Add test case

Author: hirokinoue

test/VariableParserTest.php

@@ -107,7 +107,7 @@ public function testParseAssignOperator(): void
         $functions = $result->functions;
         $this->assertCount(1, $functions);
         $this->assertSame('assignFunction', $functions[0]->name);
-        $this->assertCount(14, $functions[0]->getVariables());
+        $this->assertCount(15, $functions[0]->getVariables());
 
         $vars = $functions[0]->getVariables();
         $this->assertSame('num', $vars[0]->name);
@@ -152,6 +152,9 @@ public function testParseAssignOperator(): void
         $this->assertSame('num', $vars[13]->name);
         $this->assertSame(18, $vars[13]->lineNumber);
         $this->assertSame(true, $vars[13]->assigned);
+        $this->assertSame('num', $vars[14]->name);
+        $this->assertSame(19, $vars[14]->lineNumber);
+        $this->assertSame(true, $vars[14]->assigned);
     }
 
     public function testInterpolatedStringFunction(): void

test/fixtures/assign_operator.php

@@ -16,4 +16,5 @@ function assignFunction(): void
     $num >>= 1; // 16行目
     $num .= 1; // 17行目
     $num ??= 1; // 18行目
+    $num =& f(); // 19行目
 }