How to initialize constant string for multiple tests in google test? - tdd

Question

I'm using google test and I have a cpp-file containing several tests. I would like to initialize a string with the current date and time when starting the first test. I would like to use this string in all other tests, too. How can I do this.
I've tried the following (m_string being a protected member of CnFirstTest), but it didn't work (since the constructor and SetUp will be called before each test):
CnFirstTest::CnFirstTest(void) {
m_string = currentDateTime();
}
void CnFirstTest::SetUp() {
}
TEST_F(CnFirstTest, Test1) {
// use m_string
}
TEST_F(CnFirstTest, Test2) {
// use m_string, too
}

Answer 1

You can use a gtest testing::Environment to achieve this:
#include <chrono>
#include <iostream>
#include "gtest/gtest.h"
std::string currentDateTime() {
return std::to_string(std::chrono::steady_clock::now().time_since_epoch().count());
}
class TestEnvironment : public ::testing::Environment {
public:
// Assume there's only going to be a single instance of this class, so we can just
// hold the timestamp as a const static local variable and expose it through a
// static member function
static std::string getStartTime() {
static const std::string timestamp = currentDateTime();
return timestamp;
}
// Initialise the timestamp.
virtual void SetUp() { getStartTime(); }
};
class CnFirstTest : public ::testing::Test {
protected:
virtual void SetUp() { m_string = currentDateTime(); }
std::string m_string;
};
TEST_F(CnFirstTest, Test1) {
std::cout << TestEnvironment::getStartTime() << std::endl;
std::cout << m_string << std::endl;
}
TEST_F(CnFirstTest, Test2) {
std::cout << TestEnvironment::getStartTime() << std::endl;
std::cout << m_string << std::endl;
}
int main(int argc, char* argv[]) {
::testing::InitGoogleTest(&argc, argv);
// gtest takes ownership of the TestEnvironment ptr - we don't delete it.
::testing::AddGlobalTestEnvironment(new TestEnvironment);
return RUN_ALL_TESTS();
}