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28 
29 // This sample shows how to use Google Test listener API to implement
30 // a primitive leak checker.
31 
32 #include <stdio.h>
33 #include <stdlib.h>
34 
35 #include "gtest/gtest.h"
36 using ::testing::EmptyTestEventListener;
37 using ::testing::InitGoogleTest;
38 using ::testing::Test;
39 using ::testing::TestEventListeners;
40 using ::testing::TestInfo;
41 using ::testing::UnitTest;
42 
43 namespace {
44 // We will track memory used by this class.
45 class Water {
46  public:
47   // Normal Water declarations go here.
48 
49   // operator new and operator delete help us control water allocation.
50   void* operator new(size_t allocation_size) {
51     allocated_++;
52     return malloc(allocation_size);
53   }
54 
55   void operator delete(void* block, size_t /* allocation_size */) {
56     allocated_--;
57     free(block);
58   }
59 
60   static int allocated() { return allocated_; }
61 
62  private:
63   static int allocated_;
64 };
65 
66 int Water::allocated_ = 0;
67 
68 // This event listener monitors how many Water objects are created and
69 // destroyed by each test, and reports a failure if a test leaks some Water
70 // objects. It does this by comparing the number of live Water objects at
71 // the beginning of a test and at the end of a test.
72 class LeakChecker : public EmptyTestEventListener {
73  private:
74   // Called before a test starts.
75   void OnTestStart(const TestInfo& /* test_info */) override {
76     initially_allocated_ = Water::allocated();
77   }
78 
79   // Called after a test ends.
80   void OnTestEnd(const TestInfo& /* test_info */) override {
81     int difference = Water::allocated() - initially_allocated_;
82 
83     // You can generate a failure in any event handler except
84     // OnTestPartResult. Just use an appropriate Google Test assertion to do
85     // it.
86     EXPECT_LE(difference, 0) << "Leaked " << difference << " unit(s) of Water!";
87   }
88 
89   int initially_allocated_;
90 };
91 
92 TEST(ListenersTest, DoesNotLeak) {
93   Water* water = new Water;
94   delete water;
95 }
96 
97 // This should fail when the --check_for_leaks command line flag is
98 // specified.
99 TEST(ListenersTest, LeaksWater) {
100   Water* water = new Water;
101   EXPECT_TRUE(water != nullptr);
102 }
103 }  // namespace
104 
105 int main(int argc, char** argv) {
106   InitGoogleTest(&argc, argv);
107 
108   bool check_for_leaks = false;
109   if (argc > 1 && strcmp(argv[1], "--check_for_leaks") == 0)
110     check_for_leaks = true;
111   else
112     printf("%s\n",
113            "Run this program with --check_for_leaks to enable "
114            "custom leak checking in the tests.");
115 
116   // If we are given the --check_for_leaks command line flag, installs the
117   // leak checker.
118   if (check_for_leaks) {
119     TestEventListeners& listeners = UnitTest::GetInstance()->listeners();
120 
121     // Adds the leak checker to the end of the test event listener list,
122     // after the default text output printer and the default XML report
123     // generator.
124     //
125     // The order is important - it ensures that failures generated in the
126     // leak checker's OnTestEnd() method are processed by the text and XML
127     // printers *before* their OnTestEnd() methods are called, such that
128     // they are attributed to the right test. Remember that a listener
129     // receives an OnXyzStart event *after* listeners preceding it in the
130     // list received that event, and receives an OnXyzEnd event *before*
131     // listeners preceding it.
132     //
133     // We don't need to worry about deleting the new listener later, as
134     // Google Test will do it.
135     listeners.Append(new LeakChecker);
136   }
137   return RUN_ALL_TESTS();
138 }
139