diff --git a/.pyup.yml b/.pyup.yml
new file mode 100644
index 0000000000..0c85ee8e03
--- /dev/null
+++ b/.pyup.yml
@@ -0,0 +1,24 @@
+# pyup.io config file
+# see https://pyup.io/docs/configuration/ for all available options
+
+schedule: every month
+
+requirements:
+  - requirements.txt:
+      pin: False
+      update: False
+  - requirements_test.txt:
+      pin: False
+      update: False
+  - requirements_rtfd.txt:
+      pin: False
+      update: False
+  - requirements_dev.txt:
+      pin: True
+      update: all
+  - requirements_dev_npy.txt:
+      pin: True
+      update: all
+  - requirements_dev_optional.txt:
+      pin: True
+      update: all
diff --git a/appveyor.yml b/appveyor.yml
index 987b51c1c4..67058550dc 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -12,49 +12,29 @@ environment:
 
   matrix:
 
-    - PYTHON: "C:\\Python27"
-      PYTHON_VERSION: "2.7"
-      NUMPY_VERSION: "1.15.2"
-
     - PYTHON: "C:\\Python27-x64"
       PYTHON_VERSION: "2.7"
-      NUMPY_VERSION: "1.15.2"
       DISTUTILS_USE_SDK: "1"
 
-    - PYTHON: "C:\\Python35"
-      PYTHON_VERSION: "3.5"
-      NUMPY_VERSION: "1.15.2"
-
     - PYTHON: "C:\\Python35-x64"
       PYTHON_VERSION: "3.5"
-      NUMPY_VERSION: "1.15.2"
-
-    - PYTHON: "C:\\Python36"
-      PYTHON_VERSION: "3.6"
-      NUMPY_VERSION: "1.15.2"
 
     - PYTHON: "C:\\Python36-x64"
       PYTHON_VERSION: "3.6"
-      NUMPY_VERSION: "1.15.2"
-
-    - PYTHON: "C:\\Python37"
-      PYTHON_VERSION: "3.7"
-      NUMPY_VERSION: "1.15.2"
 
     - PYTHON: "C:\\Python37-x64"
       PYTHON_VERSION: "3.7"
-      NUMPY_VERSION: "1.15.2"
 
 install:
   - "SET PATH=%PYTHON%;%PYTHON%\\Scripts;%PATH%"
+  - "%CMD_IN_ENV% python -m pip install -U pip setuptools wheel"
+  - "%CMD_IN_ENV% python -m pip install -rrequirements_test.txt"
+  - "%CMD_IN_ENV% python -m pip install -rrequirements_dev_npy.txt"
+  - "%CMD_IN_ENV% python -m pip install --no-binary=numcodecs -rrequirements_dev.txt"
+  - "%CMD_IN_ENV% python setup.py install"
+  - "%CMD_IN_ENV% python -m pip freeze"
 
 build: off
 
 test_script:
-  - "%CMD_IN_ENV% python -m pip install -U pip setuptools wheel"
-  - "%CMD_IN_ENV% python -m pip install numpy==%NUMPY_VERSION%"
-  - "%CMD_IN_ENV% python -m pip install cython==0.29"
-  - "%CMD_IN_ENV% python -m pip install -v --no-binary=numcodecs numcodecs==0.5.5"
-  - "%CMD_IN_ENV% python -m pip install -rrequirements_dev.txt"
-  - "%CMD_IN_ENV% python setup.py install"
   - "%CMD_IN_ENV% python -m pytest -v --pyargs zarr"
diff --git a/requirements.txt b/requirements.txt
index 8720210cf5..ab79134cb7 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 asciitree
-pytest
-numpy
 fasteners
 numcodecs
+numpy
+pytest
diff --git a/requirements_dev.txt b/requirements_dev.txt
index 23de426def..2ad18f372c 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -1,61 +1,3 @@
 asciitree==0.3.3
-asn1crypto==0.24.0
-atomicwrites==1.2.1
-attrs==18.2.0
-bleach==3.0.2
-boto3==1.9.26
-botocore==1.12.26
-certifi==2018.10.15
-cffi==1.11.5
-chardet==3.0.4
-cmarkgfm==0.4.2
-configparser==3.5.0
-coverage==4.5.1
-coveralls==1.5.1
-cryptography==2.3.1
-Cython==0.29
-docopt==0.6.2
-docutils==0.14
-enum34==1.1.6
 fasteners==0.14.1
-filelock==3.0.9
-flake8==3.5.0
-funcsigs==1.0.2
-future==0.16.0
-h5py==2.8.0
-idna==2.7
-ipaddress==1.0.22
-jmespath==0.9.3
-mccabe==0.6.1
-monotonic==1.5
-more-itertools==4.3.0
-msgpack-python==0.5.6
 numcodecs==0.5.5
-pathlib2==2.3.2
-pkginfo==1.4.2
-pluggy==0.8.0
-py==1.7.0
-pycodestyle==2.3.1
-pycparser==2.19
-pyflakes==1.6.0
-Pygments==2.2.0
-pyOpenSSL==18.0.0
-pytest==3.9.1
-pytest-cov==2.6.0
-python-dateutil==2.7.3
-readme-renderer==22.0
-requests==2.19.1
-requests-toolbelt==0.8.0
-setuptools-scm==3.1.0
-s3fs==0.1.6
-s3transfer==0.1.13
-scandir==1.9.0
-six==1.11.0
-toml==0.10.0
-tox==3.5.2
-tox-travis==0.11
-tqdm==4.27.0
-twine==1.12.1
-urllib3==1.23
-virtualenv==16.0.0
-webencodings==0.5.1
diff --git a/requirements_dev_npy.txt b/requirements_dev_npy.txt
new file mode 100644
index 0000000000..78b80223e2
--- /dev/null
+++ b/requirements_dev_npy.txt
@@ -0,0 +1,4 @@
+# Break this out into a separate file to allow testing against
+# different versions of numpy. This file should pin to the latest
+# numpy version.
+numpy==1.15.4
diff --git a/requirements_dev_optional.txt b/requirements_dev_optional.txt
index a4e7c2a6bd..1ea71451d9 100644
--- a/requirements_dev_optional.txt
+++ b/requirements_dev_optional.txt
@@ -1,2 +1,3 @@
+# These packages are currently not available on Windows.
 bsddb3==6.2.6
 lmdb==0.94
diff --git a/requirements_test.txt b/requirements_test.txt
new file mode 100644
index 0000000000..a668f130cc
--- /dev/null
+++ b/requirements_test.txt
@@ -0,0 +1,11 @@
+coverage
+coveralls
+cython
+flake8
+h5py
+msgpack-python
+pytest
+pytest-cov
+s3fs
+setuptools-scm
+tox
diff --git a/tox.ini b/tox.ini
index 7435b01f45..d443dec5df 100644
--- a/tox.ini
+++ b/tox.ini
@@ -30,11 +30,14 @@ commands =
     py37: python -m doctest -o NORMALIZE_WHITESPACE -o ELLIPSIS docs/tutorial.rst docs/spec/v2.rst
     # pep8 checks
     py37: flake8 --max-line-length=100 zarr
+    # print environment for debugging
+    pip freeze
 deps =
     py27: backports.lzma
     py36-npy113: numpy==1.13.3
     py36-npy114: numpy==1.14.6
-    py27,py35,py36-npy115,py37: numpy==1.15.2
+    py27,py35,py36-npy115,py37: -rrequirements_dev_npy.txt
+    -rrequirements_test.txt
     -rrequirements_dev.txt
     # linux only
     -rrequirements_dev_optional.txt