Introduce a BeginEndDistanceIs matcher for containers such as std::forward_list

include/gmock/gmock-matchers.h

@@ -2267,6 +2267,67 @@ class SizeIsMatcher {
   GTEST_DISALLOW_ASSIGN_(SizeIsMatcher);
 };
 
+// Implements a matcher that checks the begin()..end() distance of an STL-style
+// container.
+template <typename DistanceMatcher>
+class BeginEndDistanceIsMatcher {
+ public:
+  explicit BeginEndDistanceIsMatcher(const DistanceMatcher& distance_matcher)
+      : distance_matcher_(distance_matcher) {}
+
+  template <typename Container>
+  operator Matcher<Container>() const {
+    return MakeMatcher(new Impl<Container>(distance_matcher_));
+  }
+
+  template <typename Container>
+  class Impl : public MatcherInterface<Container> {
+   public:
+    typedef internal::StlContainerView<
+        GTEST_REMOVE_REFERENCE_AND_CONST_(Container)> ContainerView;
+    typedef typename std::iterator_traits<
+        typename ContainerView::type::const_iterator>::difference_type
+        DistanceType;
+    explicit Impl(const DistanceMatcher& distance_matcher)
+        : distance_matcher_(MatcherCast<DistanceType>(distance_matcher)) {}
+
+    virtual void DescribeTo(::std::ostream* os) const {
+      *os << "distance between begin() and end() ";
+      distance_matcher_.DescribeTo(os);
+    }
+    virtual void DescribeNegationTo(::std::ostream* os) const {
+      *os << "distance between begin() and end() ";
+      distance_matcher_.DescribeNegationTo(os);
+    }
+
+    virtual bool MatchAndExplain(Container container,
+                                 MatchResultListener* listener) const {
+#if GTEST_LANG_CXX11
+      using std::begin;
+      using std::end;
+      DistanceType distance = std::distance(begin(container), end(container));
+#else
+      DistanceType distance = std::distance(container.begin(), container.end());
+#endif
+      StringMatchResultListener distance_listener;
+      const bool result =
+          distance_matcher_.MatchAndExplain(distance, &distance_listener);
+      *listener << "whose distance between begin() and end() " << distance
+                << (result ? " matches" : " doesn't match");
+      PrintIfNotEmpty(distance_listener.str(), listener->stream());
+      return result;
+    }
+
+   private:
+    const Matcher<DistanceType> distance_matcher_;
+    GTEST_DISALLOW_ASSIGN_(Impl);
+  };
+
+ private:
+  const DistanceMatcher distance_matcher_;
+  GTEST_DISALLOW_ASSIGN_(BeginEndDistanceIsMatcher);
+};
+
 // Implements an equality matcher for any STL-style container whose elements
 // support ==. This matcher is like Eq(), but its failure explanations provide
 // more detailed information that is useful when the container is used as a set.
@@ -3799,6 +3860,17 @@ SizeIs(const SizeMatcher& size_matcher) {
   return internal::SizeIsMatcher<SizeMatcher>(size_matcher);
 }
 
+// Returns a matcher that matches the distance between the container's begin()
+// iterator and its end() iterator, i.e. the size of the container. This matcher
+// can be used instead of SizeIs with containers such as std::forward_list which
+// do not implement size(). The container must provide const_iterator (with
+// valid iterator_traits), begin() and end().
+template <typename DistanceMatcher>
+inline internal::BeginEndDistanceIsMatcher<DistanceMatcher>
+BeginEndDistanceIs(const DistanceMatcher& distance_matcher) {
+  return internal::BeginEndDistanceIsMatcher<DistanceMatcher>(distance_matcher);
+}
+
 // Returns a matcher that matches an equal container.
 // This matcher behaves like Eq(), but in the event of mismatch lists the
 // values that are included in one container but not the other. (Duplicate

test/gmock-matchers_test.cc

@@ -54,6 +54,10 @@
 #include "gtest/gtest.h"
 #include "gtest/gtest-spi.h"
 
+#if GTEST_LANG_CXX11
+# include <forward_list>  // NOLINT
+#endif
+
 namespace testing {
 
 namespace internal {
@@ -4419,6 +4423,63 @@ TEST(StreamlikeTest, Iteration) {
   }
 }
 
+#if GTEST_LANG_CXX11
+TEST(BeginEndDistanceIsTest, WorksWithForwardList) {
+  std::forward_list<int> container;
+  EXPECT_THAT(container, BeginEndDistanceIs(0));
+  EXPECT_THAT(container, Not(BeginEndDistanceIs(1)));
+  container.push_front(0);
+  EXPECT_THAT(container, Not(BeginEndDistanceIs(0)));
+  EXPECT_THAT(container, BeginEndDistanceIs(1));
+  container.push_front(0);
+  EXPECT_THAT(container, Not(BeginEndDistanceIs(0)));
+  EXPECT_THAT(container, BeginEndDistanceIs(2));
+}
+#endif  // GTEST_LANG_CXX11
+
+TEST(BeginEndDistanceIsTest, WorksWithNonStdList) {
+  const int a[5] = { 1, 2, 3, 4, 5 };
+  Streamlike<int> s(a, a + 5);
+  EXPECT_THAT(s, BeginEndDistanceIs(5));
+}
+
+TEST(BeginEndDistanceIsTest, CanDescribeSelf) {
+  Matcher<vector<int> > m = BeginEndDistanceIs(2);
+  EXPECT_EQ("distance between begin() and end() is equal to 2", Describe(m));
+  EXPECT_EQ("distance between begin() and end() isn't equal to 2",
+            DescribeNegation(m));
+}
+
+TEST(BeginEndDistanceIsTest, ExplainsResult) {
+  Matcher<vector<int> > m1 = BeginEndDistanceIs(2);
+  Matcher<vector<int> > m2 = BeginEndDistanceIs(Lt(2));
+  Matcher<vector<int> > m3 = BeginEndDistanceIs(AnyOf(0, 3));
+  Matcher<vector<int> > m4 = BeginEndDistanceIs(GreaterThan(1));
+  vector<int> container;
+  EXPECT_EQ("whose distance between begin() and end() 0 doesn't match",
+            Explain(m1, container));
+  EXPECT_EQ("whose distance between begin() and end() 0 matches",
+            Explain(m2, container));
+  EXPECT_EQ("whose distance between begin() and end() 0 matches",
+            Explain(m3, container));
+  EXPECT_EQ(
+      "whose distance between begin() and end() 0 doesn't match, which is 1 "
+      "less than 1",
+      Explain(m4, container));
+  container.push_back(0);
+  container.push_back(0);
+  EXPECT_EQ("whose distance between begin() and end() 2 matches",
+            Explain(m1, container));
+  EXPECT_EQ("whose distance between begin() and end() 2 doesn't match",
+            Explain(m2, container));
+  EXPECT_EQ("whose distance between begin() and end() 2 doesn't match",
+            Explain(m3, container));
+  EXPECT_EQ(
+      "whose distance between begin() and end() 2 matches, which is 1 more "
+      "than 1",
+      Explain(m4, container));
+}
+
 TEST(WhenSortedTest, WorksForStreamlike) {
   // Streamlike 'container' provides only minimal iterator support.
   // Its iterators are tagged with input_iterator_tag.