GTEST - ASSERT_EQ and EXPECT_EQ compile error - c++

Question

I have been trying to use the assertion of ASSERT_EQ and EXPECT_EQ,
ASSERT_EQ(queue_->size(),6);
even using this
ASSERT_EQ(6,6);
However, I encountered this compiler error and everywhere I searched no one seems to be facing
this problem.
/tmp/cczZfMaq.o: In function testing::AssertionResult testing::internal::EqHelper<false>::Compare<char, char>(char const*, char const*, char const&, char const&)':
/usr/include/gtest/gtest.h:1485: undefined reference totesting::AssertionResult testing::internal::CmpHelperEQ(char const*, char const*, char const&, char const&)'
collect2: error: ld returned 1 exit status
make: * [priority_queue_test.out] Error 1
Full Test File :
//Include the class which you would like to test
#include "priority_queue.h"
//Include the google c++ test framework
#include
#include
#include
//use the namespace for the testing class
using namespace algorithms;
using namespace containers;
namespace{
//Test Fixture Class
//multple tests in a test case shared common objects and subroutines
class PriorityQueueTest : public ::testing::Test{
protected:
PriorityQueueTest(){
}
virtual ~PriorityQueueTest(){
}
virtual void SetUp(){
queue_ = new PriorityQueue(1000);
}
virtual void TearDown(){
}
PriorityQueue *queue_=NULL;
};
TEST_F(PriorityQueueTest,CheckAllMemberInitSuccessfully){
//ASSERT is a critcal assertion which will fail the test program
ASSERT_TRUE(queue_!=NULL) capacity()==1000) capacity();
}
TEST_F(PriorityQueueTest,CheckIfItemsAreEnqueueCorrectly){
//test cases
queue_->Enqueue(0,0);
queue_->Enqueue(1,1);
queue_->Enqueue(6,6);
queue_->Enqueue(5,5);
queue_->Enqueue(3,3);
queue_->Enqueue(2,2);
ASSERT_EQ('a','a');
}
}//namespace
int main(int argc, char *argv[]){
::testing::InitGoogleTest(&argc,argv);
return RUN_ALL_TESTS();
}