diff --git a/.github/workflows/pythonpackage.yml b/.github/workflows/pythonpackage.yml
index d425478b..b7fcfabe 100644
--- a/.github/workflows/pythonpackage.yml
+++ b/.github/workflows/pythonpackage.yml
@@ -20,14 +20,12 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install poetry
+          pip install -r requirements-dev.txt
           poetry install
       - name: Typecheck with mypy
         run: |
-          pip install mypy
           make typecheck
       - name: Test with pytest
         run: |
-          pip install pytest
           pip install .
           python -m pytest tests/ -v
diff --git a/poetry.lock b/poetry.lock
index 983cd948..00a62779 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,62 +1,3 @@
-[[package]]
-category = "dev"
-description = "A small Python module for determining appropriate platform-specific dirs, e.g. a \"user data dir\"."
-name = "appdirs"
-optional = false
-python-versions = "*"
-version = "1.4.4"
-
-[[package]]
-category = "dev"
-description = "Atomic file writes."
-marker = "sys_platform == \"win32\""
-name = "atomicwrites"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
-version = "1.4.0"
-
-[[package]]
-category = "dev"
-description = "Classes Without Boilerplate"
-name = "attrs"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
-version = "19.3.0"
-
-[package.extras]
-azure-pipelines = ["coverage", "hypothesis", "pympler", "pytest (>=4.3.0)", "six", "zope.interface", "pytest-azurepipelines"]
-dev = ["coverage", "hypothesis", "pympler", "pytest (>=4.3.0)", "six", "zope.interface", "sphinx", "pre-commit"]
-docs = ["sphinx", "zope.interface"]
-tests = ["coverage", "hypothesis", "pympler", "pytest (>=4.3.0)", "six", "zope.interface"]
-
-[[package]]
-category = "dev"
-description = "The uncompromising code formatter."
-name = "black"
-optional = false
-python-versions = ">=3.6"
-version = "19.10b0"
-
-[package.dependencies]
-appdirs = "*"
-attrs = ">=18.1.0"
-click = ">=6.5"
-pathspec = ">=0.6,<1"
-regex = "*"
-toml = ">=0.9.4"
-typed-ast = ">=1.4.0"
-
-[package.extras]
-d = ["aiohttp (>=3.3.2)", "aiohttp-cors"]
-
-[[package]]
-category = "dev"
-description = "Composable command line interface toolkit"
-name = "click"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
-version = "7.1.2"
-
 [[package]]
 category = "main"
 description = "Cross-platform colored terminal text."
@@ -85,90 +26,6 @@ optional = false
 python-versions = ">=3.6, <3.7"
 version = "0.7"
 
-[[package]]
-category = "dev"
-description = "Read metadata from Python packages"
-marker = "python_version < \"3.8\""
-name = "importlib-metadata"
-optional = false
-python-versions = "!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*,>=2.7"
-version = "1.6.1"
-
-[package.dependencies]
-zipp = ">=0.5"
-
-[package.extras]
-docs = ["sphinx", "rst.linker"]
-testing = ["packaging", "pep517", "importlib-resources (>=1.3)"]
-
-[[package]]
-category = "dev"
-description = "More routines for operating on iterables, beyond itertools"
-name = "more-itertools"
-optional = false
-python-versions = ">=3.5"
-version = "8.4.0"
-
-[[package]]
-category = "dev"
-description = "Optional static typing for Python"
-name = "mypy"
-optional = false
-python-versions = ">=3.5"
-version = "0.781"
-
-[package.dependencies]
-mypy-extensions = ">=0.4.3,<0.5.0"
-typed-ast = ">=1.4.0,<1.5.0"
-typing-extensions = ">=3.7.4"
-
-[package.extras]
-dmypy = ["psutil (>=4.0)"]
-
-[[package]]
-category = "dev"
-description = "Experimental type system extensions for programs checked with the mypy typechecker."
-name = "mypy-extensions"
-optional = false
-python-versions = "*"
-version = "0.4.3"
-
-[[package]]
-category = "dev"
-description = "Core utilities for Python packages"
-name = "packaging"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
-version = "20.4"
-
-[package.dependencies]
-pyparsing = ">=2.0.2"
-six = "*"
-
-[[package]]
-category = "dev"
-description = "Utility library for gitignore style pattern matching of file paths."
-name = "pathspec"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
-version = "0.8.0"
-
-[[package]]
-category = "dev"
-description = "plugin and hook calling mechanisms for python"
-name = "pluggy"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
-version = "0.13.1"
-
-[package.dependencies]
-[package.dependencies.importlib-metadata]
-python = "<3.8"
-version = ">=0.12"
-
-[package.extras]
-dev = ["pre-commit", "tox"]
-
 [[package]]
 category = "main"
 description = "A drop-in replacement for pprint that's actually pretty"
@@ -177,14 +34,6 @@ optional = false
 python-versions = "*"
 version = "0.4.0"
 
