Custom empty? on a has_many model can break Machinist collection building, creating records with the wrong foreign key. Use explicit association assignment instead.

cucumber.yml may be valid while rerun.txt is corrupted by parallel Cucumber workers writing at the same time, preventing Cucumber from starting.

RSpec 1.x can leave stubbed class methods in place between examples, causing order-dependent failures when spec file evaluation changes.

Run one Cucumber feature file directly with script/cucumber, or invoke it through rake when speed is less important.

Jasmine describe() throws AfterAll TypeError: Failed to execute 'appendChild' on 'Node' when an object is passed instead of a string.

Finds a record by any string or number across columns, making Cucumber step definitions more flexible. The bang variant raises ActiveRecord::NotFound when nothing matches.

Cucumber can fail with little or no visible error output; a backtrace, verbose formatter, or debug mode can expose the underlying cause.

Network failures between a host and a single target can be isolated with ping checks and an automatic mtr report by email.

Cucumber failures can open the current page in a browser automatically, avoiding repeated "Then show me the page" reruns and speeding up debugging.

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

Nested patiently blocks now wait independently in Spreewald, preventing detached DOM failures when with_scope reuses cached elements.

patently blocks must keep local variables inside the block; rebinding an outer variable breaks retries because later attempts reuse the changed value.

Selenium can miss browser events such as change during form input; a Cucumber step can fire jQuery-registered events manually with execute_script.

Association values in Machinist blueprints need blocks so Project.make runs per blueprint instance, not once at parse time when RSpec loads.

Lazy let evaluation keeps RSpec examples shorter when a setup call has many required arguments, and lets stubs change the result before the value is used.

VCR integration with Cucumber 4 breaks when use_scenario_name: true is enabled, causing an undefined feature method error in Cucumber::RunningTestCase::TestCase.

Capybara find can return incorrect matches when called on nodes from all, especially with text filters. Use a full selector on the page to scope the search reliably.

Run multiple example or scenario line numbers from one file with rspec or cucumber, using colon-separated targets instead of separate commands.

Run Sidekiq jobs synchronously in development to avoid a separate worker process and benefit from code reloading.

Rails JSON serializes times with milliseconds, so iso8601 and to_json can differ in RSpec expectations. Using to_json keeps time string comparisons matching.

BEM-style selectors can be generated from plain-language Cucumber locators, reducing repetitive typing when mapping readable step text to CSS classes.

Cucumber docstrings break when nested triple double quotes appear inside the text; escaping or a Transform can preserve embedded quote markers.

Cucumber factory now infers the model class from the factory, so steps can use natural names like admin instead of user (admin).

Clicking elements by raw CSS selector is brittle; selector_for lets feature steps use plain English names like sidebar instead.