diff --git a/packages/core/test/lib/hint.test.ts b/packages/core/test/lib/hint.test.ts
new file mode 100644
index 000000000000..03b755a63c71
--- /dev/null
+++ b/packages/core/test/lib/hint.test.ts
@@ -0,0 +1,96 @@
+import { captureEvent, configureScope } from '@sentry/hub';
+import { getGlobalObject } from '@sentry/utils';
+
+import { initAndBind } from '../../src/sdk';
+import { getDefaultTestClientOptions, TestClient } from '../mocks/client';
+import { AddAttachmentTestIntegration } from '../mocks/integration';
+
+const PUBLIC_DSN = 'https://username@domain/123';
+const sendEvent = jest.spyOn(TestClient.prototype, 'sendEvent');
+
+describe('Hint', () => {
+  beforeEach(() => {
+    TestClient.sendEventCalled = undefined;
+    TestClient.instance = undefined;
+  });
+
+  afterEach(() => {
+    jest.clearAllMocks();
+    delete getGlobalObject().__SENTRY__;
+  });
+
+  describe('attachments', () => {
+    test('can be mutated in beforeSend', () => {
+      expect.assertions(1);
+
+      const options = getDefaultTestClientOptions({
+        dsn: PUBLIC_DSN,
+        beforeSend: (event, hint) => {
+          hint.attachments = [...(hint.attachments || []), { filename: 'another.file', data: 'more text' }];
+          return event;
+        },
+      });
+
+      const client = new TestClient(options);
+      client.captureEvent({});
+
+      const [, hint] = sendEvent.mock.calls[0];
+      expect(hint).toEqual({ attachments: [{ filename: 'another.file', data: 'more text' }] });
+    });
+
+    test('gets passed through to beforeSend and can be further mutated', () => {
+      expect.assertions(1);
+
+      const options = getDefaultTestClientOptions({
+        dsn: PUBLIC_DSN,
+        beforeSend: (event, hint) => {
+          hint.attachments = [...(hint.attachments || []), { filename: 'another.file', data: 'more text' }];
+          return event;
+        },
+      });
+
+      const client = new TestClient(options);
+      client.captureEvent({}, { attachments: [{ filename: 'some-file.txt', data: 'Hello' }] });
+
+      const [, hint] = sendEvent.mock.calls[0];
+      expect(hint).toEqual({
+        attachments: [
+          { filename: 'some-file.txt', data: 'Hello' },
+          { filename: 'another.file', data: 'more text' },
+        ],
+      });
+    });
+
+    test('can be mutated by an integration via event processor', () => {
+      expect.assertions(1);
+
+      const options = getDefaultTestClientOptions({
+        dsn: PUBLIC_DSN,
+        integrations: [new AddAttachmentTestIntegration()],
+      });
+
+      initAndBind(TestClient, options);
+      captureEvent({});
+
+      const [, hint] = sendEvent.mock.calls[0];
+      expect(hint?.attachments).toEqual([{ filename: 'integration.file', data: 'great content!' }]);
+    });
+
+    test('get copied from scope to hint', () => {
+      expect.assertions(1);
+
+      const options = getDefaultTestClientOptions({ dsn: PUBLIC_DSN });
+      initAndBind(TestClient, options);
+
+      configureScope(scope => scope.addAttachment({ filename: 'scope.file', data: 'great content!' }));
+
+      captureEvent({}, { attachments: [{ filename: 'some-file.txt', data: 'Hello' }] });
+
+      const [, hint] = sendEvent.mock.calls[0];
+      expect(hint?.attachments).toEqual([
+        { filename: 'some-file.txt', data: 'Hello' },
+        { filename: 'scope.file', data: 'great content!' },
+      ]);
+    });
+  });
+});
diff --git a/packages/core/test/mocks/integration.ts b/packages/core/test/mocks/integration.ts
index 2e192fb12227..868446665949 100644
--- a/packages/core/test/mocks/integration.ts
+++ b/packages/core/test/mocks/integration.ts
@@ -22,3 +22,16 @@ export class TestIntegration implements Integration {
     });
   }
 }
+
+export class AddAttachmentTestIntegration implements Integration {
+  public static id: string = 'AddAttachmentTestIntegration';
+
+  public name: string = 'AddAttachmentTestIntegration';
+
+  public setupOnce(addGlobalEventProcessor: (callback: EventProcessor) => void): void {
+    addGlobalEventProcessor((event, hint) => {
+      hint.attachments = [...(hint.attachments || []), { filename: 'integration.file', data: 'great content!' }];
+      return event;
+    });
+  }
+}