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29 // Author: vladl@google.com (Vlad Losev)
30 
31 // This sample shows how to use Google Test listener API to implement
32 // a primitive leak checker.
33 
34 #include <stdio.h>
35 #include <stdlib.h>
36 
37 #include <gtest/gtest.h>
38 
39 using ::testing::EmptyTestEventListener;
40 using ::testing::InitGoogleTest;
41 using ::testing::Test;
42 using ::testing::TestCase;
43 using ::testing::TestEventListeners;
44 using ::testing::TestInfo;
45 using ::testing::TestPartResult;
46 using ::testing::UnitTest;
47 
48 namespace {
49 
50 // We will track memory used by this class.
51 class Water {
52  public:
53   // Normal Water declarations go here.
54 
55   // operator new and operator delete help us control water allocation.
operator new(size_t allocation_size)56   void* operator new(size_t allocation_size) {
57     allocated_++;
58     return malloc(allocation_size);
59   }
60 
operator delete(void * block,size_t)61   void operator delete(void* block, size_t /* allocation_size */) {
62     allocated_--;
63     free(block);
64   }
65 
allocated()66   static int allocated() { return allocated_; }
67 
68  private:
69   static int allocated_;
70 };
71 
72 int Water::allocated_ = 0;
73 
74 // This event listener monitors how many Water objects are created and
75 // destroyed by each test, and reports a failure if a test leaks some Water
76 // objects. It does this by comparing the number of live Water objects at
77 // the beginning of a test and at the end of a test.
78 class LeakChecker : public EmptyTestEventListener {
79  private:
80   // Called before a test starts.
OnTestStart(const TestInfo &)81   virtual void OnTestStart(const TestInfo& /* test_info */) {
82     initially_allocated_ = Water::allocated();
83   }
84 
85   // Called after a test ends.
OnTestEnd(const TestInfo &)86   virtual void OnTestEnd(const TestInfo& /* test_info */) {
87     int difference = Water::allocated() - initially_allocated_;
88 
89     // You can generate a failure in any event handler except
90     // OnTestPartResult. Just use an appropriate Google Test assertion to do
91     // it.
92     EXPECT_TRUE(difference <= 0)
93         << "Leaked " << difference << " unit(s) of Water!";
94   }
95 
96   int initially_allocated_;
97 };
98 
TEST(ListenersTest,DoesNotLeak)99 TEST(ListenersTest, DoesNotLeak) {
100   Water* water = new Water;
101   delete water;
102 }
103 
104 // This should fail when the --check_for_leaks command line flag is
105 // specified.
TEST(ListenersTest,LeaksWater)106 TEST(ListenersTest, LeaksWater) {
107   Water* water = new Water;
108   EXPECT_TRUE(water != NULL);
109 }
110 
111 }  // namespace
112 
main(int argc,char ** argv)113 int main(int argc, char **argv) {
114   InitGoogleTest(&argc, argv);
115 
116   bool check_for_leaks = false;
117   if (argc > 1 && strcmp(argv[1], "--check_for_leaks") == 0 )
118     check_for_leaks = true;
119   else
120     printf("%s\n", "Run this program with --check_for_leaks to enable "
121            "custom leak checking in the tests.");
122 
123   // If we are given the --check_for_leaks command line flag, installs the
124   // leak checker.
125   if (check_for_leaks) {
126     TestEventListeners& listeners = UnitTest::GetInstance()->listeners();
127 
128     // Adds the leak checker to the end of the test event listener list,
129     // after the default text output printer and the default XML report
130     // generator.
131     //
132     // The order is important - it ensures that failures generated in the
133     // leak checker's OnTestEnd() method are processed by the text and XML
134     // printers *before* their OnTestEnd() methods are called, such that
135     // they are attributed to the right test. Remember that a listener
136     // receives an OnXyzStart event *after* listeners preceding it in the
137     // list received that event, and receives an OnXyzEnd event *before*
138     // listeners preceding it.
139     //
140     // We don't need to worry about deleting the new listener later, as
141     // Google Test will do it.
142     listeners.Append(new LeakChecker);
143   }
144   return RUN_ALL_TESTS();
145 }
146