rspec-1.3.2 | rspec-rails-1.3.4

Method Stubs

A method stub is an implementation of a method that returns a canned response.

The main difference between a method stub and a message expectation is that message expectations verify interactions that you expect, while method stubs just sit there and return values.

Setting an explicit return value

This is the simplest (and recommended) approach to stubbing.

my_instance.stub!(:msg).and_return(value)
MyClass.stub!(:msg).and_return(value)

Calculating a return value

my_instance.stub!(:msg).and_return { ... }
MyClass.stub!(:msg).and_return { ... }

While this is possible, it is generally to be avoided. Calculating a value to return defeats the declarative nature of stubs.

Multiple return values

my_instance.stub!(:msg).and_return("1",2)
MyClass.stub!(:msg).and_return("1",2)

This will return “1” the first time it is called and 2 every subsequent call. Like calculated return values, this is a little un-stubby, but it can be a handy feature once in a while.

Mixing method stubs and message expectations

In some cases it can be helpful to stub a default return value, but set a message expectation for a specific set of args. For example:

A.stub!(:msg).and_return(:default_value)
A.should_receive(:msg).with(:arg).and_return(:special_value)
A.msg
=> :default_value
A.msg(:any_other_arg)
=> :default_value
A.msg(:arg)
=> :special_value
A.msg(:any_other_other_arg)
=> :default_value
A.msg
=> :default_value