Expand unit tests

[github-actions]

Cover all flag combinations in processEvent, error branches in runCodex, edge cases in parseEnvInput/parseListInput, and add/modify/delete workflows in detectChanges.

[YiweiShen]

/codex --full-history Please go through the codebase, check if there is anything we can improve, and create the PR.

[github-actions]

Created Pull Request: #355