Initial

tests/unit/telemetry.test.ts

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+import { describe, it, expect } from 'vitest';
+import { parseTelemetry, computeDeviations, distHaversine, parsePrediction } from '$domain';
+import type { TelemetryPoint, PredictionStage } from '$domain';
+
+const points: TelemetryPoint[] = [
+	{ latitude: 62.0, longitude: 129.0, altitude: 0, datetime: '2026-01-01T00:00:00Z', payload: '{}' },
+	{
+		latitude: 62.05,
+		longitude: 129.1,
+		altitude: 15000,
+		datetime: '2026-01-01T00:30:00Z',
+		payload: '{}'
+	}
+];
+
+describe('parseTelemetry', () => {
+	it('builds a flight path and takes the first sample as launch', () => {
+		const t = parseTelemetry(points);
+		expect(t.flight_path).toEqual([
+			[62.0, 129.0, 0],
+			[62.05, 129.1, 15000]
+		]);
+		expect(t.launch.latlng.lat).toBe(62.0);
+		expect(t.datapoints).toHaveLength(2);
+	});
+
+	it('throws on an empty series', () => {
+		expect(() => parseTelemetry([])).toThrow();
+	});
+});
+
+describe('distHaversine', () => {
+	it('is zero for identical points and ~343 km London→Paris', () => {
+		expect(distHaversine({ lat: 55, lng: 37 }, { lat: 55, lng: 37 })).toBe(0);
+		const d = distHaversine({ lat: 51.5074, lng: -0.1278 }, { lat: 48.8566, lng: 2.3522 });
+		expect(d).toBeGreaterThan(340);
+		expect(d).toBeLessThan(346);
+	});
+});
+
+describe('computeDeviations', () => {
+	// Prediction runs 00:00 → 01:30 along the same corridor as the telemetry.
+	const stages: PredictionStage[] = [
+		{
+			stage: 'ascent',
+			trajectory: [
+				{ altitude: 0, datetime: '2026-01-01T00:00:00Z', latitude: 62.0, longitude: 129.0 },
+				{ altitude: 30000, datetime: '2026-01-01T01:00:00Z', latitude: 62.1, longitude: 129.2 }
+			]
+		},
+		{
+			stage: 'descent',
+			trajectory: [
+				{ altitude: 30000, datetime: '2026-01-01T01:00:00Z', latitude: 62.1, longitude: 129.2 },
+				{ altitude: 0, datetime: '2026-01-01T01:30:00Z', latitude: 62.05, longitude: 129.4 }
+			]
+		}
+	];
+	const prediction = parsePrediction(stages);
+
+	it('matches each sample to the closest prediction point', () => {
+		const devs = computeDeviations(points, prediction);
+		expect(devs).toHaveLength(2);
+		// First sample sits exactly on the predicted launch point.
+		expect(devs[0].horizontal).toBeCloseTo(0, 6);
+		expect(devs[0].vertical).toBe(0);
+		// Second sample is offset from the prediction, both laterally and in altitude.
+		expect(devs[1].horizontal).toBeGreaterThan(0);
+		expect(devs[1].altActual).toBe(15000);
+	});
+
+	it('skips samples outside the prediction window', () => {
+		const outside: TelemetryPoint[] = [
+			{
+				latitude: 62,
+				longitude: 129,
+				altitude: 0,
+				datetime: '2025-12-31T00:00:00Z', // a day early
+				payload: '{}'
+			}
+		];
+		expect(computeDeviations(outside, prediction)).toHaveLength(0);
+	});
+
+	it('returns nothing without telemetry', () => {
+		expect(computeDeviations([], prediction)).toEqual([]);
+	});
+});