Add unit test

Author: tohhsinpei

src/database/import.ts

@@ -30,6 +30,7 @@ type ChunkedData = {
 export default class DatabaseImporter {
   private client: Client;
   private limit: pLimit.Limit;
+  nonFatalRetryTimeout = 1000; // To be overriden in tests
 
   constructor(
     private dbUrl: URL,
@@ -140,7 +141,7 @@ export default class DatabaseImporter {
           err.original.code === "ETIMEDOUT";
         if (isTimeoutErr) {
           // RTDB connection timeouts are transient and can be retried
-          await new Promise((res) => setTimeout(res, 1000));
+          await new Promise((res) => setTimeout(res, this.nonFatalRetryTimeout));
           return await doRequest();
         }
         throw err;

src/test/database/import.spec.ts

@@ -5,6 +5,7 @@ import { expect } from "chai";
 
 import DatabaseImporter from "../../database/import";
 import { FirebaseError } from "../../error";
+import { FetchError } from "node-fetch";
 
 const dbUrl = new URL("https://test-db.firebaseio.com/foo");
 const chunkSize = 1024 * 1024 * 10;
@@ -112,4 +113,33 @@ describe("DatabaseImporter", () => {
       /Importing is only allowed for an empty location./
     );
   });
+
+  it("retries non-fatal connection timeout error", async () => {
+    const timeoutErr = new FetchError("connect ETIMEDOUT", "system");
+    timeoutErr.code = "ETIMEDOUT";
+
+    nock("https://test-db.firebaseio.com").get("/foo.json?shallow=true").reply(200);
+    nock("https://test-db.firebaseio.com")
+      .put("/foo/a.json", "100")
+      .once()
+      .replyWithError(timeoutErr);
+    nock("https://test-db.firebaseio.com").put("/foo/a.json", "100").once().reply(200);
+    nock("https://test-db.firebaseio.com")
+      .put("/foo/b.json", JSON.stringify([true, "bar", { f: { g: 0, h: 1 }, i: "baz" }]))
+      .reply(200);
+
+    const importer = new DatabaseImporter(
+      dbUrl,
+      DATA_STREAM,
+      /* importPath= */ "/",
+      chunkSize,
+      concurrencyLimit
+    );
+    importer.nonFatalRetryTimeout = 0;
+
+    const responses = await importer.execute();
+
+    expect(responses).to.have.length(2);
+    expect(nock.isDone()).to.be.true;
+  });
 });