Use GitHub actions for the tests (#381)

* [DO NOT REVIEW] Drop support for outdated PHP versions

https://www.php.net/supported-versions.php

Support for PHP 7.1 and 7.2 remains on a best-effort basis to
accommodate users who haven’t upgraded yet.

* [DO NOT REVIEW] Upgrade PHPUnit to the latest version

@ExpectedException has been replaced with $this->expectException.
assertInternalType was replaced with more specific assertions
(assertIsArray).

* Use GitHub actions for the tests

Travis CI is no longer open-source friendly.

Co-authored-by: Joachim Fritschi <[email protected]>

Author: francoisfreitag

.github/workflows/test.yml

@@ -0,0 +1,41 @@
+name: Test
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        php-version:
+          - php: '7.1'
+            phpunit: '7.5'
+          - php: '7.2'
+            phpunit: '8'
+          - php: '7.3'
+            phpunit: latest
+          - php: '7.4'
+            phpunit: latest
+          - php: '8.0'
+            phpunit: latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: php-actions/composer@v5
+      - name: Run PHPUnit
+        uses: php-actions/phpunit@v2
+        with:
+          version: "${{ matrix.php-version.phpunit }}"
+          php_version: "${{ matrix.php-version.php }}"
+          php_extensions: xdebug
+          args: --verbose --coverage-clover=coverage.xml
+        env:
+          XDEBUG_MODE: coverage
+      - name: Report coverage
+        uses: codecov/codecov-action@v1
+        with:
+          files: coverage.xml