Separate test cases

[biinari]

Make tests more maintainable by separating each example into a separate test function.

Add assertions on the warning / error messages given.

// Assert that the warning messages for $file match those given (and there are no more / fewer warnings).
$this->assertWarningsMatch(
    $file,
    [
        $line => [
            $column => [
                $message
            ]
        ],
    ]
);
// Same for error messages
$this->assertErrorsMatch($file, $messages);