testDouble: Update the test which will cause test fail
testDouble: Update the code to pass the test
Use MOCK_METHOD0 and  MOCK_CONST_METHOD1

EXPECT_CALL(httpStub, get(expectedURL));
It is to verify the input to the Mock object is correct.
testDouble: Add a new test which uses the mock to return a specified value
testDouble: In the test expects that the method initialize need be called.
testDouble: Pass the test but meet a GMOCK WARNING
testDouble: use NiceMock to suppress the warning.
testDouble: You can specify the sequence of the mock's methods.
Add a mock example which tests the out parameter
testDouble: use Factory method to inject the test double

There are constructor injection or setter injection. This one is
factory method injection.