Add tox tests & coveralls github action

This commit essentially adds back tests to our CI pipeline. They were
previously dropped due to Travis pricing policy change.

This workflow utilizes a few interesting projects to make this action
easier to maintain such as the coveralls github action
(https://github.com/marketplace/actions/coveralls-github-action)
and the tox-gh-actions project
(https://github.com/ymyzk/tox-gh-actions)

.github/workflows/tests.yml

@@ -0,0 +1,55 @@
+name: Tox tests and Coveralls
+on: pull_request
+jobs:
+    run_tests:
+        runs-on: ubuntu-latest
+        strategy:
+            fail-fast: false
+            matrix:
+                python-version: [3.6, 3.7, 3.8, 3.9, pypy-3.7]
+
+        steps:
+            - name: Checkout repository
+              uses: actions/checkout@v2
+
+            - name: Set up Python ${{ matrix.python-version }}
+              uses: actions/setup-python@v2
+              with:
+                  python-version: ${{ matrix.python-version }}
+
+            - name: Install dependencies
+              run: |
+                  python -m pip install --upgrade pip
+                  pip install tox tox-gh-actions
+
+            - name: Test with tox
+              run: tox
+
+    coverage_report:
+        needs: run_tests
+        runs-on: ubuntu-latest
+        steps:
+            - name: Checkout repository
+              uses: actions/checkout@v2
+
+            - name: Install dependencies
+              run: |
+                  python -m pip install --upgrade pip
+                  pip install coverage docopt yarg requests
+
+            - name: Calculate coverage
+              run: coverage run --source=pipreqs -m unittest discover
+
+            - name: Create XML report
+              run: coverage xml
+
+            - name: Upload coverage to Codecov
+              uses: codecov/codecov-action@v2
+              with:
+                  files: coverage.xml
+                  fail_ci_if_error: true
+
+            # - name: Compile and submit coveralls report
+            #   uses: coverallsapp/github-action@master
+            #   with:
+            #       github-token: ${{ secrets.github_token }}

README.rst

@@ -10,9 +10,8 @@
         :target: https://pypi.python.org/pypi/pipreqs
 
 
-.. image:: https://img.shields.io/coveralls/bndr/pipreqs.svg
-        :target: https://coveralls.io/r/bndr/pipreqs
-
+.. image:: https://codecov.io/gh/bndr/pipreqs/branch/master/graph/badge.svg?token=0rfPfUZEAX
+        :target: https://codecov.io/gh/bndr/pipreqs
 
 .. image:: https://img.shields.io/pypi/l/pipreqs.svg
         :target: https://pypi.python.org/pypi/pipreqs

tox.ini

@@ -1,6 +1,14 @@
 [tox]
 envlist = py36, py37, py38, py39, pypy3, flake8
 
+[gh-actions]
+python =
+    3.6: py36
+    3.7: py37
+    3.8: py38
+    3.9: py39
+    pypy-3.7: pypy3
+
 [testenv]
 setenv =
     PYTHONPATH = {toxinidir}:{toxinidir}/pipreqs