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* Testing
Testing is an important part of the Mono project: every one of its
three major components has a test suite tailored for its needs. This
is very helpful, because in the course of developing the software it
is very common to introduce bugs in existing code. A test suite
helps us fix the bugs as soon as they are introduced.
** Class Library Tests
All classes in Mono libraries should have comprehensive unit test
suites to go with them. Unit testing is a software engineering
methodology that makes it easier to build correct code. Every
method in every class should have a set of tests to verify
that they work correctly. Mono also needs a testing framework
to make it easy to write and run lots of tests.
** Getting started
If you are new to writing NUnit tests, there is a template you may use
to help get started. The file is:
<b>mcs/class/doc/TemplateTest.cs</b>
Save a copy of this file in the appropriate test subdirecty
(see below), and replace all the {text} markers with
appropriate code. Comments in the template are there to guide
you. You should also look at existing tests to see how other
people have written them.
mcs/class/corlib/Test/System.Collections/CollectionBaseTest.cs
is a small one that might help.
The directory that will contain your new file depends on the
assembly/namespace of the class for which you are creating the
tests. Under mcs/class there is a directory for each
assembly. In each assembly there is a Test directory,
e.g. mcs/class/corlib/Test. In the Test directory there are
sub-directories for each namespace in the assembly,
e.g. mcs/class/corlib/Test/Sytem. Put your new test file in
the appropriate sub-directory under Test for the class you are
testing.
Once all of that is done, you can do a 'make test' from the top mcs
directory. Your test class will be automagically included in the
build and the tests will be run along with all the others.
* Tips on writing Unit tests.
You should look at the <a href="http://nunit.org">NUnit documentation</a>,
as it is a fantastic product, and includes fantastic documentation,
but here are some tips for those of you who are already reading
this web page.
** Provide an unique error message for Assert()
Include an unique message for each Assert() so that when the assert
fails, it is trivial to locate it in the source. Otherwise, it may be
difficult to determine which part of the test is failing. A good way
to ensure unique messages is to use something like #A01, #A02 etc.
Ok:
<pre>
AssertEquals("array match", compare[0], i1[0]);
AssertEquals("array match", compare[1], i1[1]);
AssertEquals("array match", compare[2], i1[2]);
AssertEquals("array match", compare[3], i1[3]);
</pre>
Excellent:
<pre>
AssertEquals("#A01", compare[0], i1[0]);
AssertEquals("#A02", compare[1], i1[1]);
AssertEquals("#A03", compare[2], i1[2]);
AssertEquals("#A04", compare[3], i1[3]);
</pre>
Once you used such a number in an Assert(), don't change it later on -
people might use it it identify the test in bug reports or in mailing
lists.
** Use AssertEquals() to compare things, not Assert().
Do not compare two values with Assert() - if the test fails,
people have no idea what went wrong while AssertEquals()
reports the failed value.
Ok:
<pre>
Assert ("A01", myTicks[0] == t1.Ticks);
</pre>
Excellent:
<pre>
AssertEquals ("A01", myTicks[0], t1.Ticks);
</pre>
** Test your test with the Microsoft runtime
If possible, try to run your testsuite with the Microsoft runtime on
.NET on Windows and make sure all tests in it pass. This is especially
important if you're writing a totally new testcase - without this
check you can never be sure that your testcase contains no bugs ....
Don't worry if you're writing your test on Linux, other people can
test it for you on Windows.
Sometimes you may discover that a test doesn't show the expected
result when run with the Microsoft runtime - either because there is a
bug in their runtime or something is misleading or wrong in their
documentation. In this case, please put a detailed description of the
problem to mcs/class/doc/API-notes and do also report it to the
<a href="mailing-lists">mailing list</a> - we'll forward this to the
Microsoft people from time to time to help them fix their documentation
and runtime.
** Unit tests.
Why do unit testing? It becomes simple to run automated tests
for the whole library. Unit tests are a safety net - you can
change part of the code and verify that you haven't broken
anything. Ideally, tests are written before the actual library
code itself. And every time a bug is discovered, a test should
be written to demonstrate the bug and its fix. Then, if
you ever reintroduce the bug, you will know immediately. For
more info, read <a
href="http://junit.sourceforge.net/doc/testinfected/testing.htm">
JUnit Test Infected: Programmers Love Writing Tests</a>.
** Getting Started
We welcome all contributions to the Class Libary Test Suite.
There is information to help you get started in CVS at
mcs/class/doc/NUnitGuidelines. Once you have written your test, please
post it to <a href="mailing-lists.html">mono-list</a>.
Someone will make sure to add the file or apply the patch as
appropriate. If you plan to be an on-going contributor and
would like to get cvs account, email <a href="mailto:miguel@ximian.com">miguel</a>.
Normally, after you send a couple of well-written new files
and/or patches to the list, you will be given cvs access.
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