diff --git a/Dockerfile.tests b/Dockerfile.tests
index fccf8f03..0fda53b5 100644
--- a/Dockerfile.tests
+++ b/Dockerfile.tests
@@ -10,7 +10,7 @@ RUN curl -sSL https://raw.githubusercontent.com/sdispater/poetry/master/get-poet
 
 ADD poetry.lock /tmp
 ADD pyproject.toml /tmp
-RUN cd /tmp && /root/.poetry/bin/poetry update --no-dev
+RUN cd /tmp && /root/.poetry/bin/poetry install
 
 ADD docs/requirements.txt /tmp/requirements-docs.txt
 RUN pip install -r /tmp/requirements-docs.txt
diff --git a/Makefile b/Makefile
index cbf538be..a99e0cec 100644
--- a/Makefile
+++ b/Makefile
@@ -29,7 +29,7 @@ enter-container:
 .PHONY: pytest
 pytest:
 	${DOCKER_COMPOSE} \
-		run nornir py.test --cov=nornir --cov-report=term-missing -vs ${ARGS}
+		run nornir pytest --cov=nornir --cov-report=term-missing -vs ${ARGS}
 
 .PHONY: black
 black:
diff --git a/poetry.lock b/poetry.lock
index 6ba6174d..af7e26ce 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,5 +1,5 @@
 [[package]]
-category = "main"
+category = "dev"
 description = "A small Python module for determining appropriate platform-specific dirs, e.g. a \"user data dir\"."
 name = "appdirs"
 optional = false
@@ -32,7 +32,7 @@ python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
 version = "1.2.1"
 
 [[package]]
-category = "main"
+category = "dev"
 description = "Classes Without Boilerplate"
 name = "attrs"
 optional = false
@@ -60,7 +60,7 @@ cffi = ">=1.1"
 six = ">=1.4.1"
 
 [[package]]
-category = "main"
+category = "dev"
 description = "The uncompromising code formatter."
 name = "black"
 optional = false
@@ -101,7 +101,7 @@ python-versions = "*"
 version = "3.0.4"
 
 [[package]]
-category = "main"
+category = "dev"
 description = "Composable command line interface toolkit"
 name = "click"
 optional = false
@@ -138,6 +138,15 @@ cffi = ">=1.7,<1.11.3 || >1.11.3"
 idna = ">=2.1"
 six = ">=1.4.1"
 
+[[package]]
+category = "main"
+description = "A backport of the dataclasses module for Python 3.6"
+marker = "python_version < \"3.7\""
+name = "dataclasses"
+optional = false
+python-versions = "*"
+version = "0.6"
+
 [[package]]
 category = "dev"
 description = "Better living through Python with decorators"
@@ -344,7 +353,7 @@ version = "5.0.0"
 six = ">=1.0.0,<2.0.0"
 
 [[package]]
-category = "main"
+category = "dev"
 description = "Optional static typing for Python"
 name = "mypy"
 optional = false
@@ -567,6 +576,11 @@ optional = false
 python-versions = ">=3.6"
 version = "0.17"
 
+[package.dependencies]
+[package.dependencies.dataclasses]
+python = "<3.7"
+version = ">=0.6"
+
 [[package]]
 category = "dev"
 description = "Python docstring style checker"
@@ -670,7 +684,7 @@ description = "pytest: simple powerful testing with Python"
 name = "pytest"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
-version = "4.1.0"
+version = "4.1.1"
 
 [package.dependencies]
 atomicwrites = ">=1.0"
@@ -799,7 +813,7 @@ python-versions = "*"
 version = "0.4.1"
 
 [[package]]
-category = "main"
+category = "dev"
 description = "Python Library for Tom's Obvious, Minimal Language"
 name = "toml"
 optional = false
@@ -828,7 +842,7 @@ ipython-genutils = "*"
 six = "*"
 
 [[package]]
-category = "main"
+category = "dev"
 description = "a fork of Python 2 and 3 ast modules with type comment support"
 name = "typed-ast"
 optional = false
@@ -840,8 +854,8 @@ category = "main"
 description = "HTTP library with thread-safe connection pooling, file post, and more."
 name = "urllib3"
 optional = false
-python-versions = "*"
-version = "1.22"
+python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, <4"
+version = "1.24.1"
 
 [[package]]
 category = "dev"
@@ -852,8 +866,8 @@ python-versions = "*"
 version = "0.1.7"
 
