As reported in https://github.com/sebastianbergmann/php-code-coverage/issues/411#issuecomment-254048381 :

In some unknown conditions, the executable lines are not fully returned.

It's pretty difficult to reproduce the issue in a very small amount of code, here's what I've seen using var_dump in php-code-coverage code:

In some case (when it works as expected), here's the kind of code coverage data reported by Xdebug:

{
    "36": [
        "Bundle\\MyBundle\\Tests\\Controller\\Debug\\MyAccountControllerTest::testAccountIndex"
    ],
    "37": null,
    "49": [],
    "51": [],
    "52": [],
    "56": [],
    "58": null,
    "70": [],
    "71": null,
    "83": [],
    "84": null,
    "101": [],
    "102": [],
    "105": [],
    "107": [],
    "108": [],
    "110": [],
    "111": [],
    "112": [],
    "113": [],
    "114": [],
    "115": [],
    "116": [],
    "118": null
}

However, when the same test is run in the test suite, here's the code coverage data reported by xdebug:

array(2) {
  [36] =>
  array(1) {
    [0] =>
    string(87) "Bundle\MyBundle\Tests\Controller\Debug\MyAccountControllerTest::testAccountIndex"
  }
  [37] =>
  NULL
}

I hope it would help @derickr to solve the issue. In the meantime, I'm continuing to try to find a small reproducer