1. Create a new unit test that uses mojo in a test binary that didn't already have any unit tests.
2. Spend a lot of time trying to figure out why you get a segfault like this:

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x00000000004ba407 in mojo::CreateMessagePipe(MojoCreateMessagePipeOptions const*, mojo::ScopedHandleBase<mojo::MessagePipeHandle>*, mojo::ScopedHandleBase<mojo::MessagePipeHandle>*) ()
#2  0x00000000004ba177 in mojo::MessagePipe::MessagePipe() ()
#3  0x00000000004ba00c in mojo::Binding<ui::mojom::UserActivityMonitor, mojo::RawPtrImplRefTraits<ui::mojom::UserActivityMonitor> >::Bind(mojo::InterfacePtr<ui::mojom::UserActivityMonitor>*, scoped_refptr<base::SingleThreadTaskRunner>) ()
#4  0x00000000004b93a3 in aura::UserActivityForwarderTest::SetUp() ()
#5  0x000000000057a828 in testing::Test::Run() ()
#6  0x000000000057b5b0 in testing::TestInfo::Run() ()
#7  0x000000000057ba47 in testing::TestCase::Run() ()
#8  0x0000000000582a87 in testing::internal::UnitTestImpl::RunAllTests() ()
#9  0x000000000058269a in testing::UnitTest::Run() ()
#10 0x000000000055e9f1 in base::TestSuite::Run() ()
#11 0x000000000055fd9e in base::(anonymous namespace)::LaunchUnitTestsInternal(base::Callback<int (), (base::internal::CopyMode)1, (base::internal::RepeatMode)1> const&, int, int, bool, base::Callback<void (), (base::internal::CopyMode)1, (base::internal::RepeatMode)1> con
st&) ()
#12 0x000000000055fc24 in base::LaunchUnitTests(int, char**, base::Callback<int (), (base::internal::CopyMode)1, (base::internal::RepeatMode)1> const&) ()
#13 0x00000000004dddaa in main ()

3. Finally realize that you need to make the test target depend on "//mojo/edk/system" and add a call to mojo::edk::Init() just before base::LaunchUnitTests() in the test binary's main() function.

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Is there some way we can make the cause of this failure (the mojo EDK being uninitialized, presumably) more obvious? I spent a lot of time digging through various CreateMessagePipe functions, thunks, etc. before I finally realized what was going on. The strategic addition of a debug-only call to a function named something like CheckEdkInitialized() would've been a huge help.