 [metadata]
-content-hash = "201b2d64cde04fe470483d97e95d88b2e1b34a9ae420e8e36c0add7a583f7932"
-python-versions = "^3.6,^3.7"
+content-hash = "28f2c2a3dc718279f92ead5d394d9849b84db7479d84559db6542fb51a447404"
+python-versions = ">= 3.6, < 3.8"
 
 [metadata.hashes]
 appdirs = ["9e5896d1372858f8dd3344faf4e5014d21849c756c8d5701f78f8a103b372d92", "d8b24664561d0d34ddfaec54636d502d7cea6e29c3eaf68f3df6180863e2166e"]
@@ -871,6 +885,7 @@ click = ["2335065e6395b9e67ca716de5f7526736bfa6ceead690adf616d925bdc622b13", "5b
 colorama = ["05eed71e2e327246ad6b38c540c4a3117230b19679b875190486ddd2d721422d", "f8ac84de7840f5b9c4e3347b3c1eaa50f7e49c2b07596221daec5edaabbd7c48"]
 coverage = ["06123b58a1410873e22134ca2d88bd36680479fe354955b3579fb8ff150e4d27", "09e47c529ff77bf042ecfe858fb55c3e3eb97aac2c87f0349ab5a7efd6b3939f", "0a1f9b0eb3aa15c990c328535655847b3420231af299386cfe5efc98f9c250fe", "0cc941b37b8c2ececfed341444a456912e740ecf515d560de58b9a76562d966d", "0d34245f824cc3140150ab7848d08b7e2ba67ada959d77619c986f2062e1f0e8", "10e8af18d1315de936d67775d3a814cc81d0747a1a0312d84e27ae5610e313b0", "1b4276550b86caa60606bd3572b52769860a81a70754a54acc8ba789ce74d607", "1e8a2627c48266c7b813975335cfdea58c706fe36f607c97d9392e61502dc79d", "258b21c5cafb0c3768861a6df3ab0cfb4d8b495eee5ec660e16f928bf7385390", "2b224052bfd801beb7478b03e8a66f3f25ea56ea488922e98903914ac9ac930b", "3ad59c84c502cd134b0088ca9038d100e8fb5081bbd5ccca4863f3804d81f61d", "447c450a093766744ab53bf1e7063ec82866f27bcb4f4c907da25ad293bba7e3", "46101fc20c6f6568561cdd15a54018bb42980954b79aa46da8ae6f008066a30e", "4710dc676bb4b779c4361b54eb308bc84d64a2fa3d78e5f7228921eccce5d815", "510986f9a280cd05189b42eee2b69fecdf5bf9651d4cd315ea21d24a964a3c36", "5535dda5739257effef56e49a1c51c71f1d37a6e5607bb25a5eee507c59580d1", "5a7524042014642b39b1fcae85fb37556c200e64ec90824ae9ecf7b667ccfc14", "5f55028169ef85e1fa8e4b8b1b91c0b3b0fa3297c4fb22990d46ff01d22c2d6c", "6694d5573e7790a0e8d3d177d7a416ca5f5c150742ee703f3c18df76260de794", "6831e1ac20ac52634da606b658b0b2712d26984999c9d93f0c6e59fe62ca741b", "71afc1f5cd72ab97330126b566bbf4e8661aab7449f08895d21a5d08c6b051ff", "7349c27128334f787ae63ab49d90bf6d47c7288c63a0a5dfaa319d4b4541dd2c", "77f0d9fa5e10d03aa4528436e33423bfa3718b86c646615f04616294c935f840", "828ad813c7cdc2e71dcf141912c685bfe4b548c0e6d9540db6418b807c345ddd", "859714036274a75e6e57c7bab0c47a4602d2a8cfaaa33bbdb68c8359b2ed4f5c", "85a06c61598b14b015d4df233d249cd5abfa61084ef5b9f64a48e997fd829a82", "869ef4a19f6e4c6987e18b315721b8b971f7048e6eaea29c066854242b4e98d9", "8cb4febad0f0b26c6f62e1628f2053954ad2c555d67660f28dfb1b0496711952", "977e2d9a646773cc7428cdd9a34b069d6ee254fadfb4d09b3f430e95472f3cf3", "99bd767c49c775b79fdcd2eabff405f1063d9d959039c0bdd720527a7738748a", "a5c58664b23b248b16b96253880b2868fb34358911400a7ba39d7f6399935389", "aaa0f296e503cda4bc07566f592cd7a28779d433f3a23c48082af425d6d5a78f", "ab235d9fe64833f12d1334d29b558aacedfbca2356dfb9691f2d0d38a8a7bfb4", "b3b0c8f660fae65eac74fbf003f3103769b90012ae7a460863010539bb7a80da", "bab8e6d510d2ea0f1d14f12642e3f35cefa47a9b2e4c7cea1852b52bc9c49647", "c45297bbdbc8bb79b02cf41417d63352b70bcb76f1bbb1ee7d47b3e89e42f95d", "d19bca47c8a01b92640c614a9147b081a1974f69168ecd494687c827109e8f42", "d64b4340a0c488a9e79b66ec9f9d77d02b99b772c8b8afd46c1294c1d39ca478", "da969da069a82bbb5300b59161d8d7c8d423bc4ccd3b410a9b4d8932aeefc14b", "ed02c7539705696ecb7dc9d476d861f3904a8d2b7e894bd418994920935d36bb", "ee5b8abc35b549012e03a7b1e86c09491457dba6c94112a2482b18589cc2bdb9"]
 cryptography = ["05a6052c6a9f17ff78ba78f8e6eb1d777d25db3b763343a1ae89a7a8670386dd", "0eb83a24c650a36f68e31a6d0a70f7ad9c358fa2506dc7b683398b92e354a038", "0ff4a3d6ea86aa0c9e06e92a9f986de7ee8231f36c4da1b31c61a7e692ef3378", "1699f3e916981df32afdd014fb3164db28cdb61c757029f502cb0a8c29b2fdb3", "1b1f136d74f411f587b07c076149c4436a169dc19532e587460d9ced24adcc13", "21e63dd20f5e5455e8b34179ac43d95b3fb1ffa54d071fd2ed5d67da82cfe6dc", "2454ada8209bbde97065453a6ca488884bbb263e623d35ba183821317a58b46f", "3cdc5f7ca057b2214ce4569e01b0f368b3de9d8ee01887557755ccd1c15d9427", "418e7a5ec02a7056d3a4f0c0e7ea81df374205f25f4720bb0e84189aa5fd2515", "471a097076a7c4ab85561d7fa9a1239bd2ae1f9fd0047520f13d8b340bf3210b", "5ecaf9e7db3ca582c6de6229525d35db8a4e59dc3e8a40a331674ed90e658cbf", "63b064a074f8dc61be81449796e2c3f4e308b6eba04a241a5c9f2d05e882c681", "6afe324dfe6074822ccd56d80420df750e19ac30a4e56c925746c735cf22ae8b", "70596e90398574b77929cd87e1ac6e43edd0e29ba01e1365fed9c26bde295aa5", "70c2b04e905d3f72e2ba12c58a590817128dfca08949173faa19a42c824efa0b", "8908f1db90be48b060888e9c96a0dee9d842765ce9594ff6a23da61086116bb6", "af12dfc9874ac27ebe57fc28c8df0e8afa11f2a1025566476b0d50cdb8884f70", "b4fc04326b2d259ddd59ed8ea20405d2e695486ab4c5e1e49b025c484845206e", "da5b5dda4aa0d5e2b758cc8dfc67f8d4212e88ea9caad5f61ba132f948bab859"]
+dataclasses = ["454a69d788c7fda44efd71e259be79577822f5e3f53f029a22d08004e951dc9f", "6988bd2b895eef432d562370bb707d540f32f7360ab13da45340101bc2307d84"]
 decorator = ["2c51dff8ef3c447388fe5e4453d24a2bf128d3a4c32af3fabef1f01c6851ab82", "c39efa13fbdeb4506c476c9b3babf6a718da943dab7811c206005a4a956c080c"]
 enum34 = ["2d81cbbe0e73112bdfe6ef8576f2238f2ba27dd0d55752a776c41d38b7da2850", "644837f692e5f550741432dd3f223bbb9852018674981b1664e5dc339387588a", "6bd0f6ad48ec2aa117d3d141940d484deccda84d4fcd884f5c3d93c23ecd8c79", "8ad8c4783bf61ded74527bffb48ed9b54166685e4230386a9ed9b1279e2df5b1"]
 flake8-import-order = ["9be5ca10d791d458eaa833dd6890ab2db37be80384707b0f76286ddd13c16cbf", "feca2fd0a17611b33b7fa84449939196c2c82764e262486d5c3e143ed77d387b"]
