googletest/samples/sample6_unittest.cc

// Copyright 2008 Google Inc.
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// Author: wan@google.com (Zhanyong Wan)

// This sample shows how to test common properties of multiple
// implementations of the same interface (aka interface tests).  We
// put the code to be tested and the tests in the same file for
// simplicity.

#include <vector>
#include <gtest/gtest.h>

// Section 1. the interface and its implementations.

// The prime table interface.
class PrimeTable {
 public:
  virtual ~PrimeTable() {}

  // Returns true iff n is a prime number.
  virtual bool IsPrime(int n) const = 0;

  // Returns the smallest prime number greater than p; or returns -1
  // if the next prime is beyond the capacity of the table.
  virtual int GetNextPrime(int p) const = 0;
};

// Implementation #1 calculates the primes on-the-fly.
class OnTheFlyPrimeTable : public PrimeTable {
 public:
  virtual bool IsPrime(int n) const {
    if (n <= 1) return false;

    for (int i = 2; i*i <= n; i++) {
      // n is divisible by an integer other than 1 and itself.
      if ((n % i) == 0) return false;
    }

    return true;
  }

  virtual int GetNextPrime(int p) const {
    for (int n = p + 1; n > 0; n++) {
      if (IsPrime(n)) return n;
    }

    return -1;
  }
};

// Implementation #2 pre-calculates the primes and stores the result
// in a vector.
class PreCalculatedPrimeTable : public PrimeTable {
 public:
  // 'max' specifies the maximum number the prime table holds.
  explicit PreCalculatedPrimeTable(int max) : is_prime_(max + 1) {
    CalculatePrimesUpTo(max);
  }

  virtual bool IsPrime(int n) const {
    return 0 <= n && n < is_prime_.size() && is_prime_[n];
  }

  virtual int GetNextPrime(int p) const {
    for (int n = p + 1; n < is_prime_.size(); n++) {
      if (is_prime_[n]) return n;
    }

    return -1;
  }

 private:
  void CalculatePrimesUpTo(int max) {
    fill(is_prime_.begin(), is_prime_.end(), true);
    is_prime_[0] = is_prime_[1] = false;

    for (int i = 2; i <= max; i++) {
      if (!is_prime_[i]) continue;

      // Marks all multiples of i (except i itself) as non-prime.
      for (int j = 2*i; j <= max; j += i) {
        is_prime_[j] = false;
      }
    }
  }

  std::vector<bool> is_prime_;
};

// Sections 2. the tests.

// First, we define some factory functions for creating instances of
// the implementations.  You may be able to skip this step if all your
// implementations can be constructed the same way.

template <class T>
PrimeTable* CreatePrimeTable();

template <>
PrimeTable* CreatePrimeTable<OnTheFlyPrimeTable>() {
  return new OnTheFlyPrimeTable;
}

template <>
PrimeTable* CreatePrimeTable<PreCalculatedPrimeTable>() {
  return new PreCalculatedPrimeTable(10000);
}

// Then we define a test fixture class template.
template <class T>
class PrimeTableTest : public testing::Test {
 protected:
  // The ctor calls the factory function to create a prime table
  // implemented by T.
  PrimeTableTest() : table_(CreatePrimeTable<T>()) {}

  virtual ~PrimeTableTest() { delete table_; }

  // Note that we test an implementation via the base interface
  // instead of the actual implementation class.  This is important
  // for keeping the tests close to the real world scenario, where the
  // implementation is invoked via the base interface.  It avoids
  // got-yas where the implementation class has a method that shadows
  // a method with the same name (but slightly different argument
  // types) in the base interface, for example.
  PrimeTable* const table_;
};

using testing::Types;

#ifdef GTEST_HAS_TYPED_TEST

// Google Test offers two ways for reusing tests for different types.
// The first is called "typed tests".  You should use it if you
// already know *all* the types you are gonna exercise when you write
// the tests.

// To write a typed test case, first use
//
//   TYPED_TEST_CASE(TestCaseName, TypeList);
//
// to declare it and specify the type parameters.  As with TEST_F,
// TestCaseName must match the test fixture name.

// The list of types we want to test.
typedef Types<OnTheFlyPrimeTable, PreCalculatedPrimeTable> Implementations;

TYPED_TEST_CASE(PrimeTableTest, Implementations);

// Then use TYPED_TEST(TestCaseName, TestName) to define a typed test,
// similar to TEST_F.
TYPED_TEST(PrimeTableTest, ReturnsFalseForNonPrimes) {
  // Inside the test body, you can refer to the type parameter by
  // TypeParam, and refer to the fixture class by TestFixture.  We
  // don't need them in this example.