-[[package]]
-category = "dev"
-description = "library with cross-python path, ini-parsing, io, code, log facilities"
-name = "py"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
-version = "1.8.2"
-
 [[package]]
 category = "main"
 description = "Pygments is a syntax highlighting package written in Python."
@@ -193,126 +42,19 @@ optional = false
 python-versions = ">=3.5"
 version = "2.6.1"
 
-[[package]]
-category = "dev"
-description = "Python parsing module"
-name = "pyparsing"
-optional = false
-python-versions = ">=2.6, !=3.0.*, !=3.1.*, !=3.2.*"
-version = "2.4.7"
-
-[[package]]
-category = "dev"
-description = "pytest: simple powerful testing with Python"
-name = "pytest"
-optional = false
-python-versions = ">=3.5"
-version = "5.4.3"
-
-[package.dependencies]
-atomicwrites = ">=1.0"
-attrs = ">=17.4.0"
-colorama = "*"
-more-itertools = ">=4.0.0"
-packaging = "*"
-pluggy = ">=0.12,<1.0"
-py = ">=1.5.0"
-wcwidth = "*"
-
-[package.dependencies.importlib-metadata]
-python = "<3.8"
-version = ">=0.12"
-
-[package.extras]
-checkqa-mypy = ["mypy (v0.761)"]
-testing = ["argcomplete", "hypothesis (>=3.56)", "mock", "nose", "requests", "xmlschema"]
-
-[[package]]
-category = "dev"
-description = "Alternative regular expression module, to replace re."
-name = "regex"
-optional = false
-python-versions = "*"
-version = "2020.6.8"
-
-[[package]]
-category = "dev"
-description = "Python 2 and 3 compatibility utilities"
-name = "six"
-optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*"
-version = "1.15.0"
-
-[[package]]
-category = "dev"
-description = "Python Library for Tom's Obvious, Minimal Language"
-name = "toml"
-optional = false
-python-versions = "*"
-version = "0.10.1"
-
-[[package]]
-category = "dev"
-description = "a fork of Python 2 and 3 ast modules with type comment support"
-name = "typed-ast"
-optional = false
-python-versions = "*"
-version = "1.4.1"
-
 [[package]]
 category = "main"
 description = "Backported and Experimental Type Hints for Python 3.5+"
 name = "typing-extensions"
 optional = false
 python-versions = "*"
-version = "3.7.4.1"
-
-[[package]]
-category = "dev"
-description = "Measures the displayed width of unicode strings in a terminal"
-name = "wcwidth"
-optional = false
-python-versions = "*"
-version = "0.2.4"
-
-[[package]]
-category = "dev"
-description = "Backport of pathlib-compatible object wrapper for zip files"
-marker = "python_version < \"3.8\""
-name = "zipp"
-optional = false
-python-versions = ">=3.6"
-version = "3.1.0"
-
-[package.extras]
-docs = ["sphinx", "jaraco.packaging (>=3.2)", "rst.linker (>=1.9)"]
-testing = ["jaraco.itertools", "func-timeout"]
+version = "3.7.4.2"
 
 [metadata]
-content-hash = "ed1ddb751dca29f2b71612a12dee91264fd4797ac911418e868743e9763a281e"
+content-hash = "fd939f72e4c9832fda8ddbe2a399155a6bdc33353d9dceb029944328a1968755"
 python-versions = "^3.6"
 
