Add vNext emulator pipeline with Gateway mode support

[TheovanKraay]

Pull Request Template

Description

This PR adds CI/CD pipeline support for the vNext emulator (preview), enabling automated validation of the .NET SDK against the next-generation Azure Cosmos DB emulator.

Key Changes

Pipeline Configuration:

• Added azure-pipelines-vnext-emulator.yml - Daily scheduled pipeline (2 AM UTC) for vNext emulator validation
• Added templates/emulator-vnext-setup.yml - Template for vNext emulator setup
• Pipeline runs independently and does NOT block PRs (validation only)

vNext Emulator Support:

• HTTP Protocol Support: Added COSMOSDBEMULATOR_ENDPOINT environment variable support to override default HTTPS endpoint
  • vNext emulator uses HTTP (http://localhost:8081/) instead of HTTPS
  • Maintains backward compatibility with legacy emulator (HTTPS via settings.json)
• Gateway Mode Enforcement: Added AZURE_COSMOS_EMULATOR_CONNECTION_MODE environment variable
  • Forces all tests to use Gateway mode (vNext limitation - no Direct mode support)
  • Applied across all test creation methods in TestCommon.cs

Test Infrastructure Updates:

• Modified ConfigurationManager.cs: Environment variable now overrides settings.json for endpoint configuration
• Updated TestCommon.cs: All CreateCollectionAsync methods respect Gateway mode environment variable
• Added throughput capping (≤10000 RU/s) when in Gateway mode to accommodate vNext single-partition limitation
• Updated QueryTests.cs and RoutingGatewayCosmosItemIdEncodingTests.cs for vNext compatibility

Test Results (Initial Validation)

Overall: 36 tests passing out of 225 tested (16% pass rate)

Category	Passed	Total	Pass Rate
ChangeFeed	21	61	34.4%
ClientTelemetryEmulator	8	21	38.1%
Query	4	78	5.1%
Batch	2	50	4.0%
ReadFeed	1	15	6.7%

Excluded Tests: MultiPartition and CrossPartition tests excluded due to vNext single-partition constraint

vNext Emulator Limitations

The vNext emulator has significant differences from the legacy emulator:

• Protocol: HTTP only (no HTTPS/SSL)
• Connection Mode: Gateway only (no Direct mode)
• Partitioning: Single partition containers only
• Feature Set: Limited compared to legacy emulator (explains low pass rates)

Trigger Options

• Daily Schedule: Runs automatically at 2 AM UTC
• Manual: Via Azure Pipelines UI
• PR Comment: /azp run vnext-emulator (for on-demand testing)

Backward Compatibility

✅ All changes maintain full backward compatibility:

• Legacy emulator tests unchanged (use HTTPS from settings.json by default)
• vNext emulator tests use environment variable override (opt-in)
• No breaking changes to existing test infrastructure
• Regular PR validation unaffected

Documentation

Comprehensive documentation available in OneDrive:
C:\Users\thvankra\OneDrive - Microsoft\cosmos-db-pm\sdk\vnext SDK\vNext-SDK-Test-Status.md

Includes:

• Complete test results breakdown
• How to run vNext tests locally
• Known limitations and issues
• Improvement roadmap
• Risk assessment

Type of change

• New feature (non-breaking change which adds functionality)

Closing issues

N/A - This adds new vNext emulator validation infrastructure without closing specific issues.