Test::Unit : assert_aborts

[Stephan Wehner]

Is there an existing way to assert that abort is invoked with
Test::Unit. Here's what I came up with.

Place in "test_helper.rb" for example.

------------------------------------------------------
# Three redefinitions to be able to assert aborts.
class AbortException < Exception
end

class Test::Unit::TestCase
def assert_aborts(msg_or_pattern)
asserted = false
caught_exception = 'none'
begin
yield if block_given? # if there is no block, there will not be
any abort
either
rescue AbortException => e
caught_exception = e
if msg_or_pattern.is_a? String
assert_equal msg_or_pattern, e.to_s.sub(/^[a-z_]*: /,'')
return
end
if msg_or_pattern.is_a? Regexp
assert_match msg_or_pattern, e.to_s
return
end
end
flunk "Expected to handle abort with >>#{ msg_or_pattern }<<. Caught
exception >>#{ caught_exception }<< but didn't handle"
end
end

module Kernel
def abort(msg)
raise AbortException.new(msg)
end
end
------------------------------------------------------

Then in a test

def test_aborting
assert_aborts 'fatal error encountered' do
trigger_abort # ....
end
end




Stephan

 

[Brian Candler]

Have you tried

assert_raises(AbortException) { ... }

?

 

[Stephan Wehner]

Have you tried

assert_raises(AbortException) { ... }

?

Thanks -- if you are suggesting to leave out the method assert_aborts: I
thought it might be good to check the abort message. Otherwise, please
let me know.

Stephan

 

[Daniel Berger]

-----Original Message-----
From: (e-mail address removed) [mailto:[email protected]]
Sent: Sunday, May 24, 2009 3:44 AM
To: ruby-talk ML
Subject: Re: Test::Unit : assert_aborts

Have you tried

assert_raises(AbortException) { ... }

?

Thanks -- if you are suggesting to leave out the method assert_aborts:
I
thought it might be good to check the abort message. Otherwise, please
let me know.

See assert_raise_message in Test::Unit 2.x.

gem install test-unit

Regards,

Dan

 

[Stephan Wehner]

See assert_raise_message in Test::Unit 2.x.

gem install test-unit

Regards,

Dan

Ok thanks. Should I submit patches to Ruby?

1. assert_aborts through redefining Kernel#abort
2. assert_raise_message accepts regular expression.

Stephan

 

[James Gray]

Thanks -- if you are suggesting to leave out the method
assert_aborts: I
thought it might be good to check the abort message. Otherwise, please
let me know.

It's possible to check the message even in old versions of
Test::Unit. For example:

class SpecificError < RuntimeError; end

require "test/unit"

class TestErrorHandling < Test::Unit::TestCase
def test_error_type_and_message
error = assert_raise(SpecificError) do
raise SpecificError, "Magic message goes here..."
end
assert_match(/magic/i, error.message)
end
end

__END__

As for testing for abort(), I wouldn't. What are you really trying to
figure out, if the code would exit with an error message? Then check
that. Throw a StringIO in $stderr and check for a message and see if
Ruby is planning to exit. abort() raises the same Exception exit
does, so just check for that:

require "test/unit"

class TestErrorHandling < Test::Unit::TestCase
def test_error_type_and_message
assert_raise(SystemExit) do
abort "Bye."
end
end
end

__END__

Hope that helps.

James Edward Gray II

 

[Stephan Wehner]

It's possible to check the message even in old versions of
Test::Unit. For example:

class SpecificError < RuntimeError; end

require "test/unit"

class TestErrorHandling < Test::Unit::TestCase
def test_error_type_and_message
error = assert_raise(SpecificError) do
raise SpecificError, "Magic message goes here..."
end
assert_match(/magic/i, error.message)
end
end

__END__

As for testing for abort(), I wouldn't. What are you really trying to
figure out, if the code would exit with an error message? Then check
that. Throw a StringIO in $stderr and check for a message and see if
Ruby is planning to exit. abort() raises the same Exception exit
does, so just check for that:

require "test/unit"

class TestErrorHandling < Test::Unit::TestCase
def test_error_type_and_message
assert_raise(SystemExit) do
abort "Bye."
end
end
end

__END__

Hope that helps.

Ok, thanks a lot!

You mean something like this.


require "test/unit"
require 'stringio'

class TestErrorHandling < Test::Unit::TestCase
def test_error_type_and_message_II
assert_aborts(/bye/i) do
abort "Bye."
end
end

private

def assert_aborts(pattern)
save_stderr = $stderr
begin
$stderr = StringIO.new
e = assert_raise(SystemExit) do
yield if block_given?
end
assert_match pattern, e.message
ensure
$stderr=save_stderr
end
end
end

__END__


Stephan

 

[James Gray]

You mean something like this.


require "test/unit"
require 'stringio'

class TestErrorHandling < Test::Unit::TestCase
def test_error_type_and_message_II
assert_aborts(/bye/i) do
abort "Bye."
end
end

private

def assert_aborts(pattern)
save_stderr = $stderr
begin
$stderr = StringIO.new
e = assert_raise(SystemExit) do
yield if block_given?
end
assert_match pattern, e.message
ensure
$stderr=save_stderr
end
end
end

__END__

Sort of like that, yeah. Basically what I was saying is that I feel
an assert_aborts() method tests an implementation detail.

It doesn't really matter if I use abort() or some output method and
then call exit() myself. There may be good reasons to do that too,
say if you are printing a complex error message and using printf()
would make it easier to format.

We really just want to know if the user saw an error and if the
program is quitting, so it's better to test for that.

James Edward Gray II

 

[Stephan Wehner]

Sort of like that, yeah. Basically what I was saying is that I feel
an assert_aborts() method tests an implementation detail.

It doesn't really matter if I use abort() or some output method and
then call exit() myself. There may be good reasons to do that too,
say if you are printing a complex error message and using printf()
would make it easier to format.

We really just want to know if the user saw an error and if the
program is quitting, so it's better to test for that.

Ok, thanks a lot; that makes sense.

Stephan

 

[Eric Hodel]

class Test::Unit::TestCase
def assert_aborts(msg_or_pattern)
asserted = false
caught_exception = 'none'
begin
yield if block_given? # if there is no block, there will not be
any abort
either
rescue AbortException => e
caught_exception = e
if msg_or_pattern.is_a? String
assert_equal msg_or_pattern, e.to_s.sub(/^[a-z_]*: /,'')
return
end
if msg_or_pattern.is_a? Regexp
assert_match msg_or_pattern, e.to_s
return
end
end
flunk "Expected to handle abort with >>#{ msg_or_pattern }<<.
Caught
exception >>#{ caught_exception }<< but didn't handle"
end
end

module Kernel
def abort(msg)
raise AbortException.new(msg)
end
end

You're doing far, far too much work!

$ ruby -rstringio -e '$stderr = StringIO.new; begin; abort "hi";
rescue Exception; p $!; end'
#<SystemExit: hi>

Capturing $stderr (then ignoring it) and checking if SystemExit is
raised and has the right message is enough:

$ cat test.rb
require 'minitest/autorun'

class TestA < MiniTest::Unit::TestCase
def assert_aborts(message)
e = assert_raises SystemExit do
capture_io do
yield
end
end

assert_equal message, e.message
end

def test_a
assert_aborts "hi" do
abort "hi"
end
end
end
$ ruby19 test.rb
Loaded suite test
Started