Test that something gives a true value
assert "code that evaluates to true"
Test that something is nil
assert_nil "code that evaluates to nil"
Test that something is empty
assert_empty "code that evaluates to something that is empty"
Test that something is the same as something else
assert_equal "expected result", "code that evaluates to the result"
Test that something is an instance of a particular class
assert_instance_of "class", "code that evaluates to an object"
Test that something is a kind of a particular class
assert_kind_of "class", "code that evaluates to an object"