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@node Test and Demo Functions
@appendix Test and Demo Functions
@cindex test functions

Octave includes a number of functions to allow the integration of testing
and demonstration code in the source code of the functions themselves.

@menu
* Test Functions::
* Demonstration Functions::
@end menu

@node Test Functions
@section Test Functions

@DOCSTRING(test)

@code{test} scans the named script file looking for lines which start
with the identifier @samp{%!}.  The prefix is stripped off and the rest
of the line is processed through the Octave interpreter.  If the code
generates an error, then the test is said to fail.

Since @code{eval()} will stop at the first error it encounters, you must
divide your tests up into blocks, with anything in a separate
block evaluated separately.  Blocks are introduced by valid keywords like
@code{test}, @code{function}, or @code{assert} immediately following @samp{%!}.
A block is defined by indentation as in Python.  Lines beginning with
@samp{%!<whitespace>} are part of the preceding block.

For example:

@example
@group
%!test error ("this test fails!")
%!test "test doesn't fail.  it doesn't generate an error"
@end group
@end example

When a test fails, you will see something like:

@example
@group
  ***** test error ("this test fails!")
!!!!! test failed
this test fails!
@end group
@end example

Generally, to test if something works, you want to assert that it
produces a correct value.  A real test might look something like

@example
@group
%!test
%! @var{a} = [1, 2, 3; 4, 5, 6]; B = [1; 2];
%! expect = [ @var{a} ; 2*@var{a} ];
%! get = kron (@var{b}, @var{a});
%! if (any (size (expect) != size (get)))
%!   error ("wrong size: expected %d,%d but got %d,%d",
%!          size (expect), size (get));
%! elseif (any (any (expect != get)))
%!   error ("didn't get what was expected.");
%! endif
@end group
@end example

To make the process easier, use the @code{assert} function.  For example,
with @code{assert} the previous test is reduced to:

@example
@group
%!test
%! @var{a} = [1, 2, 3; 4, 5, 6]; @var{b} = [1; 2];
%! assert (kron (@var{b}, @var{a}), [ @var{a}; 2*@var{a} ]);
@end group
@end example

@code{assert} can accept a tolerance so that you can compare results
absolutely or relatively.  For example, the following all succeed:

@example
@group
%!test assert (1+eps, 1, 2*eps)           # absolute error
%!test assert (100+100*eps, 100, -2*eps)  # relative error
@end group
@end example

You can also do the comparison yourself, but still have assert
generate the error:

@example
@group
%!test assert (isempty ([]))
%!test assert ([1, 2; 3, 4] > 0)
@end group
@end example

Because @code{assert} is so frequently used alone in a test block, there
is a shorthand form:

@example
%!assert (@dots{})
@end example

@noindent
which is equivalent to:

@example
%!test assert (@dots{})
@end example

Occasionally a block of tests will depend on having optional
functionality in Octave.  Before testing such blocks the availability of
the required functionality must be checked.  A @code{%!testif HAVE_XXX}
block will only be run if Octave was compiled with functionality
@samp{HAVE_XXX}.  For example, the sparse single value decomposition,
@code{svds()}, depends on having the @sc{arpack} library.  All of the tests
for @code{svds} begin with

@example
%!testif HAVE_ARPACK
@end example

@noindent
Review @file{config.h} or @code{__octave_config_info__ ("build_features")}
to see some of the possible values to check.

Sometimes during development there is a test that should work but is
known to fail.  You still want to leave the test in because when the
final code is ready the test should pass, but you may not be able to
fix it immediately.  To avoid unnecessary bug reports for these known
failures, mark the block with @code{xtest} rather than @code{test}:

@example
@group
%!xtest assert (1==0)
%!xtest fail ("success=1", "error")
@end group
@end example

@noindent
In this case, the test will run and any failure will be reported.
However, testing is not aborted and subsequent test blocks will be
processed normally.  Another use of @code{xtest} is for statistical
tests which should pass most of the time but are known to fail
occasionally.

Each block is evaluated in its own function environment, which means
that variables defined in one block are not automatically shared
with other blocks.  If you do want to share variables, then you
must declare them as @code{shared} before you use them.  For example, the
following declares the variable @var{a}, gives it an initial value (default
is empty), and then uses it in several subsequent tests.

