test: add mutation tests to reach 85%+ test efficacy

[CybotTM]

Summary

• Add 16 mutation test files targeting surviving mutants across cli, config, core, middlewares, and web packages
• Raises gremlins mutation test efficacy from 82.55% to 85.87% (1149 killed, 189 lived)
• Extract status string constants in doctor.go to satisfy goconst linter

Mutation Score Progress

Metric	Before	After	Change
Killed	1102	1149	+47
Lived	233	189	-44
Test efficacy	82.55%	85.87%	+3.32%

New Test Files

• cli/config_mutation_test.go
• cli/daemon_mutation_test.go
• cli/deprecations_mutation_test.go
• cli/docker_config_handler_mutation_test.go
• cli/doctor_mutation_test.go
• config/validator_mutation_test.go
• core/buffer_pool_mutation_test.go
• core/performance_metrics_mutation_test.go
• core/resilience_mutation_test.go
• core/retry_mutation_test.go
• core/scheduler_mutation_test.go
• middlewares/preset_mutation_test.go
• middlewares/slack_mutation_test.go
• middlewares/webhook_mutation_test.go
• web/middleware_mutation_test.go
• web/server_mutation_test.go

Test plan

• All go test ./... -tags='!e2e' pass
• golangci-lint passes
• Gremlins mutation testing confirms 85.87% efficacy

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[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None

[github-actions]

Automated approval for solo maintainer project

All CI checks passed. See SECURITY.md for compensating controls.

[github-actions]

⚠️ Mutation Testing Results

Mutation Score: 50.00% (threshold: 60%)

⚠️ Score is below threshold. Consider improving test coverage or test quality.

What is mutation testing?

Mutation testing measures test quality by introducing small changes (mutations) to the code and checking if tests detect them. A higher score means better test effectiveness.

• Killed mutants: Tests caught the mutation (good!)
• Survived mutants: Tests missed the mutation (needs improvement)

[Copilot]

Pull request overview

This pull request adds comprehensive mutation tests to increase test efficacy from 82.55% to 85.87%, killing 44 additional mutants. The changes include 16 new mutation test files targeting surviving mutants across cli, config, core, middlewares, and web packages. Additionally, status string constants are extracted in doctor.go to satisfy the goconst linter.

Changes:

• Add 16 mutation test files targeting boundary conditions, conditional negations, arithmetic operations, and increment/decrement mutations
• Extract status string constants ("pass", "fail", "skip") in doctor.go for code quality
• Update test files to use the new status constants

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
cli/doctor.go	Extract status constants (statusPass, statusFail, statusSkip) to satisfy goconst linter
cli/doctor_test.go	Update tests to use new status constants
web/server_mutation_test.go	Tests for token expiry, UI filesystem mounting, job type reflection, and HTTP timeouts
web/middleware_mutation_test.go	Tests for rate limiter cleanup boundaries, window calculations, and IP extraction
middlewares/webhook_mutation_test.go	Tests for webhook retry logic, attempt counting, sleep timing, and trigger filtering
middlewares/slack_mutation_test.go	Tests for Slack HTTP client initialization, error handling, and message formatting
middlewares/preset_mutation_test.go	Tests for preset validation, method defaults, content-type handling, and URL building
core/scheduler_mutation_test.go	Tests for scheduler initialization, job management, workflow cleanup, and concurrency limits
core/retry_mutation_test.go	Tests for retry attempt boundaries, delay calculations, and exponential backoff
core/resilience_mutation_test.go	Tests for circuit breaker transitions, rate limiter refills, and bulkhead counters
core/performance_metrics_mutation_test.go	Tests for metrics boundary conditions, counter increments, and rate calculations
core/buffer_pool_mutation_test.go	Tests for buffer pool operations (not shown in diff)
cli/docker_config_handler_mutation_test.go	Tests for Docker configuration resolution, container filtering, and error handling
cli/deprecations_mutation_test.go	Tests for deprecation detection in webhooks, config keys, and migration logic
cli/daemon_mutation_test.go	Tests for daemon option application, config defaults, and timeout values
cli/config_mutation_test.go	Tests for config operations (not shown in diff)

[github-actions]

🚀 Released in v0.20.0

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This is now available in the latest release. Please test and verify everything works as expected in your environment.

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