example.cpp

#include "gtest/gtest.h"

// Returns n! (the factorial of n).  For negative n, n! is defined to be 1.
int Factorial(int n)
{
  int result = 1;
  for (int i = 1; i <= n; i++)
  {
    result *= i;
  }

  return result;
}

// Returns true iff n is a prime number.
bool IsPrime(int n)
{
  // Trivial case 1: small numbers
  if (n <= 1)
    return false;

  // Trivial case 2: even numbers
  if (n % 2 == 0)
    return n == 2;

  // Now, we have that n is odd and n >= 3.

  // Try to divide n by every odd number i, starting from 3
  for (int i = 3;; i += 2)
  {
    // We only have to try i up to the square root of n
    if (i > n / i)
      break;

    // Now, we have i <= n/i < n.
    // If n is divisible by i, n is not prime.
    if (n % i == 0)
      return false;
  }

  // n has no integer factor in the range (1, n), and thus is prime.
  return true;
}
namespace
{
TEST(Factorial, Negative)
{
  EXPECT_EQ(1, Factorial(-1));
}
TEST(IsPrime, 2){
EXPECT_EQ(true, IsPrime(2));
}
}