Add MLP partial train test after restore from file (#243)

tests/Classification/MLPClassifierTest.php

@@ -193,6 +193,35 @@ public function testSaveAndRestore(): void
         $this->assertEquals($predicted, $restoredClassifier->predict($testSamples));
     }
 
+    public function testSaveAndRestoreWithPartialTraining(): void
+    {
+        $network = new MLPClassifier(2, [2], ['a', 'b'], 1000);
+        $network->partialTrain(
+            [[1, 0], [0, 1]],
+            ['a', 'b']
+        );
+
+        $this->assertEquals('a', $network->predict([1, 0]));
+        $this->assertEquals('b', $network->predict([0, 1]));
+
+        $filename = 'perceptron-test-'.random_int(100, 999).'-'.uniqid();
+        $filepath = tempnam(sys_get_temp_dir(), $filename);
+        $modelManager = new ModelManager();
+        $modelManager->saveToFile($network, $filepath);
+
+        /** @var MLPClassifier $restoredNetwork */
+        $restoredNetwork = $modelManager->restoreFromFile($filepath);
+        $restoredNetwork->partialTrain(
+            [[1, 1], [0, 0]],
+            ['a', 'b']
+        );
+
+        $this->assertEquals('a', $restoredNetwork->predict([1, 0]));
+        $this->assertEquals('b', $restoredNetwork->predict([0, 1]));
+        $this->assertEquals('a', $restoredNetwork->predict([1, 1]));
+        $this->assertEquals('b', $restoredNetwork->predict([0, 0]));
+    }
+
     public function testThrowExceptionOnInvalidLayersNumber(): void
     {
         $this->expectException(InvalidArgumentException::class);