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List: ruby-talk
Subject: assertions in Ruby
From: "Volkmann, Mark" <Mark.Volkmann () AGEDWARDS ! com>
Date: 2002-10-04 13:43:46
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Is anyone aware of a Ruby module that adds support for assertions such as
what is supported in Java 1.4? I wrote such a thing yesterday and am
considering releasing it if I'm not duplicating what someone else has
already done.
I've included some examples below showing how mine is used.
When an assertion fails, a stack trace is output, a message describing the
failed assertion is output and execution stops (actually it raises an
AssertionError which typically would not be caught). This is primarily for
use during initial development of new code. Assertions are disabled by
default. To enable them, the global variable $enable_assertions must be set
to true (Should I use some other mechanism besides a global variable to do
this?). Even when assertions are disabled, they provide good documentation
on what your code expects.
---
require 'Assertions'
$enable_assertions = true
# Assert that the value of temperature is in the range 0 to 100.
# The first parameter is the condition to be tested (should evaluate to true
or false)
# and the last parameter is a description of what is being asserted.
assert((0..100).include?(temperature), "valid temperature returned")
# Assert that the object wsdl responds to the messages "proxy" and
"service".
# The first parameter is the value to be tested and the remaining parameters
# are any number of symbols referring to messages.
assert_responds(wsdl, :proxy, :service)
# Assert that the object currently referred to by operationName is a kind of
String.
# The first parameter is the value to be tested and the
# remaining parameters are the allowed types for the value.
assert_type(operationName, String, QName)
# Assert that localName is a kind of String, namespace is a kind of String
and
# prefix is either a kind of String or is nil.
# Each parameter is an array containing a value to be tested
# and the types allowed for that value.
# NilClass is used to specify that a value can be nil.
assert_types([localName, String],
[namespace, String],
[prefix, String, NilClass])
I understand all the debate over whether checking types in Ruby code is a
good idea. Even if you decide not to use assert_responds, assert_type and
assert_types, using just the assert method to test certain conditions is
useful on its own.
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<P><FONT SIZE=2>Is anyone aware of a Ruby module that adds support for assertions \
such as what is supported in Java 1.4? I wrote such a thing yesterday and am \
considering releasing it if I'm not duplicating what someone else has already \
done.</FONT></P>
<P><FONT SIZE=2>I've included some examples below showing how mine is used.</FONT>
</P>
<P><FONT SIZE=2>When an assertion fails, a stack trace is output, a message \
describing the failed assertion is output and execution stops (actually it raises an \
AssertionError which typically would not be caught). This is primarily for use \
during initial development of new code. Assertions are disabled by \
default. To enable them, the global variable $enable_assertions must be set to \
true (Should I use some other mechanism besides a global variable to do this?). \
Even when assertions are disabled, they provide good documentation on what your code \
expects.</FONT></P>
<P><FONT SIZE=2>---</FONT>
</P>
<P><FONT SIZE=2>require 'Assertions'</FONT>
</P>
<P><FONT SIZE=2>$enable_assertions = true</FONT>
</P>
<P><FONT SIZE=2># Assert that the value of temperature is in the range 0 to \
100.</FONT> <BR><FONT SIZE=2># The first parameter is the condition to be tested \
(should evaluate to true or false)</FONT> <BR><FONT SIZE=2># and the last parameter \
is a description of what is being asserted.</FONT> <BR><FONT \
SIZE=2>assert((0..100).include?(temperature), "valid temperature \
returned")</FONT> </P>
<P><FONT SIZE=2># Assert that the object wsdl responds to the messages \
"proxy" and "service".</FONT> <BR><FONT SIZE=2># The first \
parameter is the value to be tested and the remaining parameters</FONT> <BR><FONT \
SIZE=2># are any number of symbols referring to messages.</FONT> <BR><FONT \
SIZE=2>assert_responds(wsdl, :proxy, :service) </FONT> </P>
<P><FONT SIZE=2># Assert that the object currently referred to by operationName is a \
kind of String.</FONT> <BR><FONT SIZE=2># The first parameter is the value to be \
tested and the</FONT> <BR><FONT SIZE=2># remaining parameters are the allowed types \
for the value.</FONT> <BR><FONT SIZE=2>assert_type(operationName, String, \
QName)</FONT> </P>
<P><FONT SIZE=2># Assert that localName is a kind of String, namespace is a kind of \
String and</FONT> <BR><FONT SIZE=2># prefix is either a kind of String or is \
nil.</FONT> <BR><FONT SIZE=2># Each parameter is an array containing a value to be \
tested</FONT> <BR><FONT SIZE=2># and the types allowed for that value.</FONT>
<BR><FONT SIZE=2># NilClass is used to specify that a value can be nil.</FONT>
<BR><FONT SIZE=2>assert_types([localName, String],</FONT>
<BR><FONT SIZE=2> \
[namespace, String],</FONT> <BR><FONT \
SIZE=2> \
[prefix, String, NilClass])</FONT> </P>
<P><FONT SIZE=2>I understand all the debate over whether checking types in Ruby code \
is a good idea. Even if you decide not to use assert_responds, assert_type and \
assert_types, using just the assert method to test certain conditions is useful on \
its own.</FONT></P>
<CODE><FONT SIZE=3><BR>
<BR>
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otherwise recorded by the A.G. Edwards corporate e-mail system and is<BR>
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