add tests

Author: AbhiPrasad

packages/core/src/baseclient.ts

@@ -360,13 +360,13 @@ export abstract class BaseClient<O extends ClientOptions> implements Client<O> {
    * @inheritDoc
    */
   public on(hook: HookName, callback: HookCallback): void {
-    if (this._hooks[hook]) {
-      // @ts-ignore we cannot enforce the callback to match the hook
-      // while saving bundle size
-      this._hooks[hook].push(callback);
-    } else {
+    if (!this._hooks[hook]) {
       this._hooks[hook] = [];
     }
+
+    // @ts-ignore we cannot enforce the callback to match the hook
+    // while saving bundle size
+    this._hooks[hook].push(callback);
   }
 
   /**

packages/core/test/lib/base.test.ts

@@ -1,4 +1,4 @@
-import type { Event, Span } from '@sentry/types';
+import type { Event, Span, Transaction } from '@sentry/types';
 import { dsnToString, logger, SentryError, SyncPromise } from '@sentry/utils';
 
 import { Hub, makeSession, Scope } from '../../src';
@@ -1730,4 +1730,23 @@ describe('BaseClient', () => {
       expect(clearedOutcomes4.length).toEqual(0);
     });
   });
+
+  describe('hooks', () => {
+    it('should call a startTransaction hook', () => {
+      expect.assertions(1);
+
+      const options = getDefaultTestClientOptions({ dsn: PUBLIC_DSN });
+      const client = new TestClient(options);
+
+      let mockTransaction = {
+        traceId: '86f39e84263a4de99c326acab3bfe3bd',
+      } as Transaction;
+
+      client.on('startTransaction', (transaction: Transaction) => {
+        expect(transaction).toEqual(mockTransaction);
+      });
+
+      client.emit('startTransaction', mockTransaction);
+    });
+  });
 });