  // Since we are in the template world, C++ requires explicitly
  // writing 'this->' when referring to members of the fixture class.
  // This is something you have to learn to live with.
  EXPECT_FALSE(this->table_->IsPrime(-5));
  EXPECT_FALSE(this->table_->IsPrime(0));
  EXPECT_FALSE(this->table_->IsPrime(1));
  EXPECT_FALSE(this->table_->IsPrime(4));
  EXPECT_FALSE(this->table_->IsPrime(6));
  EXPECT_FALSE(this->table_->IsPrime(100));
}

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

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

// That's it!  Google Test will repeat each TYPED_TEST for each type
// in the type list specified in TYPED_TEST_CASE.  Sit back and be
// happy that you don't have to define them multiple times.

#endif  // GTEST_HAS_TYPED_TEST

#ifdef GTEST_HAS_TYPED_TEST_P

// Sometimes, however, you don't yet know all the types that you want
// to test when you write the tests.  For example, if you are the
// author of an interface and expect other people to implement it, you
// might want to write a set of tests to make sure each implementation
// conforms to some basic requirements, but you don't know what
// implementations will be written in the future.
//
// How can you write the tests without committing to the type
// parameters?  That's what "type-parameterized tests" can do for you.
// It is a bit more involved than typed tests, but in return you get a
// test pattern that can be reused in many contexts, which is a big
// win.  Here's how you do it:

// First, define a test fixture class template.  Here we just reuse
// the PrimeTableTest fixture defined earlier:

template <class T>
class PrimeTableTest2 : public PrimeTableTest<T> {
};

// Then, declare the test case.  The argument is the name of the test
// fixture, and also the name of the test case (as usual).  The _P
// suffix is for "parameterized" or "pattern".
TYPED_TEST_CASE_P(PrimeTableTest2);

// Next, use TYPED_TEST_P(TestCaseName, TestName) to define a test,
// similar to what you do with TEST_F.
TYPED_TEST_P(PrimeTableTest2, ReturnsFalseForNonPrimes) {
  EXPECT_FALSE(this->table_->IsPrime(-5));
  EXPECT_FALSE(this->table_->IsPrime(0));
  EXPECT_FALSE(this->table_->IsPrime(1));
  EXPECT_FALSE(this->table_->IsPrime(4));
  EXPECT_FALSE(this->table_->IsPrime(6));
  EXPECT_FALSE(this->table_->IsPrime(100));
}

TYPED_TEST_P(PrimeTableTest2, ReturnsTrueForPrimes) {
  EXPECT_TRUE(this->table_->IsPrime(2));
  EXPECT_TRUE(this->table_->IsPrime(3));
  EXPECT_TRUE(this->table_->IsPrime(5));
  EXPECT_TRUE(this->table_->IsPrime(7));
  EXPECT_TRUE(this->table_->IsPrime(11));
  EXPECT_TRUE(this->table_->IsPrime(131));
}

TYPED_TEST_P(PrimeTableTest2, CanGetNextPrime) {
  EXPECT_EQ(2, this->table_->GetNextPrime(0));
  EXPECT_EQ(3, this->table_->GetNextPrime(2));
  EXPECT_EQ(5, this->table_->GetNextPrime(3));
  EXPECT_EQ(7, this->table_->GetNextPrime(5));
  EXPECT_EQ(11, this->table_->GetNextPrime(7));
  EXPECT_EQ(131, this->table_->GetNextPrime(128));
}

// Type-parameterized tests involve one extra step: you have to
// enumerate the tests you defined:
REGISTER_TYPED_TEST_CASE_P(
    PrimeTableTest2,  // The first argument is the test case name.
    // The rest of the arguments are the test names.
    ReturnsFalseForNonPrimes, ReturnsTrueForPrimes, CanGetNextPrime);

// At this point the test pattern is done.  However, you don't have
// any real test yet as you haven't said which types you want to run
// the tests with.

// To turn the abstract test pattern into real tests, you instantiate
// it with a list of types.  Usually the test pattern will be defined
// in a .h file, and anyone can #include and instantiate it.  You can
// even instantiate it more than once in the same program.  To tell
// different instances apart, you give each of them a name, which will
// become part of the test case name and can be used in test filters.

// The list of types we want to test.  Note that it doesn't have to be
// defined at the time we write the TYPED_TEST_P()s.
typedef Types<OnTheFlyPrimeTable, PreCalculatedPrimeTable>
    PrimeTableImplementations;
INSTANTIATE_TYPED_TEST_CASE_P(OnTheFlyAndPreCalculated,    // Instance name
                              PrimeTableTest2,             // Test case name
                              PrimeTableImplementations);  // Type list

#endif  // GTEST_HAS_TYPED_TEST_P