python module using boost python is empty?

I am trying to learn the boost python API to create my own python(3.6) module. I am able to successfully compile the following c++ code and get the resulting pythonTest.dll that I am generating.

#define BOOST_ALL_DYN_LINK
#include <boost/python.hpp>
#include <string>

const std::string hello_world(void)
{
    return std::string("hello world!\n");
}

BOOST_PYTHON_MODULE(pythonTest)
{
    namespace python = boost::python;

    python::def("hello_world", hello_world);
}

I then copy the pythonTest.dll to my module folder that looks like the following. (I rename the pythonTest.dll to pythonTest.pyd)

pythonTest\
    __init__.py
    pythonTest.pyd

When I execute python, it will import the module but it does not find my hello_world function:

Python 3.6.1 (v3.6.1:69c0db5, Mar 21 2017, 18:41:36) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import pythonTest
>>> pythonTest.hello_world()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
**AttributeError: module 'pythonTest' has no attribute 'hello_world'**

>>> help(pythonTest)
Help on package pythonTest:

NAME
    pythonTest

PACKAGE CONTENTS
    pythonTest

FILE
    <...>\pythontest\__init__.py

>>> dir(pythonTest)
['__builtins__', '__cached__', '__doc__', '__file__', '__loader__','__name__', '__package__', '__path__', '__spec__']
>>>

What am I missing? Thanks.

EDIT: This is the output from the visual studio build:

1>------ Rebuild All started: Project: pythonTest, Configuration: Release x64 ------
1>Build started 7/10/2017 2:49:53 PM.
1>InitializeBuildStatus:
1>  Creating "x64\Release\pythonTest.tlog\unsuccessfulbuild" because "AlwaysCreate" was specified.
1>ClCompile:
1>  pythonTest.cpp
1>G:\DataBackup\dev-vc13\3rdParty\boost_1_64_0\boost/python/detail/caller.hpp(55): warning C4244: 'return' : conversion from 'Py_ssize_t' to 'unsigned int', possible loss of data
1>Link:
1>     Creating library G:\DataBackup\dev-vc13\temp\pythonTest\x64\Release\pythonTest.lib and object G:\DataBackup\dev-vc13\temp\pythonTest\x64\Release\pythonTest.exp
1>  Generating code
1>  Finished generating code
1>  pythonTest.vcxproj -> G:\DataBackup\dev-vc13\temp\pythonTest\x64\Release\pythonTest.dll
1>PostBuildEvent:
1>          1 file(s) copied.
1>FinalizeBuildStatus:
1>  Deleting file "x64\Release\pythonTest.tlog\unsuccessfulbuild".
1>  Touching "x64\Release\pythonTest.tlog\pythonTest.lastbuildstate".
1>
1>Build succeeded.
1>
1>Time Elapsed 00:00:04.21
========== Rebuild All: 1 succeeded, 0 failed, 0 skipped ==========