Trying to setup makefile for code + unit tests

I'm using Google test for the first time to write some unit tests. I made some very basic makefiles before, but I'm having some trouble modifying the Google test template (http://ift.tt/1XPqDEm).

My directory structure is:

.
├── bin/
├── Makefile
├── src/
│   ├── x.cpp
├── test/
│   └── tests.cc

I added my tests without a problem, but there are some issues:

• I want to put everything in the bin dir. I tried to do this by adding -o $(BIN_DIR)/$@, but then unittest couldn't find tests.o and gtest_main.a
• I also want to build code from my src dir.

This is what I have:

# A sample Makefile for building Google Test and using it in user
# tests.  Please tweak it to suit your environment and project.  You
# may want to move it to your project's root directory.
#
# SYNOPSIS:
#
#   make [all]  - makes everything.
#   make TARGET - makes the given target.
#   make clean  - removes all files generated by make.

# Please tweak the following variable definitions as needed by your
# project, except GTEST_HEADERS, which you can use in your own targets
# but shouldn't modify.

# Points to the root of Google Test, relative to where this file is.
# Remember to tweak this if you move this file.
GTEST_DIR = /home/aaron/googletest/googletest

# Where to find user code.
SRC_DIR = ./src
TEST_DIR = ./test
BIN_DIR = ./bin

# Flags passed to the preprocessor.
# Set Google Test's header directory as a system directory, such that
# the compiler doesn't generate warnings in Google Test headers.
CPPFLAGS += -isystem $(GTEST_DIR)/include

# Flags passed to the C++ compiler.
CXXFLAGS += -g -O0 -std=c++11 -pedantic -Wall -Wextra -pthread

# All tests produced by this Makefile.  Remember to add new tests you
# created to the list.
TESTS = unittest

# All Google Test headers.  Usually you shouldn't change this
# definition.
GTEST_HEADERS = $(GTEST_DIR)/include/gtest/*.h \
                $(GTEST_DIR)/include/gtest/internal/*.h

# House-keeping build targets.

all : $(TESTS)

clean :
    rm -rf $(BIN_DIR)/*

# Builds gtest.a and gtest_main.a.

# Usually you shouldn't tweak such internal variables, indicated by a
# trailing _.
GTEST_SRCS_ = $(GTEST_DIR)/src/*.cc $(GTEST_DIR)/src/*.h $(GTEST_HEADERS)

# For simplicity and to avoid depending on Google Test's
# implementation details, the dependencies specified below are
# conservative and not optimized.  This is fine as Google Test
# compiles fast and for ordinary users its source rarely changes.
gtest-all.o : $(GTEST_SRCS_)
    $(CXX) $(CPPFLAGS) -I$(GTEST_DIR) $(CXXFLAGS) -c \
            $(GTEST_DIR)/src/gtest-all.cc

gtest_main.o : $(GTEST_SRCS_)
    $(CXX) $(CPPFLAGS) -I$(GTEST_DIR) $(CXXFLAGS) -c \
            $(GTEST_DIR)/src/gtest_main.cc

gtest.a : gtest-all.o
    $(AR) $(ARFLAGS) $@ $^

gtest_main.a : gtest-all.o gtest_main.o
    $(AR) $(ARFLAGS) $@ $^

# Builds a sample test.  A test should link with either gtest.a or
# gtest_main.a, depending on whether it defines its own main()
# function.
tests.o : $(TEST_DIR)/tests.cc $(GTEST_HEADERS)
    $(CXX) $(CPPFLAGS) $(CXXFLAGS) -c $(TEST_DIR)/tests.cc

unittest : tests.o gtest_main.a 
    $(CXX) $(CPPFLAGS) $(CXXFLAGS) -lpthread $^ -o $@

Is there a larger template I use start with (not only for tests in this case) or what am I doing wrong?