fix: spanner mock now creates unique client setups per project

Wipe can be made by calling spanner.close()

packages/spanner-migrate/src/__tests__/apply.spec.ts

@@ -1,21 +1,23 @@
 import { type Database, Spanner } from '@google-cloud/spanner'
-import type {
-  ExecuteSqlRequest,
-  Transaction,
-} from '@google-cloud/spanner/build/src/transaction'
+import type { ExecuteSqlRequest } from '@google-cloud/spanner/build/src/transaction'
 import { applyDown, applyUp } from '../apply'
 import type { Migration } from '../types'
 
 describe('apply', () => {
+  let spanner: jest.Mocked<Spanner>
   let db: jest.Mocked<Database>
 
   beforeEach(() => {
     // Assume `Database` is mocked globally
-    db = new Spanner()
+    spanner = new Spanner() as jest.Mocked<Spanner>
+    db = spanner
       .instance('my-instance')
       .database('my-database') as jest.Mocked<Database>
     jest.clearAllMocks()
   })
+  afterEach(() => {
+    spanner.close()
+  })
 
   describe('applyUp', () => {
     it('should apply the up script and record the migration', async () => {

packages/spanner-migrate/src/__tests__/db.spec.ts

@@ -15,6 +15,9 @@ describe('prepare', () => {
     instance = spanner.instance('my-instance') as jest.Mocked<Instance>
     database = instance.database('my-database') as jest.Mocked<Database>
   })
+  afterEach(() => {
+    spanner.close()
+  })
   describe('ensure ensureMigrationTable', () => {
     it('checks if table exists', async () => {
       await ensureMigrationTable(database)

packages/spanner-mock/src/spanner.ts

@@ -1,7 +1,12 @@
 import { jest } from '@jest/globals'
 import { createMockInstance } from './instance'
 
-export const createSpanner = () => {
+type SpannerArgs = {
+  projectId?: string
+}
+
+const spannerClients = new Map()
+const createNewSpannerClient = (projectId: string) => {
   const instances = new Map<string, ReturnType<typeof createMockInstance>>()
   return {
     instance: jest.fn((instanceName: string) => {
@@ -10,5 +15,16 @@ export const createSpanner = () => {
       }
       return instances.get(instanceName)
     }),
+    close: jest.fn(() => {
+      spannerClients.delete(projectId)
+    }),
+  }
+}
+
+export const createSpanner = (args: SpannerArgs) => {
+  const projectId = args?.projectId || ''
+  if (!spannerClients.has(projectId)) {
+    spannerClients.set(projectId, createNewSpannerClient(projectId))
   }
+  return spannerClients.get(projectId)
 }