 [metadata.files]
-appdirs = [
-    {file = "appdirs-1.4.4-py2.py3-none-any.whl", hash = "sha256:a841dacd6b99318a741b166adb07e19ee71a274450e68237b4650ca1055ab128"},
-    {file = "appdirs-1.4.4.tar.gz", hash = "sha256:7d5d0167b2b1ba821647616af46a749d1c653740dd0d2415100fe26e27afdf41"},
-]
-atomicwrites = [
-    {file = "atomicwrites-1.4.0-py2.py3-none-any.whl", hash = "sha256:6d1784dea7c0c8d4a5172b6c620f40b6e4cbfdf96d783691f2e1302a7b88e197"},
-    {file = "atomicwrites-1.4.0.tar.gz", hash = "sha256:ae70396ad1a434f9c7046fd2dd196fc04b12f9e91ffb859164193be8b6168a7a"},
-]
-attrs = [
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-    {file = "attrs-19.3.0.tar.gz", hash = "sha256:f7b7ce16570fe9965acd6d30101a28f62fb4a7f9e926b3bbc9b61f8b04247e72"},
-]
-black = [
-    {file = "black-19.10b0-py36-none-any.whl", hash = "sha256:1b30e59be925fafc1ee4565e5e08abef6b03fe455102883820fe5ee2e4734e0b"},
-    {file = "black-19.10b0.tar.gz", hash = "sha256:c2edb73a08e9e0e6f65a0e6af18b059b8b1cdd5bef997d7a0b181df93dc81539"},
-]
-click = [
-    {file = "click-7.1.2-py2.py3-none-any.whl", hash = "sha256:dacca89f4bfadd5de3d7489b7c8a566eee0d3676333fbb50030263894c38c0dc"},
-    {file = "click-7.1.2.tar.gz", hash = "sha256:d2b5255c7c6349bc1bd1e59e08cd12acbbd63ce649f2588755783aa94dfb6b1a"},
-]
 colorama = [
     {file = "colorama-0.4.3-py2.py3-none-any.whl", hash = "sha256:7d73d2a99753107a36ac6b455ee49046802e59d9d076ef8e47b61499fa29afff"},
     {file = "colorama-0.4.3.tar.gz", hash = "sha256:e96da0d330793e2cb9485e9ddfd918d456036c7149416295932478192f4436a1"},
@@ -325,130 +67,16 @@ dataclasses = [
     {file = "dataclasses-0.7-py3-none-any.whl", hash = "sha256:3459118f7ede7c8bea0fe795bff7c6c2ce287d01dd226202f7c9ebc0610a7836"},
     {file = "dataclasses-0.7.tar.gz", hash = "sha256:494a6dcae3b8bcf80848eea2ef64c0cc5cd307ffc263e17cdf42f3e5420808e6"},
 ]
-importlib-metadata = [
-    {file = "importlib_metadata-1.6.1-py2.py3-none-any.whl", hash = "sha256:15ec6c0fd909e893e3a08b3a7c76ecb149122fb14b7efe1199ddd4c7c57ea958"},
-    {file = "importlib_metadata-1.6.1.tar.gz", hash = "sha256:0505dd08068cfec00f53a74a0ad927676d7757da81b7436a6eefe4c7cf75c545"},
-]
-more-itertools = [
-    {file = "more-itertools-8.4.0.tar.gz", hash = "sha256:68c70cc7167bdf5c7c9d8f6954a7837089c6a36bf565383919bb595efb8a17e5"},
-    {file = "more_itertools-8.4.0-py3-none-any.whl", hash = "sha256:b78134b2063dd214000685165d81c154522c3ee0a1c0d4d113c80361c234c5a2"},
-]
-mypy = [
-    {file = "mypy-0.781-cp35-cp35m-macosx_10_6_x86_64.whl", hash = "sha256:43335f3ff3288eb877de6d186ec08e10ea61093405189678756e14c7ccee4a9b"},
-    {file = "mypy-0.781-cp35-cp35m-manylinux1_x86_64.whl", hash = "sha256:d7c9255ba6626e1745bd68e1b85e3d7888844eaf38252fefb8157194e55fd3e9"},
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diff --git a/pyproject.toml b/pyproject.toml
index e7e3e223..dd3cb57a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -32,9 +32,6 @@ colorama = "^0.4.0"
 
 
 [tool.poetry.dev-dependencies]
-pytest = "^5.4.3"
-mypy = "^0.781"
-black = "^19.10b0"
 
 [build-system]
 requires = ["poetry>=0.12"]
diff --git a/requirements-dev.txt b/requirements-dev.txt
new file mode 100644
index 00000000..bd7b9603
--- /dev/null
+++ b/requirements-dev.txt
@@ -0,0 +1,4 @@
+black==19.10b0
+mypy==0.781
+poetry==1.0.5
+pytest==5.4.3
\ No newline at end of file