Add unittest example

.gitlab-ci.yml

+stages:
+  - unit-tests
+  - integration-tests
+
+# Unit Tests #
+unit-tests:
+  stage: unit-tests
+  tags:
+    - php72
+  variables:
+    EXECUTOR_SUITE: project-unit
+  before_script:
+    - ~/.composer/vendor/met/test-executor/run.sh setup
+  script:
+    - ~/.composer/vendor/met/test-executor/run.sh tests
+  after_script:
+    - ~/.composer/vendor/met/test-executor/run.sh cleanup
+
+# Integration Tests #
+integration-tests:
+  stage: integration-tests
+  tags:
+    - php72
+  variables:
+    EXECUTOR_SUITE: project-integration
+  before_script:
+    - ~/.composer/vendor/met/test-executor/run.sh setup
+  script:
+    - ~/.composer/vendor/met/test-executor/run.sh tests
+  after_script:
+    - ~/.composer/vendor/met/test-executor/run.sh cleanup

phpunit.unit.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+-->
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/6.2/phpunit.xsd"
+         colors="true"
+         columns="max"
+         beStrictAboutTestsThatDoNotTestAnything="false"
+         bootstrap="src/dev/tests/unit/framework/bootstrap.php"
+>
+    <testsuite name="MET Unit Tests">
+        <directory suffix="Test.php">src/app/code/Met/*/Test/Unit</directory>
+    </testsuite>
+    <php>
+        <ini name="date.timezone" value="America/Los_Angeles"/>
+        <ini name="xdebug.max_nesting_level" value="200"/>
+    </php>
+    <listeners>
+        <listener class="Magento\Framework\TestFramework\Unit\Listener\ReplaceObjectManager"/>
+    </listeners>
+    <!-- Code Coverage Whitelist -->
+    <filter>
+        <whitelist processUncoveredFilesFromWhitelist="true">
+            <directory suffix=".php">src/app/code/Met/*</directory>
+            <exclude>
+                <directory suffix=".php">src/app/code/Magento</directory>
+                <directory suffix=".php">src/app/code/Met/*/Test</directory>
+                <directory suffix="registration.php">src/app/code/*/*</directory>
+            </exclude>
+        </whitelist>
+    </filter>
+</phpunit>