1 files changed, 24 insertions, 0 deletions
diff --git a/packages/math/point.test.ts b/packages/math/point.test.ts
new file mode 100644
index 0000000..89cc4f8
--- /dev/null
+++ b/packages/math/point.test.ts
@@ -0,0 +1,24 @@
+import { pointFrom, pointRotateRads } from "./point";
+import type { Radians } from "./types";
+
+describe("rotate", () => {
+  it("should rotate over (x2, y2) and return the rotated coordinates for (x1, y1)", () => {
+    const x1 = 10;
+    const y1 = 20;
+    const x2 = 20;
+    const y2 = 30;
+    const angle = (Math.PI / 2) as Radians;
+    const [rotatedX, rotatedY] = pointRotateRads(
+      pointFrom(x1, y1),
+      pointFrom(x2, y2),
+      angle,
+    );
+    expect([rotatedX, rotatedY]).toEqual([30, 20]);
+    const res2 = pointRotateRads(
+      pointFrom(rotatedX, rotatedY),
+      pointFrom(x2, y2),
+      -angle as Radians,
+    );
+    expect(res2).toEqual([x1, x2]);
+  });
+});