Assertion operators

[h2non]

• equal
• deep.equal
• strict.equal
• be
• be.true
• be.false
• be.none
• be.a / be.an / be.type
• be.empty
• be_above
• be.below
• be.above_or_equal
• be.below_or_equal
• be.within
• approximately
• be.callable
• have.len / have.length
• have.property
• have.properties
• have.key
• have.keys
• have.value
• have.values
• contain
• contain.exactly
• contain.only
• contain.deep
• startswith / start_with / starts_with
• endswith / end_with / ends_with
• match / matches
• match.each
• match.any
• raise_error / raises
• implements / satisfies
• first
• last
• head(size)
• tail(size)