当 assert() 意外触发时，如何抑制 Google 测试中的终止？

Question

Here it's discussed how to catch failing assert, eg you setup your fixture so that assert() fails and you see nice output. But what I need is the opposite. I want to test that assert() succeeds. But in case it fails I want to have nice output. At that point it just terminates when it snags on assert().

#define LIMIT 5

struct Obj {
    int getIndex(int index) {
        assert(index < LIMIT);
        // do stuff;
    }
}

Obj obj;

TEST(Fails_whenOutOfRange) {
    ASSERT_DEATH(obj->getIndex(6), "");
}

TEST(Succeeds_whenInRange) {
    obj->getIndex(4);
}

Above is contrived example. I want second test not to terminate in case it fails, for example if I set LIMIT to 3. After all, ASSERT_DEATH suppresses somehow termination when assert() fails.

Answer 1

You should try using the command line option --gtest_break_on_failure

It is meant to run tests within a debugger, so you get a breakpoint upon test failure. If you don't use a debugger you'll just get a SEGFAULT and execution will stop.

Answer 2

The following is just my opinion, but it seems for me that you are either testing a wrong thing, or using a wrong tool.

Assert (C assert() ) is not for verifying input, it is for catching impossible situations. It will disappear from release code, for example, so you can't rely on it.

What you should test is your function specification rather than implementation . And you should decide, what is your specification for invalid input values:

• Undefined behavior, so assert is fine, but you can't test it with unit-test, because undefined behavior is, well , undefined.

• Defined behavior. Then you should be consistent regardless of NDEBUG presence. And throwing exception, in my opinion, is the right thing to do here, instead of calling std::abort , which is almost useless for user (can't be intercepted and processed properly).

Answer 3

If assert triggers (fails) you get "nice output" (or a crash or whatever assert does in your environment). If assert does not trigger then nothing happens and execution continues. What more do you need to know?

Answer 4

This (hack) adds a EXPECT_NODEATH macro to Google Test. It is the "opposite" of EXPECT_DEATH in that it will pass if the statement does not assert, abort, or otherwise fail.

The general idea was simple, but I did not take the time to make the error messages any nicer. I tried to leave Google Test as untouched as possible and just piggy-back on what is already there. You should be able to include this without any side effects to the rest of Google Test

For your case:

TEST(Succeeds_whenInRange) {
    EXPECT_NODEATH(obj->getIndex(4), "");
}

GTestNoDeath.h