gdbint.info: Testsuite

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Testsuite

The testsuite is an important component of the GDB package.  While it
is always worthwhile to encourage user testing, in practice this is
rarely sufficient; users typically use only a small subset of the
available commands, and it has proven all too common for a change to
cause a significant regression that went unnoticed for some time.
   The GDB testsuite uses the DejaGNU testing framework.  DejaGNU is
built using `Tcl' and `expect'.  The tests themselves are calls to
various `Tcl' procs; the framework runs all the procs and summarizes
the passes and fails.

Using the Testsuite

To run the testsuite, simply go to the GDB object directory (or to the
testsuite's objdir) and type `make check'.  This just sets up some
environment variables and invokes DejaGNU's `runtest' script.  While
the testsuite is running, you'll get mentions of which test file is in
use, and a mention of any unexpected passes or fails.  When the
testsuite is finished, you'll get a summary that looks like this:

=== gdb Summary ===

     # of expected passes            6016
     # of unexpected failures        58
     # of unexpected successes       5
     # of expected failures          183
     # of unresolved testcases       3
     # of untested testcases         5
   The ideal test run consists of expected passes only; however, reality
conspires to keep us from this ideal.  Unexpected failures indicate
real problems, whether in GDB or in the testsuite.  Expected failures
are still failures, but ones which have been decided are too hard to
deal with at the time; for instance, a test case might work everywhere
except on AIX, and there is no prospect of the AIX case being fixed in
the near future.  Expected failures should not be added lightly, since
you may be masking serious bugs in GDB.  Unexpected successes are
expected fails that are passing for some reason, while unresolved and
untested cases often indicate some minor catastrophe, such as the
compiler being unable to deal with a test program.
   When making any significant change to GDB, you should run the
testsuite before and after the change, to confirm that there are no
regressions.  Note that truly complete testing would require that you
run the testsuite with all supported configurations and a variety of
compilers; however this is more than really necessary.  In many cases
testing with a single configuration is sufficient.  Other useful
options are to test one big-endian (Sparc) and one little-endian (x86)
host, a cross config with a builtin simulator (powerpc-eabi, mips-elf),
or a 64-bit host (Alpha).
   If you add new functionality to GDB, please consider adding tests
for it as well; this way future GDB hackers can detect and fix their
changes that break the functionality you added.  Similarly, if you fix
a bug that was not previously reported as a test failure, please add a
test case for it.  Some cases are extremely difficult to test, such as
code that handles host OS failures or bugs in particular versions of
compilers, and it's OK not to try to write tests for all of those.

Testsuite Organization

The testsuite is entirely contained in `gdb/testsuite'.  While the
testsuite includes some makefiles and configury, these are very minimal,
and used for little besides cleaning up, since the tests themselves
handle the compilation of the programs that GDB will run.  The file
`testsuite/lib/gdb.exp' contains common utility procs useful for all
GDB tests, while the directory `testsuite/config' contains
configuration-specific files, typically used for special-purpose
definitions of procs like `gdb_load' and `gdb_start'.
   The tests themselves are to be found in `testsuite/gdb.*' and
subdirectories of those.  The names of the test files must always end
with `.exp'.  DejaGNU collects the test files by wildcarding in the
test directories, so both subdirectories and individual files get
chosen and run in alphabetical order.
   The following table lists the main types of subdirectories and what
they are for.  Since DejaGNU finds test files no matter where they are
located, and since each test file sets up its own compilation and
execution environment, this organization is simply for convenience and
intelligibility.
`gdb.base'
     This is the base testsuite.  The tests in it should apply to all
     configurations of GDB (but generic native-only tests may live
     here).  The test programs should be in the subset of C that is
     valid K&R, ANSI/ISO, and C++ (`#ifdef's are allowed if necessary,
     for instance for prototypes).
`gdb.LANG'
     Language-specific tests for any language LANG besides C.  Examples
     are `gdb.cp' and `gdb.java'.
`gdb.PLATFORM'
     Non-portable tests.  The tests are specific to a specific
     configuration (host or target), such as HP-UX or eCos.  Example is
     `gdb.hp', for HP-UX.
`gdb.COMPILER'
     Tests specific to a particular compiler.  As of this writing (June
     1999), there aren't currently any groups of tests in this category
     that couldn't just as sensibly be made platform-specific, but one
     could imagine a `gdb.gcc', for tests of GDB's handling of GCC
     extensions.
`gdb.SUBSYSTEM'
     Tests that exercise a specific GDB subsystem in more depth.  For
     instance, `gdb.disasm' exercises various disassemblers, while
     `gdb.stabs' tests pathways through the stabs symbol reader.

Writing Tests

In many areas, the GDB tests are already quite comprehensive; you
should be able to copy existing tests to handle new cases.
   You should try to use `gdb_test' whenever possible, since it
includes cases to handle all the unexpected errors that might happen.
However, it doesn't cost anything to add new test procedures; for
instance, `gdb.base/exprs.exp' defines a `test_expr' that calls
`gdb_test' multiple times.
   Only use `send_gdb' and `gdb_expect' when absolutely necessary, such
as when GDB has several valid responses to a command.
   The source language programs do _not_ need to be in a consistent
style.  Since GDB is used to debug programs written in many different
styles, it's worth having a mix of styles in the testsuite; for
instance, some GDB bugs involving the display of source lines would
never manifest themselves if the programs used GNU coding style
uniformly.