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about_exceptions.rb
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about_exceptions.rb
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require File.expand_path(File.dirname(__FILE__) + '/edgecase')
class AboutExceptions < EdgeCase::Koan
class MySpecialError < RuntimeError
end
def test_exceptions_inherit_from_Exception
assert_equal __(RuntimeError), MySpecialError.ancestors[1]
assert_equal __(StandardError), MySpecialError.ancestors[2]
assert_equal __(Exception), MySpecialError.ancestors[3]
assert_equal __(Object), MySpecialError.ancestors[4]
end
def test_rescue_clause
result = nil
begin
fail "Oops"
rescue StandardError => ex
result = :exception_handled
end
assert_equal __(:exception_handled), result
assert ex.is_a?(___(StandardError)), "Failure message."
assert ex.is_a?(___(RuntimeError)), "Failure message."
assert RuntimeError.ancestors.include?(StandardError), # __
"RuntimeError is a subclass of StandardError"
assert_equal __("Oops"), ex.message
end
def test_raising_a_particular_error
result = nil
begin
# 'raise' and 'fail' are synonyms
raise MySpecialError, "My Message"
rescue MySpecialError => ex
result = :exception_handled
end
assert_equal __(:exception_handled), result
assert_equal __("My Message"), ex.message
end
def test_ensure_clause
result = nil
begin
fail "Oops"
rescue StandardError => ex
# no code here
ensure
result = :always_run
end
assert_equal __(:always_run), result
end
# Sometimes, we must know about the unknown
def test_asserting_an_error_is_raised # __
# A do-end is a block, a topic to explore more later
assert_raise(___(MySpecialError)) do
raise MySpecialError.new("New instances can be raised directly.")
end
end
end