Add Mock Storage class for cloud storage

packages/api/test/mock_storage.ts

@@ -0,0 +1,55 @@
+import { Writable } from 'stream'
+
+class MockStorage {
+  buckets: { [name: string]: MockBucket }
+
+  constructor() {
+    this.buckets = {}
+  }
+
+  bucket(name: string) {
+    return this.buckets[name] || (this.buckets[name] = new MockBucket(name))
+  }
+}
+
+export class MockBucket {
+  name: string
+  files: { [path: string]: MockFile }
+
+  constructor(name: string) {
+    this.name = name
+    this.files = {}
+  }
+
+  file(path: string) {
+    return this.files[path] || (this.files[path] = new MockFile(path))
+  }
+}
+
+class MockFile {
+  path: string
+  contents: Buffer
+
+  constructor(path: string) {
+    this.path = path
+    this.contents = Buffer.alloc(0)
+  }
+
+  createWriteStream() {
+    return new MockWriteStream(this)
+  }
+}
+
+class MockWriteStream extends Writable {
+  file: MockFile
+
+  constructor(file: MockFile) {
+    super()
+    this.file = file
+  }
+
+  _write(chunk: Buffer, encoding: string, callback: (error?: Error) => void) {
+    this.file.contents = Buffer.concat([this.file.contents, chunk])
+    callback()
+  }
+}