@@ -919,7 +934,7 @@ pylama = ["7e0327ee9b2a350ed73fe54c240894e534e2bccfb23a59ed5ce89f5a5689ee94", "f
 pynacl = ["05c26f93964373fc0abe332676cb6735f0ecad27711035b9472751faa8521255", "0c6100edd16fefd1557da078c7a31e7b7d7a52ce39fdca2bec29d4f7b6e7600c", "0d0a8171a68edf51add1e73d2159c4bc19fc0718e79dec51166e940856c2f28e", "1c780712b206317a746ace34c209b8c29dbfd841dfbc02aa27f2084dd3db77ae", "2424c8b9f41aa65bbdbd7a64e73a7450ebb4aa9ddedc6a081e7afcc4c97f7621", "2d23c04e8d709444220557ae48ed01f3f1086439f12dbf11976e849a4926db56", "30f36a9c70450c7878053fa1344aca0145fd47d845270b43a7ee9192a051bf39", "37aa336a317209f1bb099ad177fef0da45be36a2aa664507c5d72015f956c310", "4943decfc5b905748f0756fdd99d4f9498d7064815c4cf3643820c9028b711d1", "57ef38a65056e7800859e5ba9e6091053cd06e1038983016effaffe0efcd594a", "5bd61e9b44c543016ce1f6aef48606280e45f892a928ca7068fba30021e9b786", "6482d3017a0c0327a49dddc8bd1074cc730d45db2ccb09c3bac1f8f32d1eb61b", "7d3ce02c0784b7cbcc771a2da6ea51f87e8716004512493a2b69016326301c3b", "a14e499c0f5955dcc3991f785f3f8e2130ed504fa3a7f44009ff458ad6bdd17f", "a39f54ccbcd2757d1d63b0ec00a00980c0b382c62865b61a505163943624ab20", "aabb0c5232910a20eec8563503c153a8e78bbf5459490c49ab31f6adf3f3a415", "bd4ecb473a96ad0f90c20acba4f0bf0df91a4e03a1f4dd6a4bdc9ca75aa3a715", "e2da3c13307eac601f3de04887624939aca8ee3c9488a0bb0eca4fb9401fc6b1", "f67814c38162f4deb31f68d590771a29d5ae3b1bd64b75cf232308e5c74777e0"]
 pynxos = ["2cb462ec8f7f59cd2e12476ddf10e397e26caf78bb3061d1d5d9f7c8d27a649b"]
 pyserial = ["6e2d401fdee0eab996cf734e67773a0143b932772ca8b42451440cfed942c627", "e0770fadba80c31013896c7e6ef703f72e7834965954a78e71a3049488d4d7d8"]
-pytest = ["3e65a22eb0d4f1bdbc1eacccf4a3198bf8d4049dea5112d70a0c61b00e748d02", "5924060b374f62608a078494b909d341720a050b5224ff87e17e12377486a71d"]
+pytest = ["41568ea7ecb4a68d7f63837cf65b92ce8d0105e43196ff2b26622995bb3dc4b2", "c3c573a29d7c9547fb90217ece8a8843aa0c1328a797e200290dc3d0b4b823be"]
 pytest-cov = ["0ab664b25c6aa9716cbf203b17ddb301932383046082c081b9848a0edf5add33", "230ef817450ab0699c6cc3c9c8f7a829c34674456f2ed8df1fe1d39780f7c87f"]
 python-dateutil = ["063df5763652e21de43de7d9e00ccf239f953a832941e37be541614732cdfc93", "88f9287c0174266bb0d8cedd395cfba9c58e87e5ad86b2ce58859bc11be3cf02"]
 pyyaml = ["3d7da3009c0f3e783b2c873687652d83b1bbfd5c88e9813fb7e5b03c0dd3108b", "3ef3092145e9b70e3ddd2c7ad59bdd0252a94dfe3949721633e41344de00a6bf", "40c71b8e076d0550b2e6380bada1f1cd1017b882f7e16f09a65be98e017f211a", "558dd60b890ba8fd982e05941927a3911dc409a63dcb8b634feaa0cda69330d3", "a7c28b45d9f99102fa092bb213aa12e0aaf9a6a1f5e395d36166639c1f96c3a1", "aa7dd4a6a427aed7df6fb7f08a580d68d9b118d90310374716ae90b710280af1", "bc558586e6045763782014934bfaf39d48b8ae85a2713117d16c39864085c613", "d46d7982b62e0729ad0175a9bc7e10a566fc07b224d2c79fafb5e032727eaa04", "d5eef459e30b09f5a098b9cea68bebfeb268697f78d647bd255a085371ac7f3f", "e01d3203230e1786cd91ccfdc8f8454c8069c91bee3962ad93b87a4b2860f537", "e170a9e6fcfd19021dd29845af83bb79236068bf5fd4df3327c1be18182b2531"]
