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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 
     41 // Suppose we want to introduce a new, improved implementation of PrimeTable
     42 // which combines speed of PrecalcPrimeTable and versatility of
     43 // OnTheFlyPrimeTable (see prime_tables.h). Inside it instantiates both
     44 // PrecalcPrimeTable and OnTheFlyPrimeTable and uses the one that is more
     45 // appropriate under the circumstances. But in low memory conditions, it can be
     46 // told to instantiate without PrecalcPrimeTable instance at all and use only
     47 // OnTheFlyPrimeTable.
     48 class HybridPrimeTable : public PrimeTable {
     49  public:
     50   HybridPrimeTable(bool force_on_the_fly, int max_precalculated)
     51       : on_the_fly_impl_(new OnTheFlyPrimeTable),
     52         precalc_impl_(force_on_the_fly
     53                           ? nullptr
     54                           : new PreCalculatedPrimeTable(max_precalculated)),
     55         max_precalculated_(max_precalculated) {}
     56   ~HybridPrimeTable() override {
     57     delete on_the_fly_impl_;
     58     delete precalc_impl_;
     59   }
     60 
     61   bool IsPrime(int n) const override {
     62     if (precalc_impl_ != nullptr && n < max_precalculated_)
     63       return precalc_impl_->IsPrime(n);
     64     else
     65       return on_the_fly_impl_->IsPrime(n);
     66   }
     67 
     68   int GetNextPrime(int p) const override {
     69     int next_prime = -1;
     70     if (precalc_impl_ != nullptr && 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< ::std::tuple<bool, int> > {
     93  protected:
     94   void SetUp() override {
     95     bool force_on_the_fly;
     96     int max_precalculated;
     97     std::tie(force_on_the_fly, max_precalculated) = GetParam();
     98     table_ = new HybridPrimeTable(force_on_the_fly, max_precalculated);
     99   }
    100   void TearDown() override {
    101     delete table_;
    102     table_ = nullptr;
    103   }
    104   HybridPrimeTable* table_;
    105 };
    106 
    107 TEST_P(PrimeTableTest, ReturnsFalseForNonPrimes) {
    108   // Inside the test body, you can refer to the test parameter by GetParam().
    109   // In this case, the test parameter is a PrimeTable interface pointer which
    110   // we can use directly.
    111   // Please note that you can also save it in the fixture's SetUp() method
    112   // or constructor and use saved copy in the tests.
    113 
    114   EXPECT_FALSE(table_->IsPrime(-5));
    115   EXPECT_FALSE(table_->IsPrime(0));
    116   EXPECT_FALSE(table_->IsPrime(1));
    117   EXPECT_FALSE(table_->IsPrime(4));
    118   EXPECT_FALSE(table_->IsPrime(6));
    119   EXPECT_FALSE(table_->IsPrime(100));
    120 }
    121 
    122 TEST_P(PrimeTableTest, ReturnsTrueForPrimes) {
    123   EXPECT_TRUE(table_->IsPrime(2));
    124   EXPECT_TRUE(table_->IsPrime(3));
    125   EXPECT_TRUE(table_->IsPrime(5));
    126   EXPECT_TRUE(table_->IsPrime(7));
    127   EXPECT_TRUE(table_->IsPrime(11));
    128   EXPECT_TRUE(table_->IsPrime(131));
    129 }
    130 
    131 TEST_P(PrimeTableTest, CanGetNextPrime) {
    132   EXPECT_EQ(2, table_->GetNextPrime(0));
    133   EXPECT_EQ(3, table_->GetNextPrime(2));
    134   EXPECT_EQ(5, table_->GetNextPrime(3));
    135   EXPECT_EQ(7, table_->GetNextPrime(5));
    136   EXPECT_EQ(11, table_->GetNextPrime(7));
    137   EXPECT_EQ(131, table_->GetNextPrime(128));
    138 }
    139 
    140 // In order to run value-parameterized tests, you need to instantiate them,
    141 // or bind them to a list of values which will be used as test parameters.
    142 // You can instantiate them in a different translation module, or even
    143 // instantiate them several times.
    144 //
    145 // Here, we instantiate our tests with a list of parameters. We must combine
    146 // all variations of the boolean flag suppressing PrecalcPrimeTable and some
    147 // meaningful values for tests. We choose a small value (1), and a value that
    148 // will put some of the tested numbers beyond the capability of the
    149 // PrecalcPrimeTable instance and some inside it (10). Combine will produce all
    150 // possible combinations.
    151 INSTANTIATE_TEST_SUITE_P(MeaningfulTestParameters, PrimeTableTest,
    152                          Combine(Bool(), Values(1, 10)));
    153 
    154 }  // namespace
    155