RSpec's should style to expect style

should_to_expect.rb

obj.should ...
expect(obj).to ...

obj.should_not ...
expect(obj).not_to ...

obj.should =~ //
expect(obj).to match(//)

[1, 2, 3].should =~ [3, 2, 1]
expect([1, 2, 3]).to match_array([3, 2, 1])

obj.should > 3
expect(obj).to be > 3

lambda { ... }.should raise_error
expect { ... }.to raise_error

# RSpec 2.14.0 or later

obj.stub(:foo)
allow(obj).to receive(:foo)

SomeClass.any_instance.should_receive(:foo)
expect_any_instance_of(SomeClass).to receive(:foo)

SomeClass.any_instance.stub(:foo)
allow_any_instance_of(SomeClass).to receive(:foo)