Capybara matchers can be applied to standalone HTML fragments or strings, not only full pages, making fragment assertions easier in test suites.

Create ZIP archives in Ruby with zipruby; add existing files, string buffers, and directories using Ruby bindings for libzip.

Serving files as downloads in Ruby on Rails uses send_file; it returns the file directly and overrides the normal render response.

Keep the cursor on its row while scrolling a Vim buffer, avoiding jumps to the top or bottom of the screen. Default keys move the viewport by a line or half screen.

Sets Thunderbird archive folder date formatting and folder granularity for year and month subfolders, and can modify the A shortcut with Shift, Control, or Alt.

Run Selenium tests in a hidden X session with vncserver, keeping the browser accessible for inspection without adding a gem.

Passenger can start a Rails app in the wrong environment unless Apache is configured with the correct RailsEnv or RackEnv setting.

Firefox 3.6 print output cuts off long tables, often due to CSS floats, overflow rules, or nearby h1 and caption tags.

Hidden X displays can be inspected by taking a screenshot of the active display, including Xvfb-backed sessions used for headless tests.

Rough JavaScript equivalent of Rails simple_format for turning plain text into HTML paragraphs and line breaks. Whitespace preservation is not included.

Manual queue processing in Resque specs avoids relying on an external worker while keeping behavior close to real job execution.

Resque dashboard access can bypass ApplicationController filters in Rails 3, so a Rack middleware can protect it with Clearance and a remember token.

Ruby 1.9 upgrades in Rails apps often fail because of gem incompatibilities, lambda arity issues, and encoding mismatches between files, strings, and databases.

File.chmod sets Unix file permissions in Ruby, where the leading zero matters for octal mode values.

Inactive users are logged out after a period without requests, using Clearance cookie expiration and a per-request refresh to keep active sessions alive.

Temporary downloads can fail in Rails 3 when send_file triggers X-Sendfile and the web server cannot read files under /tmp. Using an allowed temp directory avoids 404 errors.

Typing accented letters on dead-key-free keyboard layouts is still possible with a configured Compose key and the right compose combinations.

Rails 3 remote links can replace page content with returned HTML, restoring the Rails 2 link_to_remote update behavior through jQuery and rails-ujs.

Selenium and Launchy can trigger Firefox profile errors when Launchy opens pages through the active browser. Setting LAUNCHY_BROWSER and BROWSER to Chrome or another browser avoids the conflict.

any_instance stubbing and expectations now work in RSpec 2.6, enabling should_receive and stub on instances created inside code.

Exception tracking service for any platform with a Rails notifier and REST API, useful as a free alternative to Hoptoad/Airbrake for custom error reporting.

Hex values for the 16-color CGA palette used on Color Graphics Adapter displays in the 1980s.

Virtual date attributes in forms arrive as strings, so Rails does not auto-cast them like database columns. A custom accessor can coerce them to Date objects or nil.