Enhance CI with tests (#10)

* Enhance CI

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Add tox.ini

* Fix tests

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

.github/workflows/main.yml

@@ -0,0 +1,26 @@
+name: main
+
+on:
+  push:
+    branches: [main, test-me-*]
+    tags: "*"
+  pull_request:
+
+jobs:
+  main-windows:
+    uses: asottile/workflows/.github/workflows/tox.yml@v1.5.0
+    with:
+      env: '["py38"]'
+      os: windows-latest
+      wheel-tags: true
+  main-macos:
+    uses: asottile/workflows/.github/workflows/tox.yml@v1.5.0
+    with:
+      env: '["py38"]'
+      os: macos-latest
+      wheel-tags: true
+  main-linux:
+    uses: asottile/workflows/.github/workflows/tox.yml@v1.5.0
+    with:
+      env: '["py38"]'
+      os: ubuntu-latest

tox.ini

@@ -0,0 +1,15 @@
+[tox]
+envlist = py,pre-commit
+
+[testenv]
+commands =
+    shfmt --version
+    shfmt --help
+
+[testenv:pre-commit]
+skip_install = true
+deps = pre-commit
+commands = pre-commit run --all-files --show-diff-on-failure
+
+[pep8]
+ignore = E265,E501,W504