test(core): add unit tests for normalizeHeaders and createFetchWithInit

[k61b]

Add unit tests for normalizeHeaders and createFetchWithInit in packages/core/src/shared/transport.ts.

Motivation and Context

These utility functions are used by both SSEClientTransport and StreamableHTTPClientTransport but had no dedicated unit tests. Adding coverage helps catch regressions and documents expected behavior.

How Has This Been Tested?

pnpm -C packages/core test
# 441 tests passed

Breaking Changes

None. Test-only change.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

(This is a test-only change)

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

Tests cover:

• normalizeHeaders: undefined, Headers instance, array of tuples, plain objects
• createFetchWithInit: base init passthrough, option merging, header merging precedence

[changeset-bot]

⚠️ No Changeset found

Latest commit: 87ce712

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commit: 87ce712

[Copilot]

Pull request overview

This PR adds comprehensive unit tests for two utility functions (normalizeHeaders and createFetchWithInit) in the transport module that previously lacked dedicated test coverage. The tests verify various input formats for header normalization and proper merging behavior for fetch initialization options.

Key changes:

• New test file with 142 lines covering two utility functions
• Tests for normalizeHeaders validate handling of undefined, Headers instances, arrays of tuples, and plain objects
• Tests for createFetchWithInit verify base initialization passthrough, option merging, and header merging precedence

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[felixweinberger]

@claude review

[claude]

LGTM, straightforward test-only addition for existing utility functions.

Extended reasoning...

Overview

This PR adds a single new test file (packages/core/test/shared/transport.test.ts) with unit tests for normalizeHeaders and createFetchWithInit — two utility functions exported from packages/core/src/shared/transport.ts. No production code is modified.

Security risks

None. This is a test-only change that adds no production code, no new dependencies, and no changes to any runtime behavior.

Level of scrutiny

Low scrutiny warranted. This is a new test file covering existing, stable utility functions. The tests correctly exercise the implementation's code paths: undefined/Headers/array/object normalization, baseInit passthrough, option merging with call-time override precedence, and header merge behavior. The author addressed all Copilot review suggestions (adding empty-init and Headers-passthrough test cases) with reasonable justifications.

Other factors

• All existing tests pass per the PR description (441 tests).
• No changeset needed since this is test-only.
• The test patterns (vi.fn globals, describe/test structure) are consistent with the project's vitest configuration (globals: true).

[felixweinberger]

Seems fine to add, thanks!