Improve tox/travis configuration

Author: Cito

.travis.yml

@@ -1,25 +1,29 @@
 language: python
 
-dist: xenial
-sudo: true
+matrix:
+  include:
+    - env: TOXENV=black,flake,mypy
+      python: 3.7
+      dist: xenial
+      sudo: true
+    - env: TOXENV=py37
+      python: 3.7
+      dist: xenial
+      sudo: true
+    - env: TOXENV=py36
+      python: 3.6
 
-python:
-    - 3.6
-    - 3.7
+cache:
+  directories:
+    - $HOME/.cache/pip
+    - $TRAVIS_BUILD_DIR/.tox
 
 install:
-    - pip install "poetry==0.12.11"
-    - poetry install
+  - pip install "poetry==0.12.11"
+  - poetry install
 
 script:
-    - flake8 --version
-    - flake8 graphql tests
-    - black --version
-    - black graphql tests --check
-    - mypy --version
-    - mypy graphql
-    - pytest --version
-    - pytest --cov-report term-missing --cov=graphql
+   - tox -e $TOX_ENV -- --cov-report term-missing --cov=graphql
 
 after_success:
-    - codecov
+   - codecov

tox.ini

@@ -1,25 +1,20 @@
 [tox]
 envlist = py{36,37}, black, flake8, mypy
 
-[travis]
-python =
-    3.7: py37
-    3.6: py36
-
 [testenv:black]
-basepython = python3.6
+basepython = python3.7
 deps = black
 commands  =
     black graphql tests --check
 
 [testenv:flake8]
-basepython = python3.6
+basepython = python3.7
 deps = flake8
 commands =
     flake8 graphql tests
 
 [testenv:mypy]
-basepython = python3.6
+basepython = python3.7
 deps = mypy
 commands =
     mypy graphql
@@ -30,7 +25,7 @@ setenv =
 deps =
     pytest
     pytest-asyncio
+    pytest-cov
     pytest-describe
 commands =
-    python -m pip install -U pip
-    pytest {posargs}
+    pytest tests {posargs}