Fetch a remote server’s TLS certificate in Ruby without sending a full request. The certificate can be inspected, cached as PEM, and reloaded with OpenSSL::X509::Certificate.

Imported Sass files need a leading underscore or they compile into standalone CSS and can fail when they depend on shared variables or mixins.

Extracting a backtrace from a running Ruby process helps diagnose hangs and crashes without waiting for a restart. gdb can attach live or inspect a core file.

Capistrano 2 provides shell and invoke for running tasks or ad hoc commands on deployment targets, with support for individual hosts and roles.

Ruby string encodings can behave unexpectedly and trigger invalid byte sequence errors in UTF-8 when text is handled with the wrong encoding.

Capybara multi-session tests support simultaneous users in browser-based chat flows, but session-aware authentication state is needed to avoid conflicts.

Rails API backends can be fast and easy to extend, but serializer maintenance, schema drift, documentation limits, and missing rate limits create real operational risks.

JSONB columns can hold dynamic attributes in ActiveRecord, but validation and strict defaults are easy to lose. JSON Schema keeps evolving hashes predictable.

Duplicate links in Capybara can trigger Ambiguous match errors when any matching link is fine; switching Capybara.match to :first avoids the failure.

Capybara fill_in can raise Capybara::Ambiguous when visible field labels overlap. match: :prefer_exact or a global exact matching strategy avoids substring conflicts.

Verify that a value was created by a specific constructor in Jasmine with jasmine.any(Klass) instead of direct instance checks.

SQL mode mismatches can break apps after MySQL or MariaDB upgrades by changing strictness, grouping rules, and allowed values.

Rails applications can send mail through Gmail’s SMTP server with smtp_settings; Google app passwords enable delivery when two-factor authentication is enabled.

Large SQL queries become hard to maintain as joins, subqueries, and filters pile up. PostgreSQL views and materialized views can encapsulate that complexity in Ruby on Rails.

Bundler 2 introduced compatibility issues and confusing behavior, with further changes after release. Upgrading can break dependency management and require a migration path.

Ubuntu's ibus emoji picker can conflict with existing shortcuts such as Ctrl+Shift+E, especially in terminal apps. The binding can be removed in ibus-setup.

jQuery done() and then() differ in promise chaining: then() waits for returned promises, while done() ignores them and can resolve too early.

Quickly serve a local folder for testing, or boot a Rack app, with one-line commands in Ruby, Python, Passenger, or Puma; HTTPS is possible too.

Shared RSpec examples can be rerun by --example substring match or example ID when rspec file:line cannot target them directly.

RSpec 3 can raise undefined method 'describe' for main:Object when DSL methods are not exposed globally; disable_monkey_patching! turns them off, and expose_dsl_globally = true restores them.

A Linux server with a performance issue needs fast triage in the first minute. Core commands reveal load, memory, CPU, disk, network, and process bottlenecks.

SVG icons stay crisp only when their viewBox grid matches the rendered size; odd scaling triggers antialiasing, blur, and thicker strokes.