Fix Formatters::valueToString when is an array

Signed-off-by: davidarendsen <davidarendsen@hey.com>

src/Formatters.php

@@ -16,7 +16,7 @@ class Formatters {
         }
         elseif(is_array($value))
         {
-            return self::toFluxArrayString($value);
+            return '[' . self::toFluxArrayString($value) . ']';
         }
 
         return $value;

src/Function/Group.php

@@ -24,7 +24,12 @@ class Group extends Base {
 
     public function __toString()
     {
-        return '|> group(columns: [' . Formatters::toFluxArrayString($this->columns) . '], mode: "' . $this->mode . '") ';
+        $array = Formatters::toFluxArrayString([
+            'columns' => $this->columns,
+            'mode' => $this->mode,
+        ]);
+
+        return '|> group(' . $array . ') ';
     }
 
 }

tests/FormattersTest.php

@@ -0,0 +1,21 @@
+<?php
+declare(strict_types=1);
+
+use Arendsen\FluxQueryBuilder\Formatters;
+use PHPUnit\Framework\TestCase;
+
+final class FormattersTest extends TestCase {
+
+    public function testAssociativeArrayNested()
+    {
+        $array = [
+            'columns' => ['foo', 'bar'],
+            'mode' => 'by'
+        ];
+
+        $expected = 'columns: ["foo", "bar"], mode: "by"';
+
+        $this->assertEquals($expected, Formatters::toFluxArrayString($array));
+    }
+
+}