Method was expected to be called 1 times, actually called 0 times.

[bartonhammond]

The "mail" built in function is not getting mocked...Not sure what I'm missing.

Test case:

<?php

namespace Tests;
require_once __DIR__ . "/../../utilities/Util.php";

class UtilTest extends \PHPUnit\Framework\TestCase {
    use \phpmock\phpunit\PHPMock;
 
    public function testReportError()
    {

        $mail = $this->getFunctionMock(__NAMESPACE__, "mail");

        $mail->expects($this->once())
            ->willReturnCallback(
                function ($email, $subject, $body) {
                    print 'inside callback';
                    var_dump($email);
                    var_dump($subject);
                    var_dump($body);
                    $this->assertEquals("mdahlke@wisnet.com", $email);
                    $output = ["failure"];
                    $return_var = 1;
                }
            );

        $result = \Util::reportError('testReportErrorWithNoSubjectSendEmailFails', 'testArg', 'Testing reporting errors', ['subject' => 'test']);

    }
}

SUT Util.php

 public static function reportError($mailArgs = []) {
       print("\nready to call mail");
        $result = mail($mailArgs['email'], $mailArgs['subject'], $mailArgs['body']);
        print("\nresult " . $result);

        return $result;
}

Output
composer test

phpunit --colors=always
PHPUnit 5.7.23 by Sebastian Bergmann and contributors.

F 1 / 1 (100%)
ready to call mail

result 1

Time: 59 ms, Memory: 5.00MB

There was 1 failure:

1. Tests\UtilTest::testReportError
   Expectation failed for method name is equal to string:delegate when invoked 1 time(s).
   Method was expected to be called 1 times, actually called 0 times.

FAILURES!
Tests: 1, Assertions: 1, Failures: 1.

[bartonhammond]

Argh...just realized the SUT and Testcase both have to share the same namespace...

[henryobiaraije]

Yes, that is correct.
If the SUT is in a different namespace, you can dynamically get the namespace using PHP ReflectionClass.
See here https://stackoverflow.com/a/67696809/6909825