PHP Unit Test PHPUnit, how to mock class to invoke its own method?

PHPUnit Unit Test Phplaravel5

When using LARAVEL5 to do unit tests, you need to test querysessionidtest this method when you encounter the following problems.
But you need to mock out sessionidtest This method, the specific code is as follows:
Classes are as follows:

class ZabbixSystem implements ApmSystemInterface      public function querySessionIdTest()    {        echo 'querySessionIdTest';        return $this->sessionidtest();    }    public function sessionidtest()    {        echo 'sessionidtest';        return 'aaa';    }}

Unit test Method:

public function testQuerySessionIdSuccess()    {        $return = 'aaa';        $stub = Mockery::mock('mcokname');//        $this->app->instance('ZabbixSystem', $stub);        $stub->shouldReceive('querySessionIdTest')->andReturn($return);        $response = $stub->querySessionIdTest();        $this->assertEquals('aaa', $response);    }    public function testQuerySession()    {        // 为 SomeClass 类创建桩件。        $stub = $this->getMockBuilder('App\Services\ZabbixSystem')->setMethods(array(            'querySessionIdTest',            'sessionidtest'        ))->getMock();        // 配置桩件。        $stub->method('sessionidtest')->willReturn('111');        $this->app->instance('ZabbixSystem', $stub);        $this->assertEquals('foo', $stub->querySessionIdTest());    }

There are two ways to test, but none are successful, and I want the result:
Echo ' Querysessionidtest ';
And then the test succeeds.

