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29 
30 
31 // This sample shows how to test code relying on some global flag variables.
32 // Combine() helps with generating all possible combinations of such flags,
33 // and each test is given one combination as a parameter.
34 
35 // Use class definitions to test from this header.
36 #include "prime_tables.h"
37 
38 #include "gtest/gtest.h"
39 namespace {
40 #if GTEST_HAS_COMBINE
41 
42 // Suppose we want to introduce a new, improved implementation of PrimeTable
43 // which combines speed of PrecalcPrimeTable and versatility of
44 // OnTheFlyPrimeTable (see prime_tables.h). Inside it instantiates both
45 // PrecalcPrimeTable and OnTheFlyPrimeTable and uses the one that is more
46 // appropriate under the circumstances. But in low memory conditions, it can be
47 // told to instantiate without PrecalcPrimeTable instance at all and use only
48 // OnTheFlyPrimeTable.
49 class HybridPrimeTable : public PrimeTable {
50  public:
51   HybridPrimeTable(bool force_on_the_fly, int max_precalculated)
52       : on_the_fly_impl_(new OnTheFlyPrimeTable),
53         precalc_impl_(force_on_the_fly ? NULL :
54                           new PreCalculatedPrimeTable(max_precalculated)),
55         max_precalculated_(max_precalculated) {}
56   virtual ~HybridPrimeTable() {
57     delete on_the_fly_impl_;
58     delete precalc_impl_;
59   }
60 
61   virtual bool IsPrime(int n) const {
62     if (precalc_impl_ != NULL && n < max_precalculated_)
63       return precalc_impl_->IsPrime(n);
64     else
65       return on_the_fly_impl_->IsPrime(n);
66   }
67 
68   virtual int GetNextPrime(int p) const {
69     int next_prime = -1;
70     if (precalc_impl_ != NULL && p < max_precalculated_)
71       next_prime = precalc_impl_->GetNextPrime(p);
72 
73     return next_prime != -1 ? next_prime : on_the_fly_impl_->GetNextPrime(p);
74   }
75 
76  private:
77   OnTheFlyPrimeTable* on_the_fly_impl_;
78   PreCalculatedPrimeTable* precalc_impl_;
79   int max_precalculated_;
80 };
81 
82 using ::testing::TestWithParam;
83 using ::testing::Bool;
84 using ::testing::Values;
85 using ::testing::Combine;
86 
87 // To test all code paths for HybridPrimeTable we must test it with numbers
88 // both within and outside PreCalculatedPrimeTable's capacity and also with
89 // PreCalculatedPrimeTable disabled. We do this by defining fixture which will
90 // accept different combinations of parameters for instantiating a
91 // HybridPrimeTable instance.
92 class PrimeTableTest : public TestWithParam< ::testing::tuple<bool, int> > {
93  protected:
94   virtual void SetUp() {
95     // This can be written as
96     //
97     // bool force_on_the_fly;
98     // int max_precalculated;
99     // tie(force_on_the_fly, max_precalculated) = GetParam();
100     //
101     // once the Google C++ Style Guide allows use of ::std::tr1::tie.
102     //
103     bool force_on_the_fly = ::testing::get<0>(GetParam());
104     int max_precalculated = ::testing::get<1>(GetParam());
105     table_ = new HybridPrimeTable(force_on_the_fly, max_precalculated);
106   }
107   virtual void TearDown() {
108     delete table_;
109     table_ = NULL;
110   }
111   HybridPrimeTable* table_;
112 };
113 
114 TEST_P(PrimeTableTest, ReturnsFalseForNonPrimes) {
115   // Inside the test body, you can refer to the test parameter by GetParam().
116   // In this case, the test parameter is a PrimeTable interface pointer which
117   // we can use directly.
118   // Please note that you can also save it in the fixture's SetUp() method
119   // or constructor and use saved copy in the tests.
120 
121   EXPECT_FALSE(table_->IsPrime(-5));
122   EXPECT_FALSE(table_->IsPrime(0));
123   EXPECT_FALSE(table_->IsPrime(1));
124   EXPECT_FALSE(table_->IsPrime(4));
125   EXPECT_FALSE(table_->IsPrime(6));
126   EXPECT_FALSE(table_->IsPrime(100));
127 }
128 
129 TEST_P(PrimeTableTest, ReturnsTrueForPrimes) {
130   EXPECT_TRUE(table_->IsPrime(2));
131   EXPECT_TRUE(table_->IsPrime(3));
132   EXPECT_TRUE(table_->IsPrime(5));
133   EXPECT_TRUE(table_->IsPrime(7));
134   EXPECT_TRUE(table_->IsPrime(11));
135   EXPECT_TRUE(table_->IsPrime(131));
136 }
137 
138 TEST_P(PrimeTableTest, CanGetNextPrime) {
139   EXPECT_EQ(2, table_->GetNextPrime(0));
140   EXPECT_EQ(3, table_->GetNextPrime(2));
141   EXPECT_EQ(5, table_->GetNextPrime(3));
142   EXPECT_EQ(7, table_->GetNextPrime(5));
143   EXPECT_EQ(11, table_->GetNextPrime(7));
144   EXPECT_EQ(131, table_->GetNextPrime(128));
145 }
146 
147 // In order to run value-parameterized tests, you need to instantiate them,
148 // or bind them to a list of values which will be used as test parameters.
149 // You can instantiate them in a different translation module, or even
150 // instantiate them several times.
151 //
152 // Here, we instantiate our tests with a list of parameters. We must combine
153 // all variations of the boolean flag suppressing PrecalcPrimeTable and some
154 // meaningful values for tests. We choose a small value (1), and a value that
155 // will put some of the tested numbers beyond the capability of the
156 // PrecalcPrimeTable instance and some inside it (10). Combine will produce all
157 // possible combinations.
158 INSTANTIATE_TEST_CASE_P(MeaningfulTestParameters,
159                         PrimeTableTest,
160                         Combine(Bool(), Values(1, 10)));
161 
162 #else
163 
164 // Google Test may not support Combine() with some compilers. If we
165 // use conditional compilation to compile out all code referring to
166 // the gtest_main library, MSVC linker will not link that library at
167 // all and consequently complain about missing entry point defined in
168 // that library (fatal error LNK1561: entry point must be
169 // defined). This dummy test keeps gtest_main linked in.
170 TEST(DummyTest, CombineIsNotSupportedOnThisPlatform) {}
171 
172 #endif  // GTEST_HAS_COMBINE
173 }  // namespace
174