Justin Visser
c40e483ee6
Two ways to spend the same education budget: a uniform random sample (spray and pray) vs the highest-degree hubs, ties broken stably towards lower node numbers so the pick is deterministic. The origin is never educated; they post the fake. rng.Shuffle does a seeded Fisher-Yates, so the random pick is reproducible too. min() is a builtin since Go 1.21.
68 lines
2 KiB
Go
68 lines
2 KiB
Go
package engine
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import (
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"slices"
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"testing"
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)
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// starGraph builds a small graph with a known degree ranking:
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// node 0 has degree 5, node 1 degree 3, nodes 2 and 3 degree 2,
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// nodes 4 and 5 degree 1.
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func starGraph() *Graph {
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graph := NewGraph(6)
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for leaf := 1; leaf <= 5; leaf++ {
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graph.AddEdge(0, leaf)
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}
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graph.AddEdge(1, 2)
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graph.AddEdge(1, 3)
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return graph
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}
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func TestEducateMostConnected(t *testing.T) {
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tests := []struct {
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name string
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origin int
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count int
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want []int
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}{
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{name: "picks top degrees, skips origin", origin: 0, count: 2, want: []int{1, 2}},
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{name: "origin can be the biggest hub", origin: 1, count: 2, want: []int{0, 2}},
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{name: "tie breaks to lower node number", origin: 0, count: 3, want: []int{1, 2, 3}},
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{name: "count clamps to available students", origin: 0, count: 99, want: []int{1, 2, 3, 4, 5}},
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{name: "zero count educates nobody", origin: 0, count: 0, want: nil},
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}
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for _, testCase := range tests {
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t.Run(testCase.name, func(t *testing.T) {
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got := EducateMostConnected(starGraph(), testCase.origin, testCase.count)
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if !slices.Equal(got, testCase.want) {
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t.Errorf("EducateMostConnected(origin=%d, count=%d) = %v, want %v",
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testCase.origin, testCase.count, got, testCase.want)
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}
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})
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}
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}
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func TestEducateRandomProperties(t *testing.T) {
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graph := starGraph()
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const origin, count = 0, 3
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educated := EducateRandom(graph, origin, count, newRand(1))
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if len(educated) != count {
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t.Fatalf("len(educated) = %d, want %d", len(educated), count)
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}
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if slices.Contains(educated, origin) {
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t.Errorf("educated %v contains the origin %d", educated, origin)
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}
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for index := 1; index < len(educated); index++ {
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if educated[index] == educated[index-1] {
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t.Errorf("educated %v contains a duplicate", educated)
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}
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}
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// Same seed, same pick; that is the determinism contract.
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repeat := EducateRandom(graph, origin, count, newRand(1))
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if !slices.Equal(educated, repeat) {
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t.Errorf("same seed picked %v then %v", educated, repeat)
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}
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}
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