@example
@group
%!shared @var{a}
%! @var{a} = [1, 2, 3; 4, 5, 6];
%!assert (kron ([1; 2], @var{a}), [ @var{a}; 2*@var{a} ])
%!assert (kron ([1, 2], @var{a}), [ @var{a}, 2*@var{a} ])
%!assert (kron ([1,2; 3,4], @var{a}), [ @var{a},2*@var{a}; 3*@var{a},4*@var{a} ])
@end group
@end example

You can share several variables at the same time:

@example
%!shared @var{a}, @var{b}
@end example

Modifications to shared variables persist from one test to the next
@strong{only} if the test succeeds.  Thus, if one test modifies a shared
variable, later tests cannot know which value of the shared variable to expect
because the pass/fail status of earlier tests is unknown.  For this reason, it
is not recommended to modify shared variables in tests.

You can also share test functions:

@example
@group
%!function @var{a} = fn (@var{b})
%!  @var{a} = 2*@var{b};
%!endfunction
%!assert (fn(2), 4)
@end group
@end example

Note that all previous variables and values are lost when a new
shared block is declared.

Remember that @code{%!function} begins a new block and that
@code{%!endfunction} ends this block.  Be aware that until a new block
is started, lines starting with @samp{%!<space>} will be discarded as comments.
The following is nearly identical to the example above, but does nothing.

@example
@group
%!function @var{a} = fn (@var{b})
%!  @var{a} = 2*@var{b};
%!endfunction
%! assert (fn(2), 4)
@end group
@end example

@noindent
Because there is a space after @samp{%!} the @code{assert} statement does
not begin a new block and this line is treated as a comment.

Error and warning blocks are like test blocks, but they only succeed
if the code generates an error.  You can check the text of the error
is correct using an optional regular expression @code{<pattern>}.
For example:

@example
%!error <passes!> error ("this test passes!")
@end example

If the code doesn't generate an error, the test fails.  For example:

@example
%!error "this is an error because it succeeds."
@end example

@noindent
produces

@example
@group
  ***** error "this is an error because it succeeds."
!!!!! test failed: no error
@end group
@end example

It is important to automate the tests as much as possible, however
some tests require user interaction.  These can be isolated into
demo blocks, which if you are in batch mode, are only run when
called with @code{demo} or the @code{verbose} option to @code{test}.
The code is displayed before it is executed.  For example,

@example
@group
%!demo
%! @var{t} = [0:0.01:2*pi]; @var{x} = sin (@var{t});
%! plot (@var{t}, @var{x});
%! # you should now see a sine wave in your figure window
@end group
@end example

@noindent
produces

@example
@group
funcname example 1:
 @var{t} = [0:0.01:2*pi]; @var{x} = sin (@var{t});
 plot (@var{t}, @var{x});
 # you should now see a sine wave in your figure window

Press <enter> to continue:
@end group
@end example

Note that demo blocks cannot use any shared variables.  This is so
that they can be executed by themselves, ignoring all other tests.

If you want to temporarily disable a test block, put @code{#} in place
of the block type.  This creates a comment block which is echoed
in the log file but not executed.  For example:

@example
@group
%!#demo
%! @var{t} = [0:0.01:2*pi]; @var{x} = sin (@var{t});
%! plot (@var{t}, @var{x});
%! # you should now see a sine wave in your figure window
@end group
@end example

@noindent
The following trivial code snippet provides examples for the use of
fail, assert, error, and xtest:

@example
@group
function @var{output} = must_be_zero (@var{input})
  if (@var{input} != 0)
    error ("Nonzero input!")
  endif
  @var{output} = @var{input};
endfunction

%!fail ("must_be_zero (1)")
%!assert (must_be_zero (0), 0)
%!error <Nonzero> must_be_zero (1)
%!xtest error ("This code generates an error")
@end group
@end example

@noindent
When putting this in a file @file{must_be_zero.m}, and running the test, we see

@example
@group
test must_be_zero verbose

@result{}
>>>>> /path/to/must_be_zero.m
***** fail ("must_be_zero (1)")
***** assert (must_be_zero (0), 0)
***** error <Nonzero> must_be_zero (1)
***** xtest error ("This code generates an error")
!!!!! known failure
This code generates an error
PASSES 3 out of 4 tests (1 expected failure)
@end group
@end example

@subsubheading Block type summary:

@table @code
@item  %!test
@itemx %!test <MESSAGE>
Check that entire block is correct.  If @code{<MESSAGE>} is present, the
test block is interpreted as for @code{xtest}.

