Using mocks and death tests

Question

I have found an unexpected behavior of Google Test, when it comes to death tests combined with expectations on mock objects.

Check the following example:

#include <gmock/gmock.h>
#include <cassert>

class Interface
{
public:
    virtual void foo() = 0;
};

class InterfaceMock : public Interface
{
public:
    MOCK_METHOD0(foo, void());
};

class Bar
{
public:
    void call(Interface& interface)
    {
        interface.foo();
        assert(false);
    }
};


TEST(BarTest, call_fooGetsCalledAndDies)
{
    InterfaceMock mock;

    EXPECT_CALL(mock, foo());

    ASSERT_DEATH({ Bar().call(mock); }, "");
}

Test fails because expected call to mock.foo() fails to assert:

Running main() from gmock_main.cc
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from BarTest
[ RUN      ] BarTest.call_fooGetsCalledAndDies

[WARNING] /tmp/tmp.sHHkM/gmock-1.7.0/gtest/src/gtest-death-test.cc:825:: Death tests use fork(), which is unsafe particularly in a threaded context. For this test, Google Test couldn't detect the number of threads.
foo.cc:31: Failure
Actual function call count doesn't match EXPECT_CALL(mock, foo())...
         Expected: to be called once
           Actual: never called - unsatisfied and active
[  FAILED  ] BarTest.call_fooGetsCalledAndDies (1 ms)
[----------] 1 test from BarTest (1 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (2 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] BarTest.call_fooGetsCalledAndDies

 1 FAILED TEST

Interestingly, if the EXPECT_CALL(mock, foo()) line is commented, Google Mock raises a warning for an unexpected call to mock.foo():

Running main() from gmock_main.cc
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from BarTest
[ RUN      ] BarTest.call_fooGetsCalledAndDies

[WARNING] /tmp/tmp.sHHkM/gmock-1.7.0/gtest/src/gtest-death-test.cc:825:: Death tests use fork(), which is unsafe particularly in a threaded context. For this test, Google Test couldn't detect the number of threads.

GMOCK WARNING:
Uninteresting mock function call - returning directly.
    Function call: foo()
Stack trace:
[       OK ] BarTest.call_fooGetsCalledAndDies (1 ms)
[----------] 1 test from BarTest (1 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (1 ms total)
[  PASSED  ] 1 test.

I guess this is somehow related to the warning on death tests using fork() and threads, but I fail to match all pieces together.

Answer 1

This is a known limitation of death tests. Internally assert_death forks, so mocks called in the child are not registered in the parent process. If you wish to suppress the warnings, consider using NiceMock.