test: add comprehensive test coverage for MCP allowHeadless feature

[continue-development-app]

Overview

This PR adds comprehensive test coverage for the allowHeadless feature introduced in PR #9328. The new tests ensure robust behavior of MCP tools in headless mode across various scenarios.

Test Coverage Added

1. Edge Cases and Error Handling

• Disconnected MCP servers
• Empty connections array
• MCP server with empty tools array
• Explicit allowHeadless: false behavior

2. Permission Policy Interactions

• Wildcard exclude policies vs allowHeadless
• Specific allow vs wildcard ask policies
• allowHeadless with wildcard ask policy
• Wildcard ask without allowHeadless in headless mode
• argumentMatches with allowHeadless

3. Integration Tests

• Mixed built-in and MCP tools in headless mode
• Tool order preservation when filtering
• Interactive to headless mode transition

4. Built-in Tool Behavior

• Built-in tools work in headless mode regardless of allowHeadless flag

Key Improvements

1. Comprehensive edge case coverage: Tests error conditions and boundary cases
2. Permission policy interactions: Validates complex policy scenarios with wildcards
3. Integration testing: Ensures components work together correctly
4. Real-world scenarios: Tests common use cases like multiple mixed servers
5. Security validation: Explicitly tests that security policies cannot be bypassed

Security-Critical Tests

✅ Explicit exclusions always respected (cannot be bypassed by allowHeadless)
✅ Wildcard excludes take precedence over allowHeadless
✅ Default behavior is secure (tools excluded without explicit allowHeadless: true)

Test Organization

Tests are organized into 4 logical groups:

• MCP tools in headless mode (original tests from PR docs: add allowHeadless documentation for MCP servers in CLI headless mode #9328)
• MCP tool execution permission in headless mode (original + new built-in test)
• MCP tool edge cases and error handling (new)
• MCP tool permission policy interactions (new)
• MCP tool integration tests (new)

Files Modified

• extensions/cli/src/stream/mcp-headless.test.ts: Added 12 new test cases
• TEST_IMPROVEMENTS.md: Documentation of test improvements

Test Statistics

• Original tests: 9 test cases
• New tests: 12 test cases
• Total coverage: 21 test cases

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This task was co-authored by peter-parker and Continue.

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Summary by cubic

Added 12 tests that verify MCP allowHeadless behavior in headless mode. Improves security guarantees and covers real-world scenarios.

• Test Coverage
  • Edge cases: disconnected servers, empty connections/tools, explicit allowHeadless: false.
  • Policies: wildcard exclude precedence, wildcard ask with/without allowHeadless, argumentMatches.
  • Integration: mixed built-in + MCP tools, order preservation, interactive→headless transition.
  • Built-in tools: always approved in headless mode.

^{Written for commit 981c13f. Summary will update automatically on new commits.}

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[cubic-dev-ai]

No issues found across 4 files

[RomneyDa]

Likely will not have allowHeadless option