public function testMergeA() { $collection1 = new Collection(['a' => 'a', 'b' => 'b']); $collection2 = new Collection(['a' => 'a', 'c' => 'c']); $collection3 = new Collection(['a' => 'a', 'e' => 'e']); $result = $collection1->mergeA($collection2, $collection3); $this->assertNotSame($collection1, $result); $this->assertInstanceOf(get_class($collection1), $result); $this->assertSame(['a' => 'a', 'b' => 'b', 'c' => 'c', 'e' => 'e'], (array) $result); }