使用模拟和死亡测试

我发现Google测试有一个意想不到的行为，当涉及到死亡测试和对模拟对象的期望时。

检查以下示例：

#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); }, "");
}

测试失败，因为对mock.foo()的预期调用未能断言：

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

有趣的是，如果EXPECT_CALL(mock, foo())行被注释，Google Mock会发出警告，警告意外调用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.

我猜这与使用fork()和线程的死亡测试警告有关，但我无法将所有片段匹配在一起。

---

解决方案

这是known limitation死亡测试。在内部assert_death派生，因此在子进程中调用的模拟不会在父进程中注册。如果要取消显示警告，请考虑使用NiceMock。