fix(MongoInstance): change "instanceReplState" to get triggered on "transition"

Author: hasezoey

packages/mongodb-memory-server-core/src/util/MongoInstance.ts

@@ -547,9 +547,8 @@ export class MongoInstance extends EventEmitter implements ManagerBase {
       this.debug('stdoutHandler: emitting "instancePrimary"');
       this.emit(MongoInstanceEvents.instancePrimary);
     }
-    if (/member [\d\.:]+ is now in state \w+/i.test(line)) {
-      // "[\d\.:]+" matches "0.0.0.0:0000" (IP:PORT)
-      const state = /member [\d\.:]+ is now in state (\w+)/i.exec(line)?.[1] ?? 'UNKNOWN';
+    if (/transition to \w+ from \w+/i.test(line)) {
+      const state = /transition to (\w+) from \w+/i.exec(line)?.[1] ?? 'UNKNOWN';
       this.emit(MongoInstanceEvents.instanceReplState, state);
 
       if (state !== 'PRIMARY') {

packages/mongodb-memory-server-core/src/util/__tests__/MongoInstance.test.ts

@@ -358,14 +358,14 @@ describe('MongodbInstance', () => {
       it('should emit "instanceReplState" when member state is changed', () => {
         // actual line copied from mongod 4.0.14
         const line =
-          'STDOUT: 2020-09-30T19:41:48.388+0200 I REPL     [replexec-0] Member 127.0.0.1:34765 is now in state STARTUP';
+          '2021-08-27T18:44:01.4895064Z 2021-08-27T18:44:01.471+0000 I REPL     [replication-1] transition to RECOVERING from STARTUP2';
 
         mongod.isInstancePrimary = true;
         mongod.stdoutHandler(line);
 
         expect(events.size).toEqual(2);
         expect(events.get(MongoInstanceEvents.instanceSTDOUT)).toEqual(line);
-        expect(events.get(MongoInstanceEvents.instanceReplState)).toEqual('STARTUP');
+        expect(events.get(MongoInstanceEvents.instanceReplState)).toEqual('RECOVERING');
         expect(mongod.isInstancePrimary).toEqual(false);
       });