Editing Tests

Having a thorough [https://en.wikipedia.org/wiki/Test_suite test suite] is something very important which is usually overlooked.  It is an incredible help in preventing regression bugs and quickly assess the status of old code.  For example, many packages in Octave Forge become deprecated after losing their maintainer simply because they have no test suite.

GNU Octave has multiple tools that help in creating a comprehensive test suite, accessible to both developers and end-users, as detailed on the [http://www.gnu.org/software/octave/doc/interpreter/Test-Functions.html Octave manual].  Basically, test blocks are {{codeline|%!test}} comment blocks, typically at the end of a source file, which are ignored by the Octave interpreter and only read by the {{manual|test}} function.

== Running tests ==

To run all the tests of a specific function, simply use the {{manual|test}} command at the Octave prompt.  For example, to run the tests of the Octave function {{manual|mean}} type:

 >> test mean
 PASSES 17 out of 17 tests

These tests are written in the Octave language [http://hg.savannah.gnu.org/hgweb/octave/file/6443693a176f/scripts/statistics/base/mean.m#l130 at the bottom of <code>mean.m</code>] which defines the {{manual|mean}} function.  It is important that these tests are also available for the end users so they can test the status of their installation.  The whole Octave test suite can be run with:

 >> __run_test_suite__
 
 Integrated test scripts:
 
 [...]
 
 Summary:
 
   PASS     11556
   FAIL         3
   XFAIL        6
   SKIPPED     38
 
 See the file test/fntests.log for additional details.

To run tests in a specific file, one can simply specify the path instead of a function name:

  test /full/path/to/file.m

== Writing tests ==

Tests appear as <code>%!</code> blocks at the bottom of the source file, together with <code>%!demo</code> blocks.  A typical m function file, will have the following structure:

<syntaxhighlight lang="Octave">
## Copyright
##
## A block with the copyright notice

## -*- texinfo -*-
##
## A block with the help text

function [x, y, z] = foo (bar)
  ## some amazing code
endfunction

%!assert (foo (1))
%!assert (foo (1:10))
%!assert (foo ("on"), "off")
%!error <must be positive integer> foo (-1)
%!error <must be positive integer> foo (1.5)

%!demo
%! ## see how cool foo() is:
%! foo([1:100])
</syntaxhighlight>

Tests can be added to oct functions in the C++ sources just as easily, see
[http://hg.savannah.gnu.org/hgweb/octave/file/f5ad7470d957/libinterp/corefcn/find.cc#l566 find.cc]
for example.  The syntax is exactly the same, but done within C comment blocks.
During installation, these lines are automatically extracted from the sources
and special test scripts are generated.  A typical C++ source file has the
following structure:

<syntaxhighlight lang="c++">
// Copyright
//
// A block with the copyright notice
 
DEFUN_DLD (foo, args, ,
"-*- texinfo -*-\n\
A block with the help text")
{
  // some amazing code
}
 
/*
%!assert (foo (1))
%!assert (foo (1:10))
%!assert (foo ("on"), "off")
%!error <must be positive integer> foo (-1)
%!error <must be positive integer> foo (1.5)
*/
</syntaxhighlight>

=== Assert ===

{{codeline|%!assert}} lines are the simplest one-line tests to write and also
the most common:

<syntaxhighlight lang="Octave">
%!assert (foo (bar))      # test fails if "foo (bar)" returns false
%!assert (foo (bar), qux) # test fails if "foo (bar)" is different from "qux"
</syntaxhighlight>

These are actually a shorthand version of
{{codeline|%!test assert (foo (bar))}}, and {{codeline|assert}} is simply
an Octave function that throws an error when two arguments fail to compare.

=== Error / Warning ===

It is also important to test that a function performs its checks correctly
and throws errors (or warnings) when it receives garbage.  This can be done with
{{codeline|error}} (or {{codeline|warning}}) blocks:

<syntaxhighlight lang="Octave">
%!error foo ()  # test that causes any error
%!error <BAR must be a positive integer> foo (-1.5)  # test that throws specific error message
%!error id=Octave:invalid-fun-call foo ()  # test that throws specific error id

%!warning foo ()  # test that causes any warning
%!warning <negative values might give inaccurate results> foo (-1.5)  # test that triggers a specific warning message
%!warning id=BAR:possibly-inaccurate-result foo (-1.5)  # test that triggers a specific warning id
</syntaxhighlight>

These are actually shorthand versions of 
{{codeline|%!test fail ("foo()", "error message")}} and {{codeline|%!test fail ("foo()", "warning", "warning message")}}, where {{codeline|%!fail}} returns true if the supplied code returns an error or warning.

=== Test Blocks===

While single {{codeline|%!assert}}, {{codeline|%!error}}, and {{codeline|%!warning}} lines are the most common used tests, {{codeline|%!test}} blocks offer more features and flexibility.  The code within {{codeline|%!test}} blocks is simply processed through the Octave interpreter.  If the code generates an error, the test is said to fail.  Often {{codeline|%!test}} blocks end with a call to {{codeline|assert}}:

<syntaxhighlight lang="Octave">
%!test
%! a = [0 1 0 0 3 0 0 5 0 2 1];
%! b = [2 5 8 10 11];
%! for i = 1:5
%!   assert (find (a, i), b(1:i))
%! endfor
</syntaxhighlight>

==== Test for no failure ====

In a few cases, there is the situation where a function returns nothing,
and the only thing to test is that it causes no error.  This can be tested
simply with:

<syntaxhighlight lang="Octave">
%!test foo (bar)
</syntaxhighlight>

==== Test for failure ====
If a warning or error message cannot be tested with one of the single-line tests mentioned above, the {{codeline|fail}} function can be used within a test block to verify expected error and warning functionality such as:

<syntaxhighlight lang="Octave">
%!test
%! a = [1 2 3];
%! b = [1 2];
%! fail ("a + b", "nonconformant arguments")

%!test
%! a = 111;
%! b = 112;
%! fail ("['foo', a, b]", "warning", "implicit conversion from numeric to char")
</syntaxhighlight>

The tests above pass if the errors/warnings occur as expected.

=== Shared functions ===

It is often useful to share a function among multiple tests.  Sometimes
these are only small helper functions, but more often these are just simpler
low performance implementations of the function being tested.  These are
created in {{codeline|%!function}} blocks:

<syntaxhighlight lang="Octave">
%!function x = slow_foo (bar)
%!  ## a simple implementation of foo, definitely correct, but
%!  ## unfortunately too slow for anything other than tests.
%!endfunction

%!assert (foo (bar), slow_foo (bar))

%!test
%! for i = -100:100
%!   bar = qux (i);
%!   assert (foo (bar), slow_foo (bar))
%! endfor
</syntaxhighlight>


[[Category:Testing]]
[[Category:Development]]