diff --git a/src/Implementation/Events/StateChanged.php b/src/Implementation/Events/StateChanged.php
index 54cafab..f12003a 100644
--- a/src/Implementation/Events/StateChanged.php
+++ b/src/Implementation/Events/StateChanged.php
@@ -28,4 +28,17 @@ public function getOldState(): StateInterface
     {
         return $this->oldState;
     }
+
+    public function __toString(): string
+    {
+        $item = $this->getItem();
+
+        return sprintf(
+            '%s[%s, %s->%s]',
+            __CLASS__,
+            method_exists($item, '__toString') ? $item : get_class($item),
+            $this->getOldState(),
+            $item->getState()
+        );
+    }
 }
diff --git a/src/Implementation/Events/StateChanging.php b/src/Implementation/Events/StateChanging.php
index 9ff372c..ee0f916 100644
--- a/src/Implementation/Events/StateChanging.php
+++ b/src/Implementation/Events/StateChanging.php
@@ -28,4 +28,17 @@ public function getNewState(): StateInterface
     {
         return $this->newState;
     }
+
+    public function __toString(): string
+    {
+        $item = $this->getItem();
+
+        return sprintf(
+            '%s[%s, %s->%s]',
+            __CLASS__,
+            method_exists($item, '__toString') ? $item : get_class($item),
+            $item->getState(),
+            $this->getNewState()
+        );
+    }
 }
diff --git a/src/Implementation/Traits/Plantable.php b/src/Implementation/Traits/Plantable.php
index 50e4b47..d3d8299 100644
--- a/src/Implementation/Traits/Plantable.php
+++ b/src/Implementation/Traits/Plantable.php
@@ -14,26 +14,25 @@ trait Plantable
 {
     public function toPlantUML(): string
     {
-        /** @var $this TransitionRepositoryInterface */
-        return implode(PHP_EOL, array_merge(
-            ['@startuml', ''],
-            array_map(
-                static function (TransitionInterface $transition): string {
-                    $oldState = $transition->getOldState();
-                    $newState = $transition->getNewState();
-                    $oldText = $oldState instanceof DescribableInterface ? $oldState->getDescription() : $oldState->getName();
-                    $newText = $newState instanceof DescribableInterface ? $newState->getDescription() : $newState->getName();
+        $generateNodesAndEdges = static function (TransitionInterface $transition): string {
+            $oldText = ($oldState = $transition->getOldState()) instanceof DescribableInterface
+                ? $oldState->getDescription() : $oldState->getName();
+            $newText = ($newState = $transition->getNewState()) instanceof DescribableInterface
+                ? $newState->getDescription() : $newState->getName();
+
+            $result = "($oldText) --> ($newText)";
 
-                    $result = "($oldText) --> ($newText)";
+            if ($transition instanceof DescribableInterface) {
+                $result .= " : {$transition->getDescription()}";
+            }
 
-                    if ($transition instanceof DescribableInterface) {
-                        $result .= " : {$transition->getDescription()}";
-                    }
+            return $result;
+        };
 
-                    return $result;
-                },
-                iterator_to_array($this)
-            ),
+        /** @var $this TransitionRepositoryInterface */
+        return implode(PHP_EOL, array_merge(
+            ['@startuml', ''],
+            array_map($generateNodesAndEdges, iterator_to_array($this)),
             ['', '@enduml']
         ));
     }
diff --git a/tests/BuilderTest.php b/tests/BuilderTest.php
index 055c461..836c1e7 100644
--- a/tests/BuilderTest.php
+++ b/tests/BuilderTest.php
@@ -50,15 +50,7 @@ public function test_that_new_state_must_be_declared_before_transitions(): void
 
     public function test_that_transitioning_with_mutator_works(): void
     {
-        $this->expectNotToPerformAssertions();
-
-        $engine = Builder::create()
-            ->defState('a')
-            ->defState('b')
-            ->defTransition('a', 'b')
-            ->getEngine();
-
-        $item = new StatefulItem(new State('a'));
+        $item = new StatefulItem(new State('started'));
         $mutator = Builder::makeStateMutator(
             static function () use ($item): State {
                 return $item->getState();
@@ -68,6 +60,8 @@ static function (State $newState) use ($item): void {
             }
         );
 
