feat: solution for 'Повторный экзамен #2: Граф с рефлексией на код'

test/graph.test.js

@@ -0,0 +1,79 @@
+const { Graph } = require('../src');
+
+describe('Graph', () => {
+  let g;
+
+  beforeEach(() => {
+    g = new Graph();
+  });
+
+  test('initially empty', () => {
+    expect(g.size()).toBe(0);
+    expect(g.edgesCount()).toBe(0);
+  });
+
+  test('addVertex increases size and adds reflexive edge', () => {
+    g.addVertex('a');
+    expect(g.size()).toBe(1);
+    expect(g.isReflexive()).toBe(true);
+    expect(g.hasEdge('a', 'a')).toBe(true);
+  });
+
+  test('addEdge connects vertices and updates adjacency', () => {
+    g.addEdge('a', 'b');
+    expect(g.size()).toBe(2);
+    expect(g.hasEdge('a', 'b')).toBe(true);
+    expect(g.hasEdge('b', 'a')).toBe(true);
+    expect(g.getNeighbors('a')).toEqual(expect.arrayContaining(['a', 'b']));
+    expect(g.getNeighbors('b')).toEqual(expect.arrayContaining(['a', 'b']));
+  });
+
+  test('removeEdge removes connection', () => {
+    g.addEdge('a', 'b');
+    g.removeEdge('a', 'b');
+    expect(g.hasEdge('a', 'b')).toBe(false);
+    expect(g.hasEdge('b', 'a')).toBe(false);
+    // self-loops remain
+    expect(g.hasEdge('a', 'a')).toBe(true);
+    expect(g.hasEdge('b', 'b')).toBe(true);
+  });
+
+  test('removeVertex removes vertex and incident edges', () => {
+    g.addEdge('a', 'b');
+    g.addEdge('a', 'c');
+    g.removeVertex('a');
+    expect(g.size()).toBe(2);
+    expect(g.hasEdge('b', 'a')).toBe(false);
+    expect(g.hasEdge('c', 'a')).toBe(false);
+    expect(g.hasEdge('b', 'c')).toBe(false);
+  });
+
+  test('edges and edgesCount work correctly', () => {
+    g.addEdge('a', 'b');
+    g.addEdge('b', 'c');
+    g.addEdge('c', 'a');
+    expect(g.edgesCount()).toBe(3);
+    const edges = g.edges();
+    expect(edges).toEqual(expect.arrayContaining([
+      ['a', 'b'],
+      ['b', 'c'],
+      ['c', 'a']
+    ]));
+  });
+
+  test('self-loop handling', () => {
+    g.addVertex('x');
+    expect(g.hasEdge('x', 'x')).toBe(true);
+    g.removeEdge('x', 'x');
+    expect(g.hasEdge('x', 'x')).toBe(false);
+  });
+
+  test('reflexivity can be toggled', () => {
+    g.addVertex('p');
+    g.addVertex('q');
+    g.removeReflexive();
+    expect(g.isReflexive()).toBe(false);
+    g.makeReflexive();
+    expect(g.isReflexive()).toBe(true);
+  });
+});