使用模拟和死亡测试

Question

我发现 Google 测试的一个意想不到的行为，当涉及到死亡测试与对模拟对象的期望相结合时。

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 会针对意外调用 mock.foo():

发出警告

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.

我想这在某种程度上与使用 fork() 和线程进行死亡测试的警告有关，但我无法将所有部分匹配在一起。

Answer 1

这是一个known limitation的死亡测试。内部 assert_death 分叉，因此在子进程中调用的模拟未在父进程中注册。如果您希望抑制警告，请考虑使用 NiceMock.

Answer 2

如上正确回答，模拟调用未在子进程中注册。你必须在这个过程中写下你的 expect_calls 。以下应该有效：

TEST(BarTest, call_fooGetsCalledAndDies)
{
    InterfaceMock mock;

    ASSERT_DEATH({ [](){ EXPECT_CALL(mock, foo());
                         Bar().call(mock);} , "");
}

使用模拟和死亡测试

Using mocks and death tests

c++

unit-testing

googletest

googlemock