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Add mock test for rcutils/strerror #265

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Merged
merged 21 commits into from
Jul 29, 2020
Merged

Add mock test for rcutils/strerror #265

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ae91f73
Add test using mimick vendored library
Blast545 Jul 3, 2020
18b53d1
Add path to mimick_vendor
Blast545 Jul 6, 2020
56782e7
Link test to mimick library
Blast545 Jul 7, 2020
2927385
Fix library usage issues
Blast545 Jul 7, 2020
7a7ec42
Fix mimick usage
Blast545 Jul 8, 2020
d3407d6
Remove commented code
Blast545 Jul 15, 2020
8338f9e
Add multi-platform support
Blast545 Jul 21, 2020
2135205
Reformat to separate different platform tests
Blast545 Jul 22, 2020
4e8b05d
Remove not needed constant
Blast545 Jul 22, 2020
dcf80fa
Reformat to use strncpy to copy buffer
Blast545 Jul 22, 2020
85d4d1a
Replace comments /* with //
Blast545 Jul 22, 2020
fe73174
Remove not needed constant for MacOs
Blast545 Jul 24, 2020
5b8ce8f
Remove extra parameter windows call
Blast545 Jul 27, 2020
1b3ad34
Cast function type
Blast545 Jul 27, 2020
fd8d93b
Add missing parentheses
Blast545 Jul 27, 2020
f00a0dc
Change reset macro to take strerror_mock
Blast545 Jul 27, 2020
0ffe78b
Use mallock return type to reset function
Blast545 Jul 27, 2020
200b5e0
Remove test_depend to mimick
Blast545 Jul 27, 2020
a870d60
Replace mock type
Blast545 Jul 27, 2020
ee41b34
Change function strncpy to strncpy_s
Blast545 Jul 27, 2020
a6cfb76
Add missing param
Blast545 Jul 27, 2020
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90 changes: 46 additions & 44 deletions test/test_strerror.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,7 @@ TEST(test_strerror, get_error) {
#endif
}

const char expected_error_msg[] = "Failed to get error";
/*
Define the blueprint of a mock identified by `strerror_r_proto`
strerror_r possible signatures:
Expand All @@ -67,78 +68,79 @@ TEST(test_strerror, get_error) {

#if defined(_WIN32)
mmk_mock_define(strerror_s_mock, errno_t, char *, rsize_t, errno_t);
#elif defined(_GNU_SOURCE) && (!defined(ANDROID) || __ANDROID_API__ >= 23)
mmk_mock_define(strerror_r_mock, char *, int, char *, size_t);
#else
mmk_mock_define(strerror_r_mock, int, int, char *, size_t);
#endif

const char expected_error_msg[] = "Failed to get error";
#if defined(_WIN32)
// Function to be called for (Case 3)
errno_t mocked_windows_strerror(char * buf, rsize_t bufsz, errno_t errnum)
{
(void) errnum;
unsigned char index_err = 0;

while (buf && bufsz--) {
buf[index_err] = expected_error_msg[index_err];
index_err++;
}
strncpy(buf, expected_error_msg, (size_t) bufsz);
return errnum;
}
#else
// Function to be called for (Case 1)

/* Mocking test example */
TEST(test_strerror, test_mock) {
/* Mock the strerror_s function in the current module using
the `strerror_s_mock` blueprint. */
mmk_mock(RCUTILS_STRINGIFY(strerror_s) "@lib:rcutils", strerror_s_mock);
/* Tell the mock to call mocked_windows_strerror instead*/
mmk_when(
strerror_s(mmk_any(errno_t), mmk_any(char *), mmk_any(rsize_t), mmk_any(errno_t)),
.then_call = (mmk_fn) mocked_windows_strerror);

// Set the error (not used by the mock)
errno = 2;
char error_string[1024];
rcutils_strerror(error_string, sizeof(error_string));
ASSERT_STREQ(error_string, "Failed to get error");
mmk_reset(strerror_s);
}

#elif defined(_GNU_SOURCE) && (!defined(ANDROID) || __ANDROID_API__ >= 23)
mmk_mock_define(strerror_r_mock, char *, int, char *, size_t);

char * mocked_gnu_strerror(int errnum, char * buf, size_t buflen)
{
(void) errnum;
const char error_msg[] = "Failed to get error";
unsigned char index_err = 0;
while (buf && buflen--) {
buf[index_err] = error_msg[index_err];
index_err++;
}
strncpy(buf, expected_error_msg, buflen);
return buf;
}
#endif

