Mocking json_decode

[markmontes17]

Is it possible to use the mocked json_decode for unit testing SomeClass::someMethod?
Where in someMethod() contains json_decode?

Summarized code snippet:

test Method:
PHPMockery::mock(NAMESPACE, "json_decode")
->andReturn("test");

$classMock = new SomeClass();
$actual = $classMock->someMethod();
$this->assertEquals("test", $actual);

SomeClass::someMethod:
// codes here
$var = json_decode($str);
// codes here

[joskfg]

$classMock = new SomeClass();
PHPMockery::mock(dirname($classMock::class), "json_decode")->andReturn("test");

$actual = $classMock->someMethod();
$this->assertEquals("test", $actual);