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