test.php

<?php
abstract class Foo
{
    protected $records;

    public function __construct()
    {
        $this->records = $this->setRecords();
    }

    abstract public function setRecords();

    public function getMaxRecord()
    {
        return max($this->records);
    }
}

//tests
class FooTest extends PHPUnit_Framework_TestCase
{
    public function test