Prevent skill sets from sharing their skills

Each SkillSet should provide his own skills and should not share the
skills with other skill sets.
Therefore use an instance property instead of static.

src/Entity/SkillSet.php

@@ -30,6 +30,11 @@ class SkillSet
      */
     private $data;
 
+    /**
+     * @var array
+     */
+    private $skills = [];
+
     private function __construct(array $data)
     {
         $this->data = $data;
@@ -55,17 +60,15 @@ class SkillSet
      */
     public function getSkills(): array
     {
-        static $skills = [];
+        if ($this->skills !== []) {
-
+            return $this->skills;
-        if ($skills !== []) {
-            return $skills;
         }
 
         foreach ($this->data['skills'] as $skill) {
-            $skills[] = Skill::createFromJson(json_encode($skill));
+            $this->skills[] = Skill::createFromJson(json_encode($skill));
         }
 
-        return $skills;
+        return $this->skills;
     }
 
     public function toArray(): array

tests/Unit/Entity/SkillSetTest.php

@@ -101,6 +101,18 @@ class SkillSetTest extends TestCase
         static::assertSame($skillsFirstCall, $skillsSecondCall);
     }
 
+    /**
+     * @test
+     */
+    public function twoDifferentInstancesProvideTheirOwnSkills()
+    {
+        $subject1 = SkillSet::createFromJson('{"skills":[{"uid":90,"title":"Example title 1"},{"goals":"<p>Example goals</p>","uid":91,"title":"Example title 2"}]}');
+        $subject2 = SkillSet::createFromJson('{"skills":[{"uid":80,"title":"Example title 10"},{"goals":"<p>Example goals</p>","uid":81,"title":"Example title 11"}]}');
+
+        static::assertSame(90, $subject1->getSkills()[0]->getId());
+        static::assertSame(80, $subject2->getSkills()[0]->getId());
+    }
+
     /**
      * @test
      */