chore: simplify backend verification

test/openapi-contract.e2e-spec.ts

@@ -0,0 +1,52 @@
+import { INestApplication } from '@nestjs/common';
+import { Test } from '@nestjs/testing';
+import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger';
+import { readFile } from 'node:fs/promises';
+import { resolve } from 'node:path';
+import { AppModule } from './../src/app.module';
+import { configureApp } from './../src/main';
+
+function canonicalize(value: unknown): unknown {
+  if (Array.isArray(value)) return value.map(canonicalize);
+  if (value && typeof value === 'object') {
+    return Object.fromEntries(
+      Object.entries(value)
+        .sort(([left], [right]) => left.localeCompare(right))
+        .map(([key, nestedValue]) => [key, canonicalize(nestedValue)]),
+    );
+  }
+  return value;
+}
+
+describe('OpenAPI contract (integration)', () => {
+  let app: INestApplication;
+
+  beforeAll(async () => {
+    const module = await Test.createTestingModule({
+      imports: [AppModule],
+    }).compile();
+    app = module.createNestApplication();
+    configureApp(app);
+    await app.init();
+  });
+
+  afterAll(() => app.close());
+
+  it('matches the committed frontend OpenAPI snapshot', async () => {
+    const runtimeDocument = SwaggerModule.createDocument(
+      app,
+      new DocumentBuilder()
+        .setTitle('WealthLedger API')
+        .setVersion('v1')
+        .build(),
+    );
+    const snapshot = JSON.parse(
+      await readFile(
+        resolve(__dirname, '../../frontend/src/shared/api/spec/openapi.json'),
+        'utf8',
+      ),
+    ) as unknown;
+
+    expect(canonicalize(runtimeDocument)).toEqual(canonicalize(snapshot));
+  });
+});