[test] Add tests for config.fetchAndFixSchema transformations and launcher.cleanupIdleConnections closed state

[github-actions]

Test Coverage Improvement: fetchAndFixSchema + cleanupIdleConnections

Functions Analyzed

Package	Function	Uncovered Branches
internal/config	fetchAndFixSchema	3 schema-transformation blocks (lines 121–193), invalid-JSON path (lines 113–115)
internal/launcher	cleanupIdleConnections	ConnectionStateClosed removal branch (lines 146–149)

Why These Functions?

fetchAndFixSchema is the most complex untested function found: it applies three distinct schema-transformation blocks to work around JSON Schema Draft 7 limitations (negative-lookahead patterns, registry/guard-policies injection). All existing tests use simple mock schemas that lack the customServerConfig, customSchemas.patternProperties, and stdioServerConfig/httpServerConfig structures required to exercise those branches. This means a large portion of the function's logic ran 0 times under test.

cleanupIdleConnections had tests for idle-timeout and error-count removal, but not the third trigger: a connection that is already in ConnectionStateClosed state. That branch (lines 146–149) was unreachable by the existing pool tests.

Tests Added

internal/config/fetch_and_fix_schema_test.go (new file, 10 test functions)

• ✅ TestFetchAndFixSchema_InvalidJSONResponse — server returns malformed JSON → failed to parse schema error
• ✅ TestFetchAndFixSchema_TransformCustomServerConfigType — negative-lookahead pattern removed, not: {enum: ["stdio","http"]} injected
• ✅ TestFetchAndFixSchema_CustomServerConfigType_MissingSubStructures — transformation is a no-op when definitions, customServerConfig, properties, or type key is absent
• ✅ TestFetchAndFixSchema_TransformCustomSchemasPatternProperties — (?!…) key replaced with ^[a-z][a-z0-9-]*$; original value preserved
• ✅ TestFetchAndFixSchema_CustomSchemasPatternProperties_NoNegativeLookahead — existing simple key left untouched when no negative-lookahead is present
• ✅ TestFetchAndFixSchema_AddRegistryAndGuardPoliciesToStdioConfig — registry (string, with description) and guard-policies (object, additionalProperties: true) injected into stdioServerConfig.properties
• ✅ TestFetchAndFixSchema_AddRegistryAndGuardPoliciesToHttpConfig — same injection into httpServerConfig.properties; pre-existing url field preserved
• ✅ TestFetchAndFixSchema_RegistryGuardPolicies_MissingSubStructures — injection is a no-op when properties key is absent in either config
• ✅ TestFetchAndFixSchema_AllTransformationsApplied — schema with all triggering structures validates all three transformations end-to-end
• ✅ TestFetchAndFixSchema_PreservesSchemaIntegrity — pre-existing fields (container, args, required) survive the transformation pass unchanged

internal/launcher/connection_pool_test.go (2 new functions)

• ✅ TestCleanupIdleConnections_AlreadyClosedState — connection manually set to ConnectionStateClosed (recently used, 0 errors) is removed on next cleanup pass
• ✅ TestCleanupIdleConnections_ClosedConnectionSkipsDoubleClose — idle + already-closed connection exercises both the idle-timeout and the closed-state branches; verifies the inner State != ConnectionStateClosed guard prevents a redundant state mutation

Coverage Estimate

fetchAndFixSchema (transformation branches):   0% → ~95%
cleanupIdleConnections (closed-state branch):  ~67% → ~100%

Test Design Notes

• schemaServer helper avoids calling t.FailNow() / require inside the HTTP handler goroutine (uses t.Errorf instead) — safe for all Go versions
• All fetchAndFixSchema tests verify round-tripped JSON (marshal → unmarshal) to ensure transformations survive the full JSON lifecycle
• Pool tests use direct pool.mu.Lock() / pool.connections[key] = &ConnectionMetadata{...} to inject ConnectionStateClosed state that no public API can produce, matching the package launcher white-box test pattern used throughout the file

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Generated by Test Coverage Improver — next candidates: mcp.initializeHTTPSession non-200/RPC-error branches, config.validateStandardServerConfig HTTP-with-mounts path

Generated by Test Coverage Improver · ◷

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[Copilot]

Pull request overview

Adds targeted unit tests to cover previously untested branches in schema-fetch transformation logic (internal/config.fetchAndFixSchema) and connection pool cleanup behavior (internal/launcher.cleanupIdleConnections), improving confidence in these edge paths.

Changes:

• Add a new internal/config test suite covering malformed JSON handling and all three schema transformation blocks in fetchAndFixSchema.
• Extend internal/launcher connection pool tests to cover removal of connections already in ConnectionStateClosed.
• Add helper utilities to serve and re-unmarshal schemas for transformation assertions.

Reviewed changes

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

File	Description
internal/launcher/connection_pool_test.go	Adds tests for cleanup behavior when a pooled connection is already marked closed.
internal/config/fetch_and_fix_schema_test.go	New tests covering schema fetch parsing error path and all schema transformation branches.

Comments suppressed due to low confidence (1)

internal/launcher/connection_pool_test.go:460

• This test also depends on the periodic cleanup goroutine and fixed sleeps. It can be made more reliable by calling pool.cleanupIdleConnections() directly (since this is a white-box test in package launcher) instead of sleeping, which avoids timing/scheduler variance in CI.

func TestCleanupIdleConnections_ClosedConnectionSkipsDoubleClose(t *testing.T) {
	ctx := context.Background()
	config := PoolConfig{
		IdleTimeout:     10 * time.Millisecond,
		CleanupInterval: 20 * time.Millisecond,
		MaxErrorCount:   100,
	}
	pool := NewSessionConnectionPoolWithConfig(ctx, config)
	defer pool.Stop()

	// Insert a connection that is both idle AND already closed.
	// The cleanup should remove it via the "already closed" path without
	// attempting to close it again.
	key := ConnectionKey{BackendID: "backend2", SessionID: "session2"}
	pool.mu.Lock()
	pool.connections[key] = &ConnectionMetadata{
		Connection: &mcp.Connection{},
		CreatedAt:  time.Now().Add(-1 * time.Hour),
		LastUsedAt: time.Now().Add(-1 * time.Hour), // idle for a long time
		ErrorCount: 0,
		State:      ConnectionStateClosed,
	}
	pool.mu.Unlock()

	require.Equal(t, 1, pool.Size())

	// Wait for cleanup.
	time.Sleep(60 * time.Millisecond)

	assert.Equal(t, 0, pool.Size(),
		"idle+closed connection should be cleaned up exactly once")
}

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