sneak/SharedTests/GeometryTests.cs

using Microsoft.Xna.Framework;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;

namespace SemiColinGames.Tests {
  [TestClass]
  public class GeometryTests {
    [TestMethod]
    public void TestIntersectSegmentNotColliding() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(8, 8));
      Assert.IsNull(box.IntersectSegment(new Vector2(-16, -16), new Vector2(32, 0)));
    }

    [TestMethod]
    public void TestIntersectSegmentHit() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(8, 8));
      var point = new Vector2(-16, 4);
      var delta = new Vector2(32, 0);
      Hit? maybeHit = box.IntersectSegment(point, delta);

      Assert.IsNotNull(maybeHit);
      Hit hit = (Hit) maybeHit;

      Assert.AreEqual(box, hit.Collider);
      Assert.AreEqual(0.25, hit.Time);

      Assert.AreEqual(point.X + delta.X * hit.Time, hit.Position.X);
      Assert.AreEqual(point.Y + delta.Y * hit.Time, hit.Position.Y);

      Assert.AreEqual((1.0f - hit.Time) * -delta.X, hit.Delta.X);
      Assert.AreEqual((1.0f - hit.Time) * -delta.Y, hit.Delta.Y);

      Assert.AreEqual(-1, hit.Normal.X);
      Assert.AreEqual(0, hit.Normal.Y);
    }

    [TestMethod]
    public void TestIntersectSegmentFromInsideBox() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(8, 8));
      var point = new Vector2(-4, 4);
      var delta = new Vector2(32, 0);
      Hit? maybeHit = box.IntersectSegment(point, delta);

      Assert.IsNotNull(maybeHit);
      Hit hit = (Hit) maybeHit;

      Assert.AreEqual(box, hit.Collider);
      Assert.AreEqual(0.0, hit.Time);

      Assert.AreEqual(-4, hit.Position.X);
      Assert.AreEqual(4, hit.Position.Y);

      Assert.AreEqual(-delta.X, hit.Delta.X);
      Assert.AreEqual(-delta.Y, hit.Delta.Y);

      Assert.AreEqual(-1, hit.Normal.X);
      Assert.AreEqual(0, hit.Normal.Y);
    }

    [TestMethod]
    public void TestIntersectSegmentWithPadding() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(8, 8));
      var point = new Vector2(-16, 4);
      var delta = new Vector2(32, 0);
      int padding = 4;
      Hit? maybeHit = box.IntersectSegment(point, delta, new Vector2(padding, padding));

      Assert.IsNotNull(maybeHit);
      Hit hit = (Hit) maybeHit;

      Assert.AreEqual(box, hit.Collider);
      Assert.AreEqual(0.125, hit.Time);

      Assert.AreEqual(point.X + delta.X * hit.Time, hit.Position.X);
      Assert.AreEqual(point.Y + delta.Y * hit.Time, hit.Position.Y);

      Assert.AreEqual((1.0f - hit.Time) * -delta.X, hit.Delta.X);
      Assert.AreEqual((1.0f - hit.Time) * -delta.Y, hit.Delta.Y);

      Assert.AreEqual(-1, hit.Normal.X);
      Assert.AreEqual(0, hit.Normal.Y);
    }

    [TestMethod]
    public void TestIntersectSegmentFromTwoDirections() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(32, 32));
      var farPos = new Vector2(64, 0);
      var farToNearDelta = new Vector2(-32, 0);
      Assert.IsNull(box.IntersectSegment(farPos, farToNearDelta));

      var nearPos = new Vector2(32, 0);
      var nearToFarDelta = new Vector2(32, 0);
      Assert.IsNull(box.IntersectSegment(nearPos, nearToFarDelta));
    }

    [TestMethod]
    public void TestIntersectSegmentXAxisAligned() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(16, 16));
      var pos = new Vector2(-32, 0);
      var delta = new Vector2(64, 0);
      Hit? maybeHit = box.IntersectSegment(pos, delta);

      Assert.IsNotNull(maybeHit);
      Hit hit = (Hit) maybeHit;

      Assert.AreEqual(0.25, hit.Time);
      Assert.AreEqual(-1, hit.Normal.X);
      Assert.AreEqual(0, hit.Normal.Y);
    }

    [TestMethod]
    public void TestIntersectSegmentYAxisAligned() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(16, 16));
      var pos = new Vector2(0, -32);
      var delta = new Vector2(0, 64);
      Hit? maybeHit = box.IntersectSegment(pos, delta);

      Assert.IsNotNull(maybeHit);
      Hit hit = (Hit) maybeHit;

      Assert.AreEqual(0.25, hit.Time);
      Assert.AreEqual(0, hit.Normal.X);
      Assert.AreEqual(-1, hit.Normal.Y);
    }
  }
}