I have two immediate motivations for adding this:
1) It makes writing expectations in tests *dramatically* easier. A
quick example that is a taste of what is possible:
std::vector<int> v = ...;
EXPECT_THAT(v, UnorderedElementsAre(1, 2, 3));
This checks that v contains '1', '2', and '3' in some order. There
are a wealth of other helpful matchers like this. They tend to be
highly generic and STL-friendly so they will in almost all cases work
out of the box even on custom LLVM data structures.
I actually find the matcher syntax substantially easier to read even
for simple assertions:
EXPECT_THAT(a, Eq(b));
EXPECT_THAT(b, Ne(c));
Both of these make it clear what is being *tested* and what is being
*expected*. With `EXPECT_EQ` this is implicit (the LHS is expected,
the RHS is tested) and often confusing. With `EXPECT_NE` it is just
not clear. Even the failure error messages are superior with the
matcher based expectations.
2) When testing any kind of generic code, you are continually defining
dummy types with interfaces and then trying to check that the
interfaces are manipulated in a particular way. This is actually what
mocks are *good* for -- testing *interface interactions*. With
generic code, there is often no "fake" or other object that can be
used.
For a concrete example of where this is currently causing significant
pain, look at the pass manager unittests which are riddled with
counters incremented when methods are called. All of these could be
replaced with mocks. The result would be more effective at testing
the code by having tighter constraints. It would be substantially
more readable and maintainable when updating the code. And the error
messages on failure would have substantially more information as
mocks automatically record stack traces and other information *when
the API is misused* instead of trying to diagnose it after the fact.
I expect that #1 will be the overwhelming majority of the uses of gmock,
but I think that is sufficient to justify having it. I would actually
like to update the coding standards to encourage the use of matchers
rather than any other form of `EXPECT_...` macros as they are IMO
a strict superset in terms of functionality and readability.
I think that #2 is relatively rarely useful, but there *are* cases where
it is useful. Historically, I think misuse of actual mocking as
described in #2 has led to resistance towards this framework. I am
actually sympathetic to this -- mocking can easily be overused. However
I think this is not a significant concern in LLVM. First and foremost,
LLVM has very careful and rare exposure of abstract interfaces or
dependency injection, which are the most prone to abuse with mocks. So
there are few opportunities to abuse them. Second, a large fraction of
LLVM's unittests are testing *generic code* where mocks actually make
tremendous sense. And gmock is well suited to building interfaces that
exercise generic libraries. Finally, I still think we should be willing
to have testing utilities in tree even if they should be used rarely. We
can use code review to help guide the usage here.
For a longer and more complete discussion of this, see the llvm-dev
thread here:
http://lists.llvm.org/pipermail/llvm-dev/2017-January/108672.html
The general consensus seems that this is a reasonable direction to start
down, but that doesn't mean we should race ahead and use this
everywhere. I have one test that is blocked on this to land and that was
specifically used as an example. Before widespread adoption, I'm going
to work up some (brief) guidelines as some of these facilities should be
used sparingly and carefully.
Differential Revision: https://reviews.llvm.org/D28156
llvm-svn: 291606
Some GCC versions will accept any warning flag name after a '-Wno-',
which would cause us to try to disable warnings with names GCC didn't
understand. This will silently succeed unless there is some other output
from GCC in which case we get weird cc1plus warnings about the warning
name being bogus.
There is still the issue that gtest sets warning flags for building
gtest-all.cc using weird 'add_definitions' and the fact that there is
a GCC version which warns on the variadic macro usage in gtest under
-pedantic, but has no flag analogous to Clang's
-Wgnu-zero-variadic-macro-argumnets to suppress this warning. I haven't
been able to come up with any good solution here. The closest is to turn
off -pedantic for those versions of GCC, but that seems really nasty.
For now, those versinos of GCC aren't warning clean. If anyone is broken
by this, I'll work on CMake logic to detect and disable -pedantic in
these cases.
llvm-svn: 291299
This required re-working the streaming support and lit's support for
'--gtest_list_tests' but otherwise seems to be a clean upgrade.
Differential Revision: https://reviews.llvm.org/D28154
llvm-svn: 291029
Previously, gtest/gtest_main were not exported via cmake. The intention here was
to ensure that users whom are linking against the LLVM install tree would not
get the gtest/gtest_main targets. This prevents downstream projects that link
against the LLVM build tree (i.e. Swift) from getting this dependency
information in their cmake builds. Without such dependency information, linker
issues can result on linux due to LLVMSupport being put before gtest on the
linker command line.
This commit preserves behavior that we want for the install tree, while adding
support for the build tree by:
1. The special casing for gtest/gtest_main in the add_llvm_library code is
removed in favor of a flag called "BUILDTREE_ONLY". If this is set, then the
library is communicating that it is only meant to be exported into the build
tree and is not meant to be installed or exported via the install tree. This
part is just a tweak to remove the special case, the underlying code is the
same.
2. The cmake code that exports cmake targets for the build tree has special code
to import an additional targets file called
LLVMBuildTreeOnlyExports.cmake. Additionally the extra targets are added to the
LLVMConfig.cmake's LLVM_EXPORTED_TARGETS variable. In contrast, the
"installation" cmake file uses the normal LLVM_EXPORTS_TARGETS as before and
does not include the extra exports file. This is implemented by
defining/undefining variables when performing a configure of the build/install
tree LLVMConfig.cmake files.
llvm-svn: 281085
Patch by Jack Howarth.
When linking to libLLVM, don't also link to the component
libraries that constitute libLLVM.
Differential Revision: http://reviews.llvm.org/D16945
llvm-svn: 260641
ELF linkers by default allow shared libraries to contain undefined references
and it is up to the dynamic linker to look for them.
On COFF and MachO, that is not the case.
This creates a situation where a .so might build on an ELF system, but the build
of the corresponding .dylib or .dll will fail.
This patch changes the cmake build to use -Wl,-z,defs when linking and updates
the dependencies so that -DBUILD_SHARED_LIBS=ON build still works.
llvm-svn: 226611
externally to simplify our integration of GoogleTest into LLVM. Also,
build the single source file gtest-all.cc instead of the individual
source files as we don't expect these to change and thus gain nothing
from increased incrementality in compiles.
This makes our standard build of googletest exactly like upstream's
recommended build and the sanitizer's build. It also simplifies the
steps of importing a new version should we ever want one.
llvm-svn: 194801
available targets unless LLVM_INCLUDE_X is ON. LLVM_BUILD_X implies
LLVM_INCLUDE_X"
It breaks the configuration phase when cmake is invoked without
parameters, it is too complex for the purpose and introduces an
incovenience for the user (as both LLVM_BUILD_X and LLVM_INCLUDE_X
must set to OFF for not including X on the build)
llvm-svn: 114795
