CSHARP-5840: Proper XUnit shared test fixture for Atlas tests (#2007)

* Self-seed Atlas Search test data via shared XUnit fixture

Replaces the suite's dependence on pre-configured Atlas sample databases
and search indexes. The new AtlasSearchFixture (collection-scoped) owns
a single client, an EventCapturer, and a fixture-managed
atlas_search_<guid> database. Lazy seeders populate historical_documents,
movies, embedded_movies, airbnb_listings, test_classes, binary_vector_items,
auto_embed_movies, two synonym source collections, and the existing
return-scope directors collection, and create the ten search/vector
indexes required by the tests (waiting for READY). Dispose drops the
whole database.

The seed data is baked in as C# literals in AtlasSearchFixtureSeedData.cs
(generated by tests/Tools/AtlasSeedExtractor from Atlas Local sample
data once) so the test suite has zero runtime dependency on sample
databases — only on an Atlas-search-capable cluster being reachable at
ATLAS_SEARCH_URI. Embeddings are preserved as real Voyage-AI float32
vectors via BinaryVectorFloat32.

AtlasSearchTests, VectorSearchTests, AutoEmbedVectorSearchTests, and
AtlasSearchIndexManagementTests join via [Collection(AtlasSearchCollection.Name)]
and pull their client / collections through the fixture. AtlasSearchTests
loses its static __indexesCreated / __databaseUniquifier /
__returnScopeTestCount machinery and the inline return-scope seed.
AtlasSearchTestsUtils is obsoleted.

AutoEmbedVectorSearchTests now run for real (the previous CSHARP-5840
skip is gone): the auto-embed collection and index live in the fixture
so the Voyage AI embedding work happens once per test session instead
of three times, the corpus is reduced to 4 movies (2 pass the
runtime+year filter, 2 don't), and the ctor's unbounded wait loop is
replaced with a 15-minute deadline that surfaces a clear error mentioning
VOYAGE_API_KEY. Gated on a new AUTO_EMBEDDING_TESTS_ENABLED env var so contributors
without a Voyage AI key can still run the rest of the Atlas Search
suite. When enabled, the Atlas Local container must have
VOYAGE_API_KEY provisioned via the Atlas UI's Model API Keys page (the
key must authenticate against ai.mongodb.com, not api.voyageai.com).
docker-compose.atlas-local.yml is included as a convenience launcher.

Count- and ranking-dependent assertions are recalibrated for the lean
corpus: phrase-match counts drop from 108 to 1, geo-result counts from
25 to membership checks, and vector-search top-K assertions switch from
order-sensitive ShouldBeEquivalentTo to order-insensitive BeEquivalentTo.
The Pinocchio→Oz swap in VectorSearch top-5 is documented in the test
where it lives. The Rerank test guards on AtlasSearchFixture.IsRerankSupported,
which probes the deployment on first use.

Validated against Atlas Local: 77/77 AtlasSearch* tests pass, 36/36
AtlasSearchIndexManagement tests pass, 3/3 AutoEmbedVectorSearchTests
pass (with a valid VOYAGE_API_KEY), 74 tests skip cleanly when env vars
are unset, and no atlas_search_* databases remain after the suite exits.

[review-iter 1] Address review findings

[review-iter 2] Address review findings

* Copilot feedback

* Review feedback

* Remove atlas-search-index-helpers-test

* Remove AtlasSeedExtractor tool and simplify fixture init locking

The AtlasSeedExtractor project was a one-shot generator that produced the
baked-in literals in AtlasSearchFixtureSeedData.cs. That seed data is now
static and checked in, so the tool is no longer needed: delete the project
and drop the generator references from the seed-data file header.

Also collapse the eight near-identical double-checked-locking blocks in
AtlasSearchFixture into a single EnsureInitialized(isInitialized, initialize)
helper, and mark the per-collection init guards volatile so the lock-free
fast-path read is correctly published. Behavior is unchanged: the shared
_initLock still serializes seeding, and a throwing seeder still leaves its
guard unset so the next access retries (unlike Lazy<T>, which would cache
and re-throw the failure).

Author: ajcvickers

AGENTS.md

@@ -34,7 +34,6 @@ The C# driver for MongoDB.
 | Feature area | Required environment variables |
 |---|---|
 | Atlas Search | `ATLAS_SEARCH_TESTS_ENABLED`, `ATLAS_SEARCH_URI` |
-| Atlas Search index helpers | `ATLAS_SEARCH_INDEX_HELPERS_TESTS_ENABLED`, `ATLAS_SEARCH_URI` |
 | CSFLE / auto-encryption | `CRYPT_SHARED_LIB_PATH` |
 | CSFLE with KMS mock servers | `KMS_MOCK_SERVERS_ENABLED` |
 | CSFLE with AWS KMS | `CSFLE_AWS_TEMPORARY_CREDS_ENABLED` |

