Common Mistakes

High Level

Minimise logic in the controller (presentation logic in view, business logic in objects)
Avoid any redundancy - everything must have a purpose
Everything should be as simple as possible
attr_*
Avoid 'case' and 'elsif'
Use sessions or class instance variable in Sinatra but not both
Indent consistently
Beware vacuous tests
Stub out random behaviour
Correct use of expectations with Cucumber
Avoid unnecessary initialization

Cucumber/RSpec

Indent consistently +++
Avoid vacuous tests +
Ensure feature files are in feature directory, not support
Prefer more specific click_button or click_link to click_on
Prefer rspec expect syntax over should syntax
Separate out features correctly
Go for simple descriptions of tests
Stub out random behaviour
Avoid testing if something responds to a method
Ensure cucumber steps use correct variables
Leave expectations to cucumber Then blocks
stub out random behaviour
Instead of testing that it is not nil, you could give an array of possible values and check that it responds with one of those values.
Use before blocks to DRY out code
Prefer to not raise exceptions except for exceptional behaviour
Don't copy-paste
calling a unit test a feature test

Code

No need to initialize vars to nil or to empty hashes in other methods +++
Minimise logic in the controller +++
Looking up winning combination can be done through nested hash --> go to classes for Rock, Paper, Scissor? (either way avoid case statements or lots of elsif) +
Use the simplest code possible (i.e. avoid redundant code that does nothing) +
No presentation logic in controller or in business objects +
Remove anything that is not being used +
Avoid attr_accessor where possible, but use to shorten code where necessary +
Avoid combination of attr_reader and separate reader method
Use attr_* methods to DRY out code
Use sessions or global in Sinatra but not both
Avoid vacuous wrapper classes
Avoid adding objects to session - prefer ids due to restricted session space
Rescue specific errors, not general ones
Avoid get_ prefix on ruby methods
Prefer to use the private keyword once
Prefer to not raise exceptions except for exceptional behaviour
Don't copy-paste
font tags are evil
Avoid vacuous assignments def initialize; @name = name
Lower case for symbols
Avoid instance variables where unnecessary
Avoid assigning dummy vars to objects, i.e. no need to pass in a symbol when variable can be set later
Indent correctly

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