test(graph): verify dependency graph resolution, reverse dependents, and blast radius

tests/projectGraph.test.ts

@@ -0,0 +1,56 @@
+import * as fs from 'node:fs';
+import * as os from 'node:os';
+import * as path from 'node:path';
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { ProjectGraph } from '../src/graph/projectGraph';
+
+describe('ProjectGraph', () => {
+  let tempDir: string;
+
+  beforeEach(() => {
+    tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'proofcode-graph-test-'));
+  });
+
+  afterEach(() => {
+    fs.rmSync(tempDir, { recursive: true, force: true });
+  });
+
+  it('should map imports and compute reverse dependents', async () => {
+    // File A: userService.ts
+    const userPath = path.join(tempDir, 'userService.ts');
+    fs.writeFileSync(
+      userPath,
+      `export function getUser(id: string) { return { id }; }`,
+      'utf8'
+    );
+
+    // File B: orderController.ts imports userService
+    const orderPath = path.join(tempDir, 'orderController.ts');
+    fs.writeFileSync(
+      orderPath,
+      `import { getUser } from './userService';
+export function handleOrder(userId: string) {
+  const user = getUser(userId);
+  return user;
+}`,
+      'utf8'
+    );
+
+    const graph = new ProjectGraph(tempDir);
+    await graph.buildGraph([userPath, orderPath]);
+
+    const dependents = graph.getDependents(userPath);
+    expect(dependents.has(orderPath)).toBe(true);
+
+    const changedLinesMap = new Map<string, number[]>();
+    changedLinesMap.set(userPath, [1]);
+
+    const impact = graph.computeImpact(changedLinesMap);
+    expect(impact.changedFiles).toContain(userPath);
+    expect(impact.changedSymbols).toHaveLength(1);
+    expect(impact.changedSymbols[0].symbolName).toBe('getUser');
+    expect(impact.changedSymbols[0].callers).toHaveLength(1);
+    expect(impact.changedSymbols[0].callers[0].callerName).toBe('handleOrder');
+    expect(impact.untestedCallersCount).toBe(1);
+  });
+});