-        $engine->changeState($mutator, new State('b'));
+        $this->builder->getEngine()->changeState($mutator, new State('finished'));
+
+        $this->assertSame('finished', $item->getState()->getName());
     }
 }
diff --git a/tests/EventTest.php b/tests/EventTest.php
index 0c81511..588c900 100644
--- a/tests/EventTest.php
+++ b/tests/EventTest.php
@@ -6,11 +6,7 @@
 use Psr\EventDispatcher\EventDispatcherInterface;
 use uuf6429\StateEngine\Implementation\Builder;
 use uuf6429\StateEngine\Implementation\Entities\State;
-use uuf6429\StateEngine\Implementation\Events\StateChanged;
-use uuf6429\StateEngine\Implementation\Events\StateChanging;
 use uuf6429\StateEngine\Interfaces\EngineInterface;
-use uuf6429\StateEngine\Interfaces\StateAwareInterface;
-use uuf6429\StateEngine\Interfaces\StateInterface;
 
 class EventTest extends TestCase
 {
@@ -32,7 +28,7 @@ protected function setUp(): void
             ->getEngine($this->dispatcher);
     }
 
-    public function test_that_engine_fires_exception(): void
+    public function test_that_engine_triggers_events(): void
     {
         $dispatchedEvents = [];
         $this->dispatcher
@@ -43,30 +39,16 @@ public function test_that_engine_fires_exception(): void
         $startedState = new State('started');
         $finishedState = new State('finished');
 
-        $statefulItem = new class implements StateAwareInterface {
-            public StateInterface $state;
-
-            public function getState(): StateInterface
-            {
-                return $this->state;
-            }
-
-            public function setState(StateInterface $newState): void
-            {
-                $this->state = $newState;
-            }
-        };
-
-        $statefulItem->state = $startedState;
+        $statefulItem = new StatefulItem($startedState);
         $this->engine->changeState($statefulItem, $finishedState);
 
-        $this->assertEquals($finishedState, $statefulItem->state);
+        $this->assertEquals($finishedState, $statefulItem->getState());
         $this->assertEquals(
             [
-                new StateChanging($statefulItem, $finishedState),
-                new StateChanged($statefulItem, $startedState),
+                'uuf6429\StateEngine\Implementation\Events\StateChanging[StatefulItem, finished->finished]',
+                'uuf6429\StateEngine\Implementation\Events\StateChanged[StatefulItem, started->finished]',
             ],
-            $dispatchedEvents
+            array_map('strval', $dispatchedEvents)
         );
     }
 }
diff --git a/tests/JiraIssueTest.php b/tests/JiraIssueTest.php
index 78d65e8..a9d8a4b 100644
--- a/tests/JiraIssueTest.php
+++ b/tests/JiraIssueTest.php
@@ -81,10 +81,11 @@ static function (TransitionInterface $transition) {
 
     public function test_that_transitioning_from_in_dev_to_ready_for_qa_is_allowed(): void
     {
-        $this->expectNotToPerformAssertions();
-
         $item = new StatefulItem(new State('in-dev'));
+
         $this->engine->changeState($item, new State('ready-for-qa'));
+
+        $this->assertSame('ready-for-qa', $item->getState()->getName());
     }
 
     public function test_that_transitioning_from_in_dev_to_in_qa_is_not_allowed(): void
@@ -92,6 +93,7 @@ public function test_that_transitioning_from_in_dev_to_in_qa_is_not_allowed(): v
         $this->expectExceptionMessage('Cannot apply transition "in-dev -> in-qa"; no such transition was defined.');
 
         $item = new StatefulItem(new State('in-dev'));
+
         $this->engine->changeState($item, new State('in-qa'));
     }
 
diff --git a/tests/StatefulItem.php b/tests/StatefulItem.php
index 6944aa1..38c45de 100644
--- a/tests/StatefulItem.php
+++ b/tests/StatefulItem.php
@@ -23,4 +23,9 @@ public function setState(StateInterface $newState): void
     {
         $this->state = $newState;
     }
+
+    public function __toString(): string
+    {
+        return 'StatefulItem';
+    }
 }