trait MyTrait
{
    public function myTraitMethod()
    {
        return 'my trait method';
    }
}
class MyClass
{
    use MyTrait;
    public function myClassMethod()
    {
        return $this->myTraitMethod();
    }
}
class MyClassTest extends TestCase
{
    public function test_myClassMethod()
    {
        $myMock = new class extends MyClass {
            public function myTraitMethod()
            {
                return 'my mocked method';
            }
        };
        static::assertSame('my mocked method', $myMock->myClassMethod());
    }
}