googletest/samples/sample6_unittest.cc

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// This sample shows how to test common properties of multiple
// implementations of the same interface (aka interface tests).

// The interface and its implementations are in this header.
#include "prime_tables.h"

#include "gtest/gtest.h"
namespace {
// 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>()) {}

  ~PrimeTableTest() override { 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;

// 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_SUITE(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_SUITE(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_SUITE.  Sit back and be
// happy that you don't have to define them multiple times.

using testing::Types;

// 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_SUITE_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_SUITE_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_SUITE_P(OnTheFlyAndPreCalculated,    // Instance name
                               PrimeTableTest2,             // Test case name
                               PrimeTableImplementations);  // Type list

}  // namespace