pixi-demo/tests/chase/hexGraph.test.ts

import { describe, expect, it } from "vitest";
import {
  axialNeighbors,
  isConnected,
  shortestPath,
  shortestPathLength,
} from "../../src/stages/games/chase/logic/hexGraph";
import type { GameGraph } from "../../src/stages/games/chase/logic/types";

function buildGraph(nodes: GameGraph["nodes"]): GameGraph {
  return {
    nodes,
    edgeList: [],
  };
}

describe("hex graph utilities", () => {
  it("returns 6 axial neighbors", () => {
    const neighbors = axialNeighbors(0, 0);
    expect(neighbors).toEqual([
      [1, 0],
      [1, -1],
      [0, -1],
      [-1, 0],
      [-1, 1],
      [0, 1],
    ]);
  });

  it("finds bfs shortest path length", () => {
    const graph = buildGraph({
      A: { id: "A", q: 0, r: 0, neighbors: ["B"] },
      B: { id: "B", q: 1, r: 0, neighbors: ["A", "C"] },
      C: { id: "C", q: 2, r: 0, neighbors: ["B", "D"] },
      D: { id: "D", q: 3, r: 0, neighbors: ["C"] },
    });

    expect(shortestPathLength(graph, "A", "D")).toBe(3);
    expect(shortestPathLength(graph, "A", "A")).toBe(0);
    expect(shortestPath(graph, "A", "D")).toEqual(["A", "B", "C", "D"]);
  });

  it("returns Infinity when target is unreachable", () => {
    const graph = buildGraph({
      A: { id: "A", q: 0, r: 0, neighbors: ["B"] },
      B: { id: "B", q: 1, r: 0, neighbors: ["A"] },
      C: { id: "C", q: 5, r: 5, neighbors: [] },
    });

    expect(shortestPathLength(graph, "A", "C")).toBe(Infinity);
  });

  it("returns Infinity for invalid from/to nodes", () => {
    const graph = buildGraph({
      A: { id: "A", q: 0, r: 0, neighbors: ["B"] },
      B: { id: "B", q: 1, r: 0, neighbors: ["A"] },
    });

    expect(shortestPathLength(graph, "X", "X")).toBe(Infinity);
    expect(shortestPathLength(graph, "X", "A")).toBe(Infinity);
    expect(shortestPathLength(graph, "A", "X")).toBe(Infinity);
  });

  it("checks graph connectivity", () => {
    const connectedGraph = buildGraph({
      A: { id: "A", q: 0, r: 0, neighbors: ["B"] },
      B: { id: "B", q: 1, r: 0, neighbors: ["A", "C"] },
      C: { id: "C", q: 2, r: 0, neighbors: ["B"] },
    });

    const disconnectedGraph = buildGraph({
      A: { id: "A", q: 0, r: 0, neighbors: ["B"] },
      B: { id: "B", q: 1, r: 0, neighbors: ["A"] },
      C: { id: "C", q: 5, r: 5, neighbors: [] },
    });

    expect(isConnected(connectedGraph)).toBe(true);
    expect(isConnected(disconnectedGraph)).toBe(false);
  });

  it("treats empty and single-node graph as connected", () => {
    const emptyGraph = buildGraph({});
    const singleNodeGraph = buildGraph({
      A: { id: "A", q: 0, r: 0, neighbors: [] },
    });

    expect(isConnected(emptyGraph)).toBe(true);
    expect(isConnected(singleNodeGraph)).toBe(true);
  });
});