Recently I’ve played a bit with googletest in a couple of small projects: in murrayc-tuple-utils (and some later commits) and in prefixsuffix. It’s pretty straightforward and improved my test code and test result output (test-suite.log with autotools). Here are some notes.

Code Changes

I usually just use the standard autotools and CMake test features, sprinkling assert()s and “return EXIT_FAILURE;” in my C++ test code. However, googletest lets me replace a simple assert():

assert(foo.get_thing() == "hello");

with an EXPECT_EQ() call that will give me a clue when the test fails:
EXPECT_EQ("hello", foo.get_thing());

There are some other simple assertions.
googletest also wants me to declare test functions, previously simply declared like so,
void test_thing_something() {

now like so:
TEST("TestThing", "Something") {

which is all a bit macrotastic, unfortunately, but it works.
I chose to use the standard main() implementation, so I just removed my main() function that called these tests and compiled gtest_main.cc into the gtest library, as suggested in the googletest documentation.
Build Changes
googletest is meant to be built in your project, not built separately and just linked to as a library. For performance testing, I can see the benefit of building the test framework with exactly the same environment and options as the code being tested, but this does seem rather awkward. I guess it’s just what Google do in their monolithic builds so there’s nobody making an effort to support any other build system.
(Update: I wrote that in 2016, but now in 2019, I’ve noticed that added documentation about using pkg-config in August 2017 (now here) and removed that advice about building it yourself, in July 2018. I’m very pleased about that. However, your Linux distro probably doesn’t have a package for the library. The Debian googletest package and the Ubuntu googletest package (the same as the libgtest-dev package), for instance, “does not contain a library to link against, but rather the source code to build the google test and mock libraries”.
Anyway, it’s fairly easy to add googletest as a git submodule and build the library in your autotools or CMake project. For autotools, I did this with libtool in murrayc-tuple-utils and without libtool in prefixsuffix.
Unfortunately, I had to list the individual googletest source files in EXTRA_DIST to make this work with autotool’s “make distcheck”.
This is easier with CMake, because googletest has a CMakeList.txt file so you can use “add_subdirectory (googletest)”. Of course, CMake doesn’t have an equivalent for “make distcheck”.
Also unfortunately, I had to stop using the wonderful -Wsuggest-override warning with warnings as error, because googletest doesn’t use the override keyword. I think it hasn’t really caught up with C++11 yet, which seems odd as I guess Google is using at least C++11 in all its code.
Conclusion
The end result is not overwhelming so far, and it’s arguable if it’s worth having to deal with the git submodule awkwardness. But in theory, when the tests fail, I now won’t have to add so many printfs to find out what happened. This makes it a bit more like using JUnit with Java projects.
Also in theory, the test output would integrate nicely with a proper continuous integration system, such as Jenkins, or whatever Google use internally. But I’m not using any of those on these projects. Travis-CI is free with github projects, but it seems to be all about builds, with no support for test results.