docker-compose.atlas-local.yml

@@ -0,0 +1,33 @@
+# Atlas Local with Voyage AI auto-embedding enabled.
+#
+# The VOYAGE_API_KEY value is pulled from your shell environment at compose time.
+#
+#   export VOYAGE_API_KEY=...
+#   docker compose -f docker-compose.atlas-local.yml up -d
+#
+# To tear down (keeps the named volume so sample data + indexes survive):
+#   docker compose -f docker-compose.atlas-local.yml down
+#
+# To wipe everything including the data volume:
+#   docker compose -f docker-compose.atlas-local.yml down -v
+
+name: atlas-local-preview
+
+services:
+  mongodb:
+    image: mongodb/mongodb-atlas-local:preview
+    hostname: mongodb
+    container_name: local8g
+    environment:
+      - VOYAGE_API_KEY=${VOYAGE_API_KEY}
+    ports:
+      - 56661:27017
+    volumes:
+      - ./init:/docker-entrypoint-initdb.d
+      - db:/data/db
+      - configdb:/data/configdb
+      - mongot:/data/mongot
+volumes:
+  db:
+  configdb:
+  mongot:

evergreen/evergreen.yml

@@ -672,17 +672,6 @@ functions:
           . ${DRIVERS_TOOLS}/.evergreen/secrets_handling/setup-secrets.sh drivers/atlas-qa
           evergreen/run-atlas-search-test.sh
 
-  run-atlas-search-index-helpers-test:
-    - command: shell.exec
-      type: test
-      params:
-        working_dir: mongo-csharp-driver
-        include_expansions_in_env:
-          - "FRAMEWORK"
-        script: |
-          ${PREPARE_SHELL}
-          MONGODB_URI="${MONGODB_URI}" evergreen/run-atlas-search-index-helpers-test.sh
-
   run-ocsp-test:
     - command: shell.exec
       type: test
@@ -1383,13 +1372,6 @@ tasks:
             FRAMEWORK: net6.0
         - func: run-atlas-search-test
 
-    - name: atlas-search-index-helpers-test
-      commands:
-        - func: configure-framework
-          vars:
-            FRAMEWORK: net6.0
-        - func: run-atlas-search-index-helpers-test
-
     - name: test-oidc-auth
       commands:
         - func: configure-framework
@@ -2187,41 +2169,6 @@ task_groups:
     tasks:
       - test-csfle-with-gcp-kms
 
-  - name: atlas-search-index-helpers-task-group
-    setup_group_can_fail_task: true
-    setup_group_timeout_secs: 1800 # 30 minutes
-    setup_group:
-      - func: fetch-source
-      - func: prepare-resources
-      - func: fix-absolute-paths
-      - func: init-test-results
-      - func: make-files-executable
-      - func: assume-aws-test-secrets-role
-      - command: subprocess.exec
-        params:
-          binary: bash
-          include_expansions_in_env:
-            - "AWS_ACCESS_KEY_ID"
-            - "AWS_SECRET_ACCESS_KEY"
-            - "AWS_SESSION_TOKEN"
-          env:
-            CLUSTER_PREFIX: dbx-csharp-index
-            MONGODB_VERSION: "8.0"
-          args:
-            - ${DRIVERS_TOOLS}/.evergreen/atlas/setup-atlas-cluster.sh
-      - command: expansions.update
-        params:
-          file: atlas-expansion.yml
-    teardown_group:
-      - func: upload-test-results
-      - command: subprocess.exec
-        params:
-          binary: bash
-          args:
-            - ${DRIVERS_TOOLS}/.evergreen/atlas/teardown-atlas-cluster.sh
-    tasks:
-      - atlas-search-index-helpers-test
-
   - name: test-aws-lambda-task-group
     setup_group_can_fail_task: true
     setup_group_timeout_secs: 1800 # 30 minutes
@@ -2748,13 +2695,6 @@ buildvariants:
   tasks:
     - name: atlas-search-test
 
-- name: atlas-search-index-helpers-test
-  display_name: "Atlas Search Index Helpers Tests"
-  run_on:
-    - ubuntu2004-test
-  tasks:
-    - name: atlas-search-index-helpers-task-group
-
 # Socks5 Proxy tests
 - matrix_name: "socks5-proxy-tests-linux"
   matrix_spec: { os: "ubuntu-2004", ssl: ["nossl", "ssl"], version: ["latest"], topology: ["replicaset"] }

evergreen/run-atlas-search-index-helpers-test.sh

@@ -0,0 +1,25 @@
+/* Copyright 2010-present MongoDB Inc.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+using Xunit;
+
+namespace MongoDB.Driver.Tests.Search
+{
+    [CollectionDefinition(Name)]
+    public sealed class AtlasSearchCollection : ICollectionFixture<AtlasSearchFixture>
+    {
+        public const string Name = "AtlasSearch";
+    }
+}