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More about adding a collaboratorspecify types of objects
rspec-expectations includes two matchers to specify types of objects:
- obj.should be_kind_of(type): calls obj.kind_of?(type), which returns true if type is in obj's class hierarchy or is a module and is included in a class in obj's class hierarchy.
- obj.should be_instance_of(type): calls obj.instance_of?(type), which returns true if and only if type if obj's class.
Both of these matchers have aliases:
- obj.should be_a_kind_of(type) # same as obj.should be_kind_of(type)
- obj.should be_a(type) # same as obj.should be_kind_of(type)
- obj.should be_an(type) # same as obj.should be_kind_of(type)
- obj.should be_an_instance_of(type) # same as obj.should be_instance_of(type)
- Scenarios
-
- be_(a_)kind_of matcher
-
- Given
-
a file named "be_kind_of_matcher_spec.rb" with:
module MyModule; end class Fixnum include MyModule end describe 17 do # the actual class it { should be_kind_of(Fixnum) } it { should be_a_kind_of(Fixnum) } it { should be_a(Fixnum) } # the superclass it { should be_kind_of(Integer) } it { should be_a_kind_of(Integer) } it { should be_an(Integer) } # an included module it { should be_kind_of(MyModule) } it { should be_a_kind_of(MyModule) } it { should be_a(MyModule) } # negative passing case it { should_not be_kind_of(String) } it { should_not be_a_kind_of(String) } it { should_not be_a(String) } # deliberate failures it { should_not be_kind_of(Fixnum) } it { should_not be_a_kind_of(Fixnum) } it { should_not be_a(Fixnum) } it { should_not be_kind_of(Integer) } it { should_not be_a_kind_of(Integer) } it { should_not be_an(Integer) } it { should_not be_kind_of(MyModule) } it { should_not be_a_kind_of(MyModule) } it { should_not be_a(MyModule) } it { should be_kind_of(String) } it { should be_a_kind_of(String) } it { should be_a(String) } end
- When
-
I run
rspec be_kind_of_matcher_spec.rb
- Then
-
the output should contain all of these:
24 examples, 12 failures expected 17 not to be a kind of Fixnum expected 17 not to be a kind of Integer expected 17 not to be a kind of MyModule expected 17 to be a kind of String
- be_(an_)instance_of matcher
-
- Given
-
a file named "be_instance_of_matcher_spec.rb" with:
module MyModule; end class Fixnum include MyModule end describe 17 do # the actual class it { should be_instance_of(Fixnum) } it { should be_an_instance_of(Fixnum) } # the superclass it { should_not be_instance_of(Integer) } it { should_not be_an_instance_of(Integer) } # an included module it { should_not be_instance_of(MyModule) } it { should_not be_an_instance_of(MyModule) } # another class with no relation to the subject's hierarchy it { should_not be_instance_of(String) } it { should_not be_an_instance_of(String) } # deliberate failures it { should_not be_instance_of(Fixnum) } it { should_not be_an_instance_of(Fixnum) } it { should be_instance_of(Integer) } it { should be_an_instance_of(Integer) } it { should be_instance_of(MyModule) } it { should be_an_instance_of(MyModule) } it { should be_instance_of(String) } it { should be_an_instance_of(String) } end
- When
-
I run
rspec be_instance_of_matcher_spec.rb
- Then
-
the output should contain all of these:
16 examples, 8 failures expected 17 not to be an instance of Fixnum expected 17 to be an instance of Integer expected 17 to be an instance of MyModule expected 17 to be an instance of String
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