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# 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](https://github.com/rspec/rspec-expectations/blob/master/Should.md)
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)
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