Google Testing Blog: TotT: Making a Perfect Matcher

TotT: Making a Perfect Matcher

Monday, October 05, 2009

by Zhanyong G. Mock Wan in Google Kirkland
Google C++ Mocking Framework matchers can make both your test code and your test output readableIt's easy to create a matcher that does exactly what you want, either by composing from existing matchers or by writing one from scratchcomposite matcherNot(m)mAnyOf(m1, ..., mn)ORAllOf(m1, ..., mn)ANDEXPECT_THAT(new_code, AnyOf(StartsWith(“// Tests”)),
              Not(ContainsRegex(“TODO.*intern”))));
Expected: (starts with “// Tests”) or
          (doesn't contain regular expression “TODO.*intern”)
Actual: “/* TODO: hire an intern. */ int main() {}”
The MATCHER macro lets you define a named matcherMATCHER(IsEven, “”) { return (arg % 2) == 0; }
EXPECT_THAT(paren_num, IsEven())notany codeautomatically generateExpected: is evenYou can also give multiple parameters to a matcher, or customize its description// P2 means the matcher has 2 parameters. Their names are low and high.

MATCHER_P2(InClosedRange, low, high, “is in range [%(low)s, %(high)s]”) {
  return low <= arg && arg <= high;
}
...
EXPECT_THAT(my_age, InClosedRange(adult_min, penalty_to_withdraw_401k)); Expected: is in range [18, 60]
  Actual: 2
Google C++ Mocking Framework uses compiler type inference to “write” the matcher parameter types for youToilet-Friendly Version

2 comments :

liam.listNovember 3, 2009 at 2:53:00 AM PST
I just do not get some of these matchers. Unit tests are meant to be consistent and repeatable, so I would be interested to find why you think there is a need for such matchers as the "in range" and "is even" ?
Surely the tests should be:
given a number x it is guaranteed to give number y. If you can not guarantee the output then it seems the code being tested has a smell, this being that it depends on global state.
ReplyDelete
Replies
Gil ZilberfeldNovember 11, 2009 at 5:36:00 AM PST
Hi Zhanyong,

My name is Gil Zilberfeld, and with my colleague Roy Osherove, we do a little cast called This week in testing.

This week we mention the new matcher feature, and talk about the Google mocking framework. I invite you to watch. If you like what you see, please talk about us, so more people can enjoy.

Thanks,

Gil Zilberfeld
Typemock
ReplyDelete
Replies

Add comment

The comments you read and contribute here belong only to the person who posted them. We reserve the right to remove off-topic comments.

Testing Blog

TotT: Making a Perfect Matcher

2 comments :

Labels

Archive

Feed

Subscribe by Email

Company-wide

Products

Developers