[CI] Updates ES_YAML_TESTS_BRANCH to 9.0

Author: picandocodigo

.buildkite/pipeline.yml

@@ -29,7 +29,7 @@ steps:
     env:
       RUBY_VERSION: "{{ matrix.ruby }}"
       STACK_VERSION: 9.0.0-SNAPSHOT
-      ES_YAML_TESTS_BRANCH: main
+      ES_YAML_TESTS_BRANCH: '9.0'
       TRANSPORT_VERSION: "{{ matrix.transport }}"
       RUBY_SOURCE: "{{ matrix.ruby_source }}"
       TEST_SUITE: "platinum"
@@ -62,7 +62,7 @@ steps:
       RUBY_VERSION: "3.4"
       RUBY_SOURCE: "ruby"
       TEST_SUITE: serverless
-      ES_YAML_TESTS_BRANCH: main
+      ES_YAML_TESTS_BRANCH: '9.0'
       QUIET: false
     command: ./.buildkite/run-yaml-tests.sh
     artifact_paths: "elasticsearch-api/tmp/*"

elasticsearch-api/spec/yaml-test-runner/run.rb

@@ -81,7 +81,7 @@ def serverless?
 
 # If we're running in a release branch, download the corresponding branch for tests
 current_branch = `git rev-parse --abbrev-ref HEAD`.strip
-branch = current_branch.match(/[0-9]\.[0-9]+/)&.[](0) || ENV['ES_YAML_TESTS_BRANCH'] || nil
+branch = ENV['ES_YAML_TESTS_BRANCH'] || current_branch.match(/[0-9]\.[0-9]+/)&.[](0) || nil
 Elasticsearch::Tests::Downloader::run(tests_path, branch)
 
 runner = Elasticsearch::Tests::TestRunner.new(CLIENT, tests_path, logger)