CSHARP-5930: Update replica-set discovery and reporting in tests

[ajcvickers]

See CSHARP-6008 for details about why this change is needed.

There were multiple iterations getting to this point:

Iteration 1

RequireServer.cs

• ClusterType()/ClusterTypes(): Now use GetActualClusterType() which maps a directConnect RS member to ClusterType.ReplicaSet (instead of the misleading Standalone)
• topology/topologies case: Uses actual server type — single matches only Standalone, replicaset matches IsReplicaSetMember()

DriverTestConfiguration.cs

• IsReplicaSet(): Checks server.Type.IsReplicaSetMember() instead of cluster.Description.Type == ClusterType.ReplicaSet, so a directConnect RS is correctly identified

ReadPreferenceOnStandaloneTests.cs (from earlier)

• Uses ServerType.Standalone instead of ClusterType.Standalone to decide whether $readPreference is expected

ServerDiscoveryProseTests.cs

• Missing secondary now throws SkipException instead of a plain Exception

UnifiedTestSpecRunner.cs

• Added IsDirectConnectionToReplicaSet() helper
• ServerDiscoveryAndMonitoring: Skips logging-replicaset.json, replicaset-emit-topology-changed-before-close.json, rediscover-quickly-after-step-down.json when on directConnect RS (these require full multi-server topology discovery events)
• ServerSelection: Skips replica-set.json when on directConnect RS (same reason)

Iteration 2

• Root cause: My GetActualClusterType() change made RequireServer.ClusterType(ClusterType.ReplicaSet) pass for a directConnect RSPrimary. This caused Connection_pool_should_not_be_cleared_when_replSetStepDown_and_GetMore to run — a test that was previously always skipped on this setup. That test calls { replSetStepDown: 30, force: true }, which makes the single-node RS step down and refuse writes for up to 30 seconds. All subsequent write operations in other tests (like DropCollection in fixture setup) then fail with MongoNotPrimaryException.
• Fix: Added RequireServer.ReplicaSetDataBearingMembers(int minimum) — a new check that counts how many data-bearing RS members the cluster has

Iteration 3

• Applied .ReplicaSetDataBearingMembers(2) to Connection_pool_should_not_be_cleared_when_replSetStepDown_and_GetMore — the step-down test only makes sense (and is safe) with at least 2 RS members so a new primary can be elected after the step-down

Iteration 4

• CausalConsistencyExamples.cs — Causal_Consistency_Example_3: Replaced the hardcoded "mongodb://localhost/?readPreference=secondaryPreferred" with settings built from CoreTestConfiguration.ConnectionString plus ReadPreference.SecondaryPreferred. The example intent is preserved.
• ClientSideEncryption2Examples.cs — FLE2AutomaticEncryption: Added an explicit skip when CRYPT_SHARED_LIB_PATH is not set (CSFLE/auto-encryption requires it), and fixed two new MongoClient() calls to use CoreTestConfiguration.ConnectionString.ToString() instead of the default localhost:27017.

[Copilot]

Pull request overview

Updates test infrastructure to correctly identify replica-set topology and adjust spec/prose tests behavior when running against direct connections to replica-set members (especially single-node RS), preventing unsafe/invalid test executions and improving environment-dependent skipping.

Changes:

• Refines cluster/topology detection in test helpers to treat directConnection replica-set members as replica-set (based on server type), and adds a ReplicaSetDataBearingMembers(min) requirement.
• Updates unified spec runner and SDAM prose tests to skip cases that require full replica-set topology discovery (or a secondary) when the environment can’t provide it.
• Makes examples use CoreTestConfiguration.ConnectionString instead of hardcoded localhost URIs and adds an explicit skip for CSFLE2 auto-encryption when CRYPT_SHARED_LIB_PATH is missing.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/MongoDB.Driver.Tests/Specifications/server-discovery-and-monitoring/prose-tests/ServerDiscoveryProseTests.cs	Skips SDAM prose test when no secondary is available.
tests/MongoDB.Driver.Tests/Specifications/UnifiedTestSpecRunner.cs	Adds direct-connect-to-RS detection and skips unified spec cases requiring full RS discovery events.
tests/MongoDB.Driver.Tests/ConnectionsSurvivePrimaryStepDownTests.cs	Ensures the replSetStepDown test only runs when >=2 data-bearing members exist.
tests/MongoDB.Driver.TestHelpers/DriverTestConfiguration.cs	Detects replica-set via server types (works with direct connect).
tests/MongoDB.Driver.TestHelpers/Core/XunitExtensions/RequireServer.cs	Uses effective cluster type for direct connections; adds RS member-count requirement; updates runOn topology matching to use server type.
tests/MongoDB.Driver.Examples/ClientSideEncryption2Examples.cs	Skips CSFLE2 auto-encryption without crypt_shared lib; uses test connection string for clients.
tests/MongoDB.Driver.Examples/CausalConsistencyExamples.cs	Uses test connection string + ReadPreference.SecondaryPreferred via settings rather than hardcoded localhost URI.

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.