expectGeo(part)  .toHaveBoundingBox({ size: { x: 40, y: 40, z: 20 } });expectGeo(part)  .toHaveBoundingBox([0, 0, 0], [40, 40, 20]);expectGeo(part)  .toHaveBoundingBox({ center: { x: 0, y: 0 } });await loadModel.dispose();engine.close();

size checks extents and ignores where the part sits; two vectors, min and max, check position as well; center fixes position with one point, here on x and y only. The plate is 40 × 40 × 20 mm and centred on the z axis, so the second claim fails on four fields, min.x, min.y, max.x and max.y: change the vectors to [-20, -20, 0] and [20, 20, 20] and it passes.

4. Claim a mesh

const part = await loadModel({ source: 'involute-gear.glb', format: 'glb', sourceUnit: 'mm' });

expectGeo(part)
  .toHaveBoundingBox({ size: { z: 5 } });

import { readFile } from 'node:fs/promises';import { expectGeo } from 'geospec';import { createModelLoader } from 'geospec/model';import { Engine } from 'geospec-engine/node';const engine = new Engine();const loadModel = createModelLoader({ engine, readSource: async (source) => new Uint8Array(await readFile(source as string)) });const part = await loadModel({ source: 'involute-gear.glb', format: 'glb', sourceUnit: 'mm' });expectGeo(part)  .toHaveBoundingBox({ size: { z: 5 } });await loadModel.dispose();engine.close();

The claim reads the same on the gear, a GLB mesh, and the evidence source is mesh. Its 624 triangles span 4.999976634979248 mm in z, inside the default 0.02 mm tolerance: add tolerance: 0 beside size and the claim fails on size.z. A mesh claim charges work units per triangle; Set tolerances and budgets shows this claim refused under a small budget, and states the tolerance rule.

Variations

A negated claim. .not in TypeScript and .not_ in Python ask the engine to show the bounds are not as declared: on the box, not.toHaveBoundingBox({ size: { x: 10 } }) fails with GEOSPEC_NEGATED_MATCH and passes once x is 12.

Combined and empty expectations. size: { x: 40 } with center: { z: 10 } checks one extent and one position on the plate. An expectation with no bound refuses before anything is measured, with GEOSPEC_INVALID_EXPECTATION.

Units. A STEP file declares its unit. A GLB does not, so load a mesh with sourceUnit: 'mm' (source_unit="mm" in Python); without it the gear is read in metres and its z extent measures 4999.976634979248.

Mass and area. Bounds say nothing about material inside them. Check mass properties measures volume, area and centre of mass; the measurement reference lists every field.