time for a snapshot

workshop/steps/02-vectors-length/mathv.test.ts

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+import { expect, test } from "bun:test";
+import { vec } from "./given.ts";
+import { dot, length, normalize } from "./mathv.ts";
+
+test("length uses Pythagoras", () => {
+	expect(length(vec(3, 4))).toBe(5);
+	expect(length(vec(0, 0))).toBe(0);
+});
+
+test("normalize gives a unit vector in the same direction", () => {
+	const n = normalize(vec(3, 4));
+	expect(n.x).toBeCloseTo(0.6);
+	expect(n.y).toBeCloseTo(0.8);
+	expect(length(n)).toBeCloseTo(1);
+});
+
+test("normalize of the zero vector is (0,0), not NaN", () => {
+	const n = normalize(vec(0, 0));
+	expect(n).toEqual({ x: 0, y: 0 });
+	expect(Number.isNaN(n.x)).toBe(false);
+	expect(Number.isNaN(n.y)).toBe(false);
+});
+
+test("dot product", () => {
+	expect(dot(vec(1, 0), vec(0, 1))).toBe(0); // perpendicular
+	expect(dot(vec(2, 3), vec(4, 5))).toBe(23); // 8 + 15
+});