[TASK] Add a PHPUnit example configuration file (#16)

.travis.yml

@@ -62,6 +62,11 @@ script:
   echo "Running the unit tests";
   composer ci:tests:unit;
 
+- >
+  echo;
+  echo "Running the model tests";
+  .Build/vendor/bin/phpunit -c Configuration/PHPUnit/ModelTests.xml;
+
 - >
   echo;
   echo "Running the functional tests";

Configuration/PHPUnit/ModelTests.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/6.5/phpunit.xsd"
+         backupGlobals="true"
+         backupStaticAttributes="false"
+         bootstrap="../../.Build/vendor/nimut/testing-framework/res/Configuration/UnitTestsBootstrap.php"
+         colors="true"
+         convertErrorsToExceptions="true"
+         convertWarningsToExceptions="true"
+         forceCoversAnnotation="false"
+         processIsolation="false"
+         stopOnError="false"
+         stopOnFailure="false"
+         stopOnIncomplete="false"
+         stopOnSkipped="false"
+         verbose="false"
+>
+    <testsuites>
+        <testsuite name="Model unit tests">
+            <directory>../../Tests/Unit/Domain/Model</directory>
+        </testsuite>
+    </testsuites>
+</phpunit>

README.md

@@ -58,6 +58,12 @@ In the Run configurations, copy the PHPUnit configuration and use these settings
 - [x] Use alternative configuration file
 - use `.Build/vendor/nimut/testing-framework/res/Configuration/FunctionalTests.xml`
 
+### Example PHPUnit configuration file with a test suite
+
+The file [`Configuration/PHPUnit/ModelTests.xml`](Configuration/PHPUnit/ModelTests.xml)
+contains an example of a PHPUnit configuration file that has a test suite
+(based on the unit tests configuration file from the testing framework).
+
 ## Creating new extensions with automated tests
 
 For creating new extensions, I recommend taking