Constant resolution in Ruby can be surprising when names are missing or resolved in an unexpected scope. Understanding lookup rules helps diagnose NameError and visibility issues.

Sass functions must return values; a computed line left unassigned or unreturned triggers @function rules may not contain style rules because Sass does not mutate objects.

Chrome DevTools can pause code when browser events fire, making it easier to trace where clicks and other handlers are processed.

DOM breakpoints in Chrome DevTools or Firefox Inspector help trace JavaScript that changes an element’s subtree, attributes, or removes it.

Configure .rspec to load spec_helper or rails_helper automatically, avoiding repeated require lines in every spec and making parallel test setups work with .rspec_parallel.

evaluate_script can freeze a browser window for about 10 seconds when it returns complex JavaScript objects; execute_script avoids the costly result conversion.

A Git alias can push a branch to GitLab and create a draft merge request automatically, with an optional target branch override.

Chrome DevTools can store a selected DOM element as a global variable for quick inspection and reuse in the console.

Overriding initialize in ActiveType::Object can break ActiveRecord-style setup, freeze instances, or cause argument errors unless super is called with one attribute hash.

Bundler can fail to fetch gems from rubygems.org when IPv6 connectivity is broken. Lowering IPv6 priority in /etc/gai.conf can let bundle install succeed temporarily.

Flaky integration tests can outrun watchInputDelay, causing Unpoly field updates to overwrite typed input before requests start. Lowering the delay or signaling CapybaraLockstep reduces failures.

Rails 7+ validates dates, numbers and strings with ComparisonValidator for greater-than and less-than checks, replacing custom comparison code.

Strong Parameters for CarrierWave uploads need more than the file field; cache and removal flags keep images across validation errors and enable deletion.

Safer branch navigation in Git benefits from git switch, a clearer alternative to git checkout for changing, creating, and detaching branches.

Finds large files and directories consuming disk space on servers or minimal systems with a text-based interface.

MySQL treats 0 = 'any string' as true, so mixed string-integer comparisons can match unexpected rows and bypass indexes; PostgreSQL rejects such comparisons.

wkhtmltopdf can fail with ProtocolUnknownError when file:// URLs are blocked by default, preventing local assets such as stylesheets from loading.

robots.txt can block crawling without removing URLs from search results, while noindex removes accessible pages from indexing. Disallowed URLs may still appear as search matches.

Unique scratch directories prevent flaky tests and stale files in parallel Ruby test runs. Dir.mktmpdir creates them safely and can use a custom base path.

Recover the change history of a deleted file in Git by using git log with history-preserving flags across all references.