dml_test.php

<?php
class core_dml_testcase extends database_driver_testcase {
    /**
     * Test the database instrumentation as SQL comment.
     */
    public function test_instrument_sql() {
        global $CFG;

        require_once($CFG->dirroot . '/lib/tests/fixtures/test_dml_instrumentation_fixture.php');
        $fixture = new \core\test_dml_instrumentation_fixture($this);

        $sql = "SELECT * FROM {users}";

        $CFG->debugsqltrace = 0;
        $out = $fixture->four($sql);
        $this->assertEquals("SELECT * FROM {users}", $out);

        $CFG->debugsqltrace = 1;
        $out = $fixture->four($sql);
        $expected = <<<EOD
SELECT * FROM {users}
-- line 22 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->one()
EOD;
        $this->assertEquals($expected, $out);

        $CFG->debugsqltrace = 2;
        $out = $fixture->four($sql);
        $expected = <<<EOD
SELECT * FROM {users}
-- line 22 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->one()
-- line 26 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->two()
EOD;
        $this->assertEquals($expected, $out);

        $CFG->debugsqltrace = 10;
        $out = $fixture->recurse($sql, 9);
        $expected = <<<EOD
SELECT * FROM {users}
-- line 35 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->one()
-- line 37 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->recurse()
-- line 37 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->recurse()
-- line 37 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->recurse()
-- line 37 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->recurse()
-- line 37 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->recurse()
-- line 37 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->recurse()
-- line 37 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->recurse()
-- line 37 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->recurse()
-- line 37 of /lib/tests/fixtures/test_dml_instrumentation_fixture.php: call to core\\test_dml_instrumentation_fixture->recurse()
EOD;
        $this->assertEquals($expected, $out);
    }

test_dml_instrumentation_fixture.php

<?php

namespace core;

class test_dml_instrumentation_fixture {
    private $db;

    public function __construct($testcase) {
        $this->db = $testcase->getMockBuilder(\moodle_database::class)
            ->getMockForAbstractClass();
    }

    public function get_mock() {
        return $this->db;
    }

    public function one(string $sql) {
        return $this->db->instrument_sql($sql, debug_backtrace(2));
    }

    public function two(string $sql) {
        return $this->one($sql);
    }

    public function three(string $sql) {
        return $this->two($sql);
    }

    public function four(string $sql) {
        return $this->three($sql);
    }

    public function recurse(string $sql, int $count = 5) {
        if ($count === 0) {
            return $this->one($sql);
        } else {
            return $this->recurse($sql, $count - 1);
        }
    }
}