diff --git a/SwiftDraw/LayerTree.Builder.Path.Arc.swift b/SwiftDraw/LayerTree.Builder.Path.Arc.swift
index aeb95c8..75561ed 100644
--- a/SwiftDraw/LayerTree.Builder.Path.Arc.swift
+++ b/SwiftDraw/LayerTree.Builder.Path.Arc.swift
@@ -33,9 +33,9 @@ import Foundation
 
 //converts DOM.Path.Arc -> LayerTree.Path.Cubic
 
-private extension Comparable {
+extension Comparable {
     func clamped(to limits: ClosedRange<Self>) -> Self {
-        return min(max(self, limits.lowerBound), limits.upperBound)
+        return min(limits.upperBound, max(limits.lowerBound, self))
     }
 }
 
@@ -43,7 +43,7 @@ private func almostEqual<T: FloatingPoint>(_ a: T, _ b: T) -> Bool {
     return a >= b.nextDown && a <= b.nextUp
 }
 
-private func vectorAngle(ux: LayerTree.Float, uy: LayerTree.Float, vx: LayerTree.Float, vy: LayerTree.Float) -> LayerTree.Float {
+func vectorAngle(ux: LayerTree.Float, uy: LayerTree.Float, vx: LayerTree.Float, vy: LayerTree.Float) -> LayerTree.Float {
     let sign: LayerTree.Float = (ux * vy - uy * vx) < 0.0 ? -1.0 : 1.0
     let dot  = (ux * vx + uy * vy).clamped(to: -1.0...1.0)
     return sign * acos(dot)
diff --git a/SwiftDrawTests/LayerTree.Builder.Path.ArcTests.swift b/SwiftDrawTests/LayerTree.Builder.Path.ArcTests.swift
new file mode 100644
index 0000000..4c7dd6d
--- /dev/null
+++ b/SwiftDrawTests/LayerTree.Builder.Path.ArcTests.swift
@@ -0,0 +1,53 @@
+//
+//  LayerTree.Builder.Path.ArcTests.swift
+//  SwiftDraw
+//
+//  Created by Simon Whitty on 14/2/25.
+//  Copyright 2025 Simon Whitty
+//
+//  Distributed under the permissive zlib license
+//  Get the latest version from here:
+//
+//  https://github.com/swhitty/SwiftDraw
+//
+//  This software is provided 'as-is', without any express or implied
+//  warranty.  In no event will the authors be held liable for any damages
+//  arising from the use of this software.
+//
+//  Permission is granted to anyone to use this software for any purpose,
+//  including commercial applications, and to alter it and redistribute it
+//  freely, subject to the following restrictions:
+//
+//  1. The origin of this software must not be misrepresented; you must not
+//  claim that you wrote the original software. If you use this software
+//  in a product, an acknowledgment in the product documentation would be
+//  appreciated but is not required.
+//
+//  2. Altered source versions must be plainly marked as such, and must not be
+//  misrepresented as being the original software.
+//
+//  3. This notice may not be removed or altered from any source distribution.
+//
+
+
+import XCTest
+@testable import SwiftDraw
+
+final class LayerTreeBuilderPathArcTests: XCTestCase {
+
+    func testClamped() {
+        XCTAssertEqual(5.clamped(to: 0...10), 5)
+        XCTAssertEqual((10.1).clamped(to: 0...10), 10)
+        XCTAssertEqual((-1).clamped(to: 0...10), 0)
+        XCTAssertEqual(Double.infinity.clamped(to: 0...10), 10)
+        XCTAssertEqual((-Double.infinity).clamped(to: 0...10), 0)
+        XCTAssertEqual(Double.nan.clamped(to: 0...10), 0)
+        XCTAssertEqual((-Double.nan).clamped(to: 0...10), 0)
+    }
+
+    func testVectorAngle() {
+        XCTAssertEqual(vectorAngle(ux: 1, uy: 1, vx: 1, vy: 1), 0)
+        XCTAssertEqual(vectorAngle(ux: 1, uy: 1, vx: -1, vy: 1), 1.5707964, accuracy: 0.001)
+        XCTAssertEqual(vectorAngle(ux: 1, uy: 1, vx: .nan, vy: 1), 3.1415925, accuracy: 0.001)
+    }
+}