@@ -936,5 +951,5 @@ toml = ["229f81c57791a41d65e399fc06bf0848bab550a9dfd5ed66df18ce5f05e73d5c", "235
 tornado = ["0662d28b1ca9f67108c7e3b77afabfb9c7e87bde174fbda78186ecedc2499a9d", "4e5158d97583502a7e2739951553cbd88a72076f152b4b11b64b9a10c4c49409", "732e836008c708de2e89a31cb2fa6c0e5a70cb60492bee6f1ea1047500feaf7f", "8154ec22c450df4e06b35f131adc4f2f3a12ec85981a203301d310abf580500f", "8e9d728c4579682e837c92fdd98036bd5cdefa1da2aaf6acf26947e6dd0c01c5", "d4b3e5329f572f055b587efc57d29bd051589fb5a43ec8898c77a47ec2fa2bbb", "e5f2585afccbff22390cddac29849df463b252b711aa2ce7c5f3f342a5b3b444"]
 traitlets = ["9c4bd2d267b7153df9152698efb1050a5d84982d3384a37b2c1f7723ba3e7835", "c6cb5e6f57c5a9bdaa40fa71ce7b4af30298fbab9ece9815b5d995ab6217c7d9"]
 typed-ast = ["0555eca1671ebe09eb5f2176723826f6f44cca5060502fea259de9b0e893ab53", "0ca96128ea66163aea13911c9b4b661cb345eb729a20be15c034271360fc7474", "16ccd06d614cf81b96de42a37679af12526ea25a208bce3da2d9226f44563868", "1e21ae7b49a3f744958ffad1737dfbdb43e1137503ccc59f4e32c4ac33b0bd1c", "37670c6fd857b5eb68aa5d193e14098354783b5138de482afa401cc2644f5a7f", "46d84c8e3806619ece595aaf4f37743083f9454c9ea68a517f1daa05126daf1d", "5b972bbb3819ece283a67358103cc6671da3646397b06e7acea558444daf54b2", "6306ffa64922a7b58ee2e8d6f207813460ca5a90213b4a400c2e730375049246", "6cb25dc95078931ecbd6cbcc4178d1b8ae8f2b513ae9c3bd0b7f81c2191db4c6", "7e19d439fee23620dea6468d85bfe529b873dace39b7e5b0c82c7099681f8a22", "7f5cd83af6b3ca9757e1127d852f497d11c7b09b4716c355acfbebf783d028da", "81e885a713e06faeef37223a5b1167615db87f947ecc73f815b9d1bbd6b585be", "94af325c9fe354019a29f9016277c547ad5d8a2d98a02806f27a7436b2da6735", "b1e5445c6075f509d5764b84ce641a1535748801253b97f3b7ea9d948a22853a", "cb061a959fec9a514d243831c514b51ccb940b58a5ce572a4e209810f2507dcf", "cc8d0b703d573cbabe0d51c9d68ab68df42a81409e4ed6af45a04a95484b96a5", "da0afa955865920edb146926455ec49da20965389982f91e926389666f5cf86a", "dc76738331d61818ce0b90647aedde17bbba3d3f9e969d83c1d9087b4f978862", "e7ec9a1445d27dbd0446568035f7106fa899a36f55e52ade28020f7b3845180d", "f741ba03feb480061ab91a465d1a3ed2d40b52822ada5b4017770dfcb88f839f", "fe800a58547dd424cd286b7270b967b5b3316b993d86453ede184a17b5a6b17d"]
-urllib3 = ["06330f386d6e4b195fbfc736b297f58c5a892e4440e54d294d7004e3a9bbea1b", "cc44da8e1145637334317feebd728bd869a35285b93cbb4cca2577da7e62db4f"]
+urllib3 = ["61bf29cada3fc2fbefad4fdf059ea4bd1b4a86d2b6d15e1c7c0b582b9752fe39", "de9529817c93f27c8ccbfead6985011db27bd0ddfcdb2d86f3f663385c6a9c22"]
 wcwidth = ["3df37372226d6e63e1b1e1eda15c594bca98a22d33a23832a90998faa96bc65e", "f4ebe71925af7b40a864553f761ed559b43544f8f71746c2d756c7fe788ade7c"]