[8.19] [Security Solution] Wait for Fleet setup completion in OOM tests (elastic#239900) (elastic#240287)

# Backport

This will backport the following commits from `main` to `8.19`:
- [[Security Solution] Wait for Fleet setup completion in OOM tests
(elastic#239900)](elastic#239900)

<!--- Backport version: 9.6.6 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sorenlouv/backport)

<!--BACKPORT [{"author":{"name":"Maxim
Palenov","email":"[email protected]"},"sourceCommit":{"committedDate":"2025-10-23T13:15:25Z","message":"[Security
Solution] Wait for Fleet setup completion in OOM tests
(elastic#239900)\n\n**Partially addresses:**
https://github.com/elastic/kibana/issues/188090\n\n## Summary\n\nThere
is a race condition between Fleet plugin setup and FTR tests performing
prebuilt rules package installation. To mitigate the risk of flakiness
this PR introduces Fleet plugin setup awaiting in the prebuilt rules OOM
tests.","sha":"70d327178de4d436b0dd35e30f8d92d6323b7f38","branchLabelMapping":{"^v9.3.0$":"main","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["release_note:skip","Team:Detections
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Solution] Wait for Fleet setup completion in OOM
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Solution] Wait for Fleet setup completion in OOM tests
(elastic#239900)\n\n**Partially addresses:**
https://github.com/elastic/kibana/issues/188090\n\n## Summary\n\nThere
is a race condition between Fleet plugin setup and FTR tests performing
prebuilt rules package installation. To mitigate the risk of flakiness
this PR introduces Fleet plugin setup awaiting in the prebuilt rules OOM
tests.","sha":"70d327178de4d436b0dd35e30f8d92d6323b7f38"}},"sourceBranch":"main","suggestedTargetBranches":["9.2","9.1","8.19"],"targetPullRequestStates":[{"branch":"9.2","label":"v9.2.0","branchLabelMappingKey":"^v(\\d+).(\\d+).\\d+$","isSourceBranch":false,"state":"NOT_CREATED"},{"branch":"9.1","label":"v9.1.3","branchLabelMappingKey":"^v(\\d+).(\\d+).\\d+$","isSourceBranch":false,"state":"NOT_CREATED"},{"branch":"main","label":"v9.3.0","branchLabelMappingKey":"^v9.3.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/239900","number":239900,"mergeCommit":{"message":"[Security
Solution] Wait for Fleet setup completion in OOM tests
(elastic#239900)\n\n**Partially addresses:**
https://github.com/elastic/kibana/issues/188090\n\n## Summary\n\nThere
is a race condition between Fleet plugin setup and FTR tests performing
prebuilt rules package installation. To mitigate the risk of flakiness
this PR introduces Fleet plugin setup awaiting in the prebuilt rules OOM
tests.","sha":"70d327178de4d436b0dd35e30f8d92d6323b7f38"}},{"branch":"8.19","label":"v8.19.6","branchLabelMappingKey":"^v(\\d+).(\\d+).\\d+$","isSourceBranch":false,"state":"NOT_CREATED"}]}]
BACKPORT-->

Co-authored-by: Maxim Palenov <[email protected]>

Author: kibanamachine

x-pack/solutions/security/test/security_solution_api_integration/test_suites/detections_response/rules_management/prebuilt_rules/oom_testing/install_prebuilt_rules/install_prebuilt_rules.ts

@@ -26,6 +26,8 @@ import {
 } from '../../../../utils/rules/prebuilt_rules/delete_fleet_packages';
 import { deleteAllRules, waitFor } from '../../../../../../config/services/detections_response';
 
+const KIBANA_STATUS_URL = '/api/status';
+
 export default ({ getService }: FtrProviderContext): void => {
   const es = getService('es');
   const supertest = getService('supertest');
@@ -35,6 +37,31 @@ export default ({ getService }: FtrProviderContext): void => {
 
   describe('@ess @serverless @skipInServerlessMKI Install from mocked prebuilt rule assets', () => {
     beforeEach(async () => {
+      await waitFor(
+        async () => {
+          const { body: kibanaStatusResponse } = await supertest
+            .get(KIBANA_STATUS_URL)
+            .send()
+            .expect(200);
+
+          if (kibanaStatusResponse.status.plugins.fleet.summary === 'Fleet setup failed') {
+            throw new Error(
+              `Fleet setup failed: ${JSON.stringify(
+                kibanaStatusResponse.status.plugins.fleet,
+                null,
+                2
+              )}`
+            );
+          }
+
+          return kibanaStatusResponse.status.plugins.fleet.summary === 'Fleet is available';
+        },
+        'waitForFleetSetup',
+        log,
+        undefined, // maxTimeout - use default
+        3000 // timeoutWait - wait longer between tries as fleet setup can take some time
+      );
+
       await deleteAllRules(supertest, log);
 
       await deletePrebuiltRulesFleetPackage({ supertest, es, log, retryService });