/* Mocking test example */
TEST(test_strerror, test_mock) {
/* Mock the strerror_r function in the current module using
the `strerror_r_mock` blueprint. */
#if defined(_WIN32)
mmk_mock(RCUTILS_STRINGIFY(strerror_s) "@lib:rcutils", strerror_s_mock);
#else
mmk_mock(RCUTILS_STRINGIFY(strerror_r) "@lib:rcutils", strerror_r_mock);
#endif
/* Tell the mock to return NULL and set errno to ENOMEM
whatever the given parameter is. */
#if defined(_WIN32)
mmk_when(
strerror_s(mmk_any(errno_t), mmk_any(char *), mmk_any(rsize_t), mmk_any(errno_t)),
.then_call = (mmk_fn) mocked_windows_strerror);
#elif defined(_GNU_SOURCE) && (!defined(ANDROID) || __ANDROID_API__ >= 23)
/* Tell the mock to call mocked_gnu_strerror instead */
mmk_when(
strerror_r(mmk_any(int), mmk_any(char *), mmk_any(size_t) ),
.then_call = (mmk_fn) mocked_gnu_strerror);

// Set the error (not used by the mock)
errno = 2;
char error_string[1024];
rcutils_strerror(error_string, sizeof(error_string));
ASSERT_STREQ(error_string, "Failed to get error");
mmk_reset(strerror_r);
}

#else
mmk_mock_define(strerror_r_mock, int, int, char *, size_t);
/* Mocking test example */
TEST(test_strerror, test_mock) {
/* Mock the strerror_r function in the current module using
the `strerror_r_mock` blueprint. */
mmk_mock(RCUTILS_STRINGIFY(strerror_r) "@lib:rcutils", strerror_r_mock);
/* Tell the mock to return NULL and set errno to EINVAL
whatever the given parameter is. */
mmk_when(
strerror_r(mmk_any(int), mmk_any(char *), mmk_any(size_t) ),
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@brawner brawner Jul 9, 2020

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This sets the global behavior of the mocked function? Are there reasonable scenarios where you might want the default behavior of the mocked function generally, but have the mocked version for one specific call? How might you accomplish that?

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@hidmic hidmic Jul 13, 2020 •
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Yeah, that's something I thought about, but unfortunately Mimick mocks do not explicitly support that feature. You could recreate behavior by building a table of mmk_when expressions, but it's impractical and brittle. I only know of gMock for a framework that can do that though.

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@hidmic hidmic Jul 21, 2020

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Uh, turns out it has the feature and @Blast545 found it 🎉

.then_return = mmk_val(int, EINVAL));
#endif

// Now normal usage of the function returning unexpected EINVAL
// error for the internal strerror_r
// This works only for POSIX

// Set the error "No such file or directory"
// Set the error "No such file or directory" (not used by the mock)
errno = 2;
char error_string[1024];
rcutils_strerror(error_string, sizeof(error_string));
ASSERT_STREQ(error_string, "Failed to get error");
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@brawner brawner Jul 9, 2020

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I'm sure this is a case-by-case matter, but what risks are there for maintainers adding calls to the mocked function that sits between the unit test and the targeted invocation? It seems like unit tests that call high-level functions, but mock low-level functions would be pretty brittle, and you would need to mock functions whose number of uses in the code under test is unlikely to change. rcutils_strerror is a good example where the number of uses of strerror_r are unlikely to change. Whereas mocking something like rcutils_strndup during complex code like rclcpp::init would result in behaviors that are difficult to assert.

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@hidmic hidmic Jul 13, 2020

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I don't see a fundamental risk, besides the maintenance burden that comes from white-box testing and the coupling between test and implementation it entails. It's important to bear in mind that mocking is not a tool for fault injection in a running system, but a way to unit test the interactions between the entity under test and its direct dependencies. In an rclcpp::init test, one would mock rcutils_strndup along with all other direct dependencies to ensure correct behavior.

#if defined(_WIN32)
mmk_reset(strerror_s);
#else
mmk_reset(strerror_r);
#endif
}

#endif