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More about adding a collaboratorBuilt in matchers
Built-in Matchers
rspec-expectations ships with a number of built-in matchers.
Each matcher can be used with expect(..).to
or expect(..).not_to
to define
positive and negative expectations respectively on an object. Most matchers can
also be accessed using the (...).should
and (...).should_not
syntax, see
using should syntax
for why we recommend using expect
.
e.g.
expect(result).to eq(3)
expect(list).not_to be_empty
pi.should be > 3
Object identity
expect(actual).to be(expected) # passes if actual.equal?(expected)
Object equivalence
expect(actual).to eq(expected) # passes if actual == expected
Optional APIs for identity/equivalence
expect(actual).to eql(expected) # passes if actual.eql?(expected)
expect(actual).to equal(expected) # passes if actual.equal?(expected)
# NOTE: `expect` does not support `==` matcher.
Comparisons
expect(actual).to be > expected
expect(actual).to be >= expected
expect(actual).to be <= expected
expect(actual).to be < expected
expect(actual).to match(/expression/)
expect(actual).to be_within(delta).of(expected)
# NOTE: `expect` does not support `=~` matcher.
Types/classes
expect(actual).to be_instance_of(expected)
expect(actual).to be_kind_of(expected)
Truthiness and existentialism
expect(actual).to be_true # passes if actual is truthy (not nil or false)
expect(actual).to be_false # passes if actual is falsy (nil or false)
expect(actual).to be_nil # passes if actual is nil
expect(actual).to be # passes if actual is truthy (not nil or false)
Expecting errors
expect { ... }.to raise_error
expect { ... }.to raise_error(ErrorClass)
expect { ... }.to raise_error("message")
expect { ... }.to raise_error(ErrorClass, "message")
Expecting throws
expect { ... }.to throw_symbol
expect { ... }.to throw_symbol(:symbol)
expect { ... }.to throw_symbol(:symbol, 'value')
Predicate matchers
expect(actual).to be_xxx # passes if actual.xxx?
expect(actual).to have_xxx(:arg) # passes if actual.has_xxx?(:arg)
Examples
expect([]).to be_empty
expect(:a => 1).to have_key(:a)
Collection membership
expect(actual).to include(expected)
Examples
expect([1,2,3]).to include(1)
expect([1,2,3]).to include(1, 2)
expect(:a => 'b').to include(:a => 'b')
expect("this string").to include("is str")
Ranges (1.9 only)
expect(1..10).to cover(3)
Topics
- "be" matchers
- be_within matcher
- equality matchers
- exist matcher
- expect change
- raise_error matcher
- have(n).items matcher
- include matcher
- match matcher
- operator matchers
- predicate matchers
- respond_to matcher
- satisfy matcher
- throw_symbol matcher
- specify types of objects
- yield matchers
- cover matcher
- end_with matcher
- start_with matcher
Last published over 7 years ago by myronmarston.