psalm/tests/InterfaceTest.php

<?php
namespace Psalm\Tests;

use PhpParser\ParserFactory;
use PHPUnit_Framework_TestCase;
use Psalm\Checker\FileChecker;
use Psalm\Config;
use Psalm\Context;

class InterfaceTest extends PHPUnit_Framework_TestCase
{
    protected static $parser;

    public static function setUpBeforeClass()
    {
        self::$parser = (new ParserFactory)->create(ParserFactory::PREFER_PHP7);

        $config = Config::getInstance();
        $config->throw_exception = true;
        $config->use_docblock_types = true;
    }

    public function setUp()
    {
        FileChecker::clearCache();
    }

    public function testExtends()
    {
        $stmts = self::$parser->parse('<?php
        interface A
        {
            /**
             * @return string
             */
            public function foo();
        }

        interface B
        {
            public function bar() {

            }
        }

        interface C extends A, B
        {
            /**
             * @return string
             */
            public function baz() {

            }
        }

        class D implements C
        {
            public function foo()
            {
            }

            public function bar()
            {
            }

            public function baz()
            {
            }
        }

        function qux(A $a) {

        }

        $cee = (new D())->baz();
        $dee = (new D())->foo();
        qux(new D());
        ?>
        ');

        $file_checker = new FileChecker('somefile.php', $stmts);
        $context = new Context('somefile.php');
        $file_checker->check(true, true, $context);
        $this->assertEquals('string', (string) $context->vars_in_scope['$cee']);
        $this->assertEquals('string', (string) $context->vars_in_scope['$dee']);
    }
}