init

world/world_test.go

@@ -0,0 +1,78 @@
+package world
+
+import (
+	"math"
+	"testing"
+
+	"wh/config"
+	"wh/fixed"
+)
+
+func TestOrbitsAreCirclesAtCommonSpeed(t *testing.T) {
+	cfg := config.Default()
+	asts, _ := Generate(cfg)
+	want := cfg.OrbitSpeed.Float64()
+	for _, a := range asts {
+		o := a.Orbit
+		for _, ts := range []int64{0, 100_000, 777_777, o.Period / 3, o.Period - 1} {
+			p, v := o.State(ts)
+			if r := p.Len().Float64(); math.Abs(r-o.A.Float64()) > 1e-3 {
+				t.Fatalf("asteroid %d t=%d: radius %g, want %g", a.ID, ts, r, o.A.Float64())
+			}
+			if s := v.Len().Float64(); math.Abs(s-want)/want > 1e-5 {
+				t.Fatalf("asteroid %d t=%d: speed %g, want %g", a.ID, ts, s, want)
+			}
+			if d := p.Dot(v).Float64() / (p.Len().Float64() * want); math.Abs(d) > 1e-4 {
+				t.Fatalf("asteroid %d: velocity not tangent (cos=%g)", a.ID, d)
+			}
+			// Inclination bounds the height above the ecliptic.
+			if z := p.Z.Abs().Float64(); z > o.A.Float64()*math.Sin(o.Inc.Float64())*1.001+1e-3 {
+				t.Fatalf("asteroid %d: |z|=%g exceeds inclination bound", a.ID, z)
+			}
+		}
+		// Periodic.
+		p1, _ := o.State(12345)
+		p2, _ := o.State(12345 + o.Period)
+		if d := p1.Sub(p2).Len().Float64(); d > 1 {
+			t.Fatalf("asteroid %d not periodic, off by %g km", a.ID, d)
+		}
+	}
+}
+
+func TestOrbitPlaneMatchesInclination(t *testing.T) {
+	o := Orbit{A: fixed.FromInt(2_000_000), Inc: fixed.FromRatio(3, 10), Node: fixed.FromInt(2)}
+	o.Period = PeriodFor(o.A, fixed.FromInt(3))
+	// The orbit normal is Rz(Node)Rx(Inc) applied to +Z; positions must be
+	// perpendicular to it, and the maximum height is A*sin(Inc).
+	n := fixed.Vec{Z: fixed.One}.RotateX(o.Inc).RotateZ(o.Node)
+	var maxZ float64
+	for k := int64(0); k < 50; k++ {
+		p, _ := o.State(k * o.Period / 50)
+		if d := p.Dot(n).Float64(); math.Abs(d) > 1e-2 {
+			t.Fatalf("position not in the orbital plane: p.n = %g", d)
+		}
+		maxZ = math.Max(maxZ, p.Z.Float64())
+	}
+	if want := o.A.Float64() * math.Sin(0.3); math.Abs(maxZ-want)/want > 0.01 {
+		t.Fatalf("max z = %g, want %g", maxZ, want)
+	}
+}
+
+func TestGenerateDeterministic(t *testing.T) {
+	cfg := config.Default()
+	a1, s1 := Generate(cfg)
+	a2, s2 := Generate(cfg)
+	if len(a1) != cfg.AsteroidCount || s1 != s2 {
+		t.Fatal("mismatch")
+	}
+	for i := range a1 {
+		if a1[i] != a2[i] {
+			t.Fatalf("asteroid %d differs", i)
+		}
+	}
+	cfg.Seed = 2
+	a3, _ := Generate(cfg)
+	if a3[0] == a1[0] {
+		t.Fatal("different seeds should differ")
+	}
+}