@item  %!testif HAVE_XXX
@itemx %!testif HAVE_XXX, HAVE_YYY, @dots{}
@itemx %!testif HAVE_XXX, HAVE_YYY @dots{}; RUNTIME_COND
@itemx %!testif @dots{} <MESSAGE>
Check block only if Octave was compiled with feature @w{@code{HAVE_XXX}}.
@w{@code{RUNTIME_COND}}@ is an optional expression to evaluate to check
whether some condition is met when the test is executed.  If
@w{@code{RUNTIME_COND}}@ is false, the test is skipped.  If @code{<MESSAGE>}
is present, the test block is interpreted as for @code{xtest}.

@item  %!xtest
@itemx %!xtest <MESSAGE>
Check block, report a test failure but do not abort testing.  If
@code{<MESSAGE>} is present, then the text of the message is displayed
if the test fails, like this:

@example
!!!!! known bug:  MESSAGE
@end example

@noindent
If the message is an integer, it is interpreted as a bug ID for the
Octave bug tracker and reported as

@example
!!!!! known bug: https://octave.org/testfailure/?BUG-ID
@end example

@noindent
in which BUG-ID is the integer bug number.  The intent is to allow
clearer documentation of known problems.

@noindent
If @code{MESSAGE} is an integer preceeded by an asterisk (e.g.,
@code{*12345}), it is interpreted as the id for a bug report that has
been closed.  That usually means that the issue probed in this test has
been resolved.  If such tests are failing, they are reported as
regressions by the @code{test} function:

@example
!!!!! regression: https://octave.org/testfailure/?BUG-ID
@end example


@item  %!error
@itemx %!error <MESSAGE>
@itemx %!warning
@itemx %!warning <MESSAGE>
Check for correct error or warning message.  If @code{<MESSAGE>} is
supplied it is interpreted as a regular expression pattern that is
expected to match the error or warning message.

@item %!demo
Demo only executes in interactive mode.

@item %!#
Comment.  Ignore everything within the block

@item %!shared x,y,z
Declare variables for use in multiple tests.

@item %!function
Define a function for use in multiple tests.

@item %!endfunction
Close a function definition.

@item %!assert (x, y, tol)

@item %!assert <MESSAGE> (x, y, tol)

@item %!fail (CODE, PATTERN)

@item %!fail <MESSAGE> (CODE, PATTERN)
Shorthand for @code{%!test assert (x, y, tol)} or
@code{%!test fail (CODE, PATTERN)}.  If @code{<MESSAGE>} is present, the
test block is interpreted as for @code{xtest}.

@end table

@anchor{test-message-anchor}

When coding tests the Octave convention is that lines that begin with a block
type do not have a semicolon at the end.  Any code that is within a block,
however, is normal Octave code and usually will have a trailing semicolon.
For example,

@example
@group
## bare block instantiation
%!assert (sin (0), 0)
@end group
@end example

@noindent
but

@example
@group
## test block with normal Octave code
%!test
%! assert (sin (0), 0);
@end group
@end example

You can also create test scripts for built-in functions and your own C++
functions.  To do so, put a file with the bare function name (no .m
extension) in a directory in the load path and it will be discovered by
the @code{test} function.  Alternatively, you can embed tests directly in your
C++ code:

@example
@group
/*
%!test disp ("this is a test")
*/
@end group
@end example

@noindent
or

@example
@group
#if 0
%!test disp ("this is a test")
#endif
@end group
@end example

@noindent
However, in this case the raw source code will need to be on the load
path and the user will have to remember to type
@code{test ("funcname.cc")}.

@DOCSTRING(assert)

@DOCSTRING(fail)

@node Demonstration Functions
@section Demonstration Functions

@DOCSTRING(demo)

@DOCSTRING(example)

@DOCSTRING(oruntests)

@DOCSTRING(rundemos)

@DOCSTRING(speed)