[Feature]: Support TEST_RUNNER_ prefixed env vars

[eastlondoner]

Feature Description

If I have my MCP server set up with a TEST_RUNNER_ prefixed env var it should be passed through to xcodebuild test commands as an env var.

TEST_RUNNER_ prefix is documented here:
https://developer.apple.com/documentation/xcode/environment-variable-reference

Using this example MCP config

{
  "mcpServers": {
    "XcodeBuildMCP": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "xcodebuildmcp@latest"],
      "env": {
        "TEST_RUNNER_USE_DEV_MODE": "YES"
      }
    }
  }
}

Then I should be able to run a UI test like this:

  func testFoo() throws {
    // Check configuration requirement
    let useDevMode = ProcessInfo.processInfo.environment["runsForEachTargetApplicationUIConfiguration"] == "YES"
    guard useDevMode else {
      XCTFail("Test requires USE_DEV_MODE to be true")
      return
    }

Alternatively the test tools should have a parameter for setting env vars.

Use Cases

This allows me to conditionally disable the runsForEachTargetApplicationUIConfiguration property to speed up dev tests.

Example Interactions

No response

[cameroncooke]

Implementation Complete ✅

I have implemented TEST_RUNNER_ environment variable support as requested in this issue. The solution is available in PR #102.

Implementation Summary

Approach: Explicit parameter-based solution with automatic TEST_RUNNER_ prefix handling

Key Features:

• ✅ New testRunnerEnv parameter on all test tools (test_device, test_sim, test_macos)
• ✅ Automatic TEST_RUNNER_ prefix handling via normalizeTestRunnerEnv() utility
• ✅ Leverages xcodebuild built-in TEST_RUNNER_ environment variable passthrough
• ✅ Comprehensive test coverage (26 new tests)
• ✅ Security-focused design with explicit parameters

Rationale for Explicit Parameter Approach

While the original issue suggested environment variable detection, I implemented an explicit parameter approach for security and architectural reasons:

1. Security: Prevents injection attacks and unintended environment variable leakage
2. Principle of Least Privilege: Only explicitly provided variables are passed to test processes
3. MCP Architecture Alignment: MCP server environment variables are for the server itself, not downstream tools
4. Clarity: Makes variable passing explicit and intentional rather than implicit

Usage Example

# Via Reloaderoo CLI
npx reloaderoo inspect call-tool test_sim --params '{
  "projectPath": "/path/to/project.xcodeproj",
  "scheme": "MyScheme",
  "simulatorName": "iPhone 16",
  "testRunnerEnv": { "USE_DEV_MODE": "YES", "API_ENDPOINT": "staging" }
}' -- node build/index.js

The tool automatically converts { USE_DEV_MODE: "YES" } to { TEST_RUNNER_USE_DEV_MODE: "YES" } and passes it to xcodebuild, which strips the prefix and provides USE_DEV_MODE=YES to the test runner.

Validation

• ✅ All existing tests pass (1087 tests)
• ✅ Manual testing with UI tests confirms functionality works
• ✅ Both success and failure cases validated
• ✅ All quality checks pass (build, lint, typecheck)

This solution addresses the core need while providing a secure, maintainable foundation for environment variable passing in test workflows.

[cameroncooke]

@eastlondoner let me know if this works for you:
npm i https://pkg.pr.new/cameroncooke/XcodeBuildMCP/xcodebuildmcp@102

[cameroncooke]

@eastlondoner thanks again for the suggestion, will release it shortly.