Reach psalm level 2

The error about using deprecated PHPUnit APIs are put in baseline as
this code is necessary to support multiple PHPUnit versions.

composer.json

@@ -12,6 +12,7 @@
         "phpstan/phpstan": "1.4.10 || 1.10.15",
         "phpstan/phpstan-phpunit": "^1.0",
         "phpunit/phpunit": "^7.5 || ^8.5 || ^9.5",
+        "psalm/plugin-phpunit": "0.18.4",
         "psr/log": "^1 || ^2 || ^3",
         "vimeo/psalm": "4.30.0 || 5.12.0"
     },

psalm-baseline.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<files psalm-version="5.12.0@f90118cdeacd0088e7215e64c0c99ceca819e176">
+  <file src="tests/Doctrine/Deprecations/DeprecationTest.php">
+    <DeprecatedMethod>
+      <code>parent::expectDeprecation()</code>
+      <code>parent::expectDeprecationMessage($message)</code>
+    </DeprecatedMethod>
+  </file>
+</files>

psalm.xml

@@ -1,12 +1,13 @@
 <?xml version="1.0"?>
 <psalm
-    errorLevel="3"
+    errorLevel="2"
     resolveFromConfigFile="true"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="https://getpsalm.org/schema/config"
     xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
     findUnusedBaselineEntry="true"
     findUnusedCode="false"
+    errorBaseline="psalm-baseline.xml"
 >
     <projectFiles>
         <directory name="lib/Doctrine/Deprecations" />
@@ -15,4 +16,7 @@
             <directory name="vendor" />
         </ignoreFiles>
     </projectFiles>
+    <plugins>
+        <pluginClass class="Psalm\PhpUnitPlugin\Plugin"/>
+    </plugins>
 </psalm>