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// Author: vladl@google.com (Vlad Losev)

// This sample shows how to test code relying on some global flag variables.
// Combine() helps with generating all possible combinations of such flags,
// and each test is given one combination as a parameter.

// Use class definitions to test from this header.
#include "prime_tables.h"

#include "gtest/gtest.h"

#if GTEST_HAS_COMBINE

// Suppose we want to introduce a new, improved implementation of PrimeTable
// which combines speed of PrecalcPrimeTable and versatility of
// OnTheFlyPrimeTable (see prime_tables.h). Inside it instantiates both
// PrecalcPrimeTable and OnTheFlyPrimeTable and uses the one that is more
// appropriate under the circumstances. But in low memory conditions, it can be
// told to instantiate without PrecalcPrimeTable instance at all and use only
// OnTheFlyPrimeTable.
class HybridPrimeTable : public PrimeTable {
 public:
  HybridPrimeTable(bool force_on_the_fly, int max_precalculated)
      : on_the_fly_impl_(new OnTheFlyPrimeTable),
        precalc_impl_(force_on_the_fly ? NULL :
                          new PreCalculatedPrimeTable(max_precalculated)),
        max_precalculated_(max_precalculated) {}
  virtual ~HybridPrimeTable() {
    delete on_the_fly_impl_;
    delete precalc_impl_;
  }

  virtual bool IsPrime(int n) const {
    if (precalc_impl_ != NULL && n < max_precalculated_)
      return precalc_impl_->IsPrime(n);
    else
      return on_the_fly_impl_->IsPrime(n);
  }

  virtual int GetNextPrime(int p) const {
    int next_prime = -1;
    if (precalc_impl_ != NULL && p < max_precalculated_)
      next_prime = precalc_impl_->GetNextPrime(p);

    return next_prime != -1 ? next_prime : on_the_fly_impl_->GetNextPrime(p);
  }

 private:
  OnTheFlyPrimeTable* on_the_fly_impl_;
  PreCalculatedPrimeTable* precalc_impl_;
  int max_precalculated_;
};

using ::testing::TestWithParam;
using ::testing::Bool;
using ::testing::Values;
using ::testing::Combine;

// To test all code paths for HybridPrimeTable we must test it with numbers
// both within and outside PreCalculatedPrimeTable's capacity and also with
// PreCalculatedPrimeTable disabled. We do this by defining fixture which will
// accept different combinations of parameters for instantiating a
// HybridPrimeTable instance.
class PrimeTableTest : public TestWithParam< ::testing::tuple<bool, int> > {
 protected:
  virtual void SetUp() {
    // This can be written as
    //
    // bool force_on_the_fly;
    // int max_precalculated;
    // tie(force_on_the_fly, max_precalculated) = GetParam();
    //
    // once the Google C++ Style Guide allows use of ::std::tr1::tie.
    //
    bool force_on_the_fly = ::testing::get<0>(GetParam());
    int max_precalculated = ::testing::get<1>(GetParam());
    table_ = new HybridPrimeTable(force_on_the_fly, max_precalculated);
  }
  virtual void TearDown() {
    delete table_;
    table_ = NULL;
  }
  HybridPrimeTable* table_;
};

TEST_P(PrimeTableTest, ReturnsFalseForNonPrimes) {
  // Inside the test body, you can refer to the test parameter by GetParam().
  // In this case, the test parameter is a PrimeTable interface pointer which
  // we can use directly.
  // Please note that you can also save it in the fixture's SetUp() method
  // or constructor and use saved copy in the tests.

  EXPECT_FALSE(table_->IsPrime(-5));
  EXPECT_FALSE(table_->IsPrime(0));
  EXPECT_FALSE(table_->IsPrime(1));
  EXPECT_FALSE(table_->IsPrime(4));
  EXPECT_FALSE(table_->IsPrime(6));
  EXPECT_FALSE(table_->IsPrime(100));
}

TEST_P(PrimeTableTest, ReturnsTrueForPrimes) {
  EXPECT_TRUE(table_->IsPrime(2));
  EXPECT_TRUE(table_->IsPrime(3));
  EXPECT_TRUE(table_->IsPrime(5));
  EXPECT_TRUE(table_->IsPrime(7));
  EXPECT_TRUE(table_->IsPrime(11));
  EXPECT_TRUE(table_->IsPrime(131));
}

TEST_P(PrimeTableTest, CanGetNextPrime) {
  EXPECT_EQ(2, table_->GetNextPrime(0));
  EXPECT_EQ(3, table_->GetNextPrime(2));
  EXPECT_EQ(5, table_->GetNextPrime(3));
  EXPECT_EQ(7, table_->GetNextPrime(5));
  EXPECT_EQ(11, table_->GetNextPrime(7));
  EXPECT_EQ(131, table_->GetNextPrime(128));
}

// In order to run value-parameterized tests, you need to instantiate them,
// or bind them to a list of values which will be used as test parameters.
// You can instantiate them in a different translation module, or even
// instantiate them several times.
//
// Here, we instantiate our tests with a list of parameters. We must combine
// all variations of the boolean flag suppressing PrecalcPrimeTable and some
// meaningful values for tests. We choose a small value (1), and a value that
// will put some of the tested numbers beyond the capability of the
// PrecalcPrimeTable instance and some inside it (10). Combine will produce all
// possible combinations.
INSTANTIATE_TEST_CASE_P(MeaningfulTestParameters,
                        PrimeTableTest,
                        Combine(Bool(), Values(1, 10)));

#else

// Google Test may not support Combine() with some compilers. If we
// use conditional compilation to compile out all code referring to
// the gtest_main library, MSVC linker will not link that library at
// all and consequently complain about missing entry point defined in
// that library (fatal error LNK1561: entry point must be
// defined). This dummy test keeps gtest_main linked in.
TEST(DummyTest, CombineIsNotSupportedOnThisPlatform) {}

#endif  // GTEST_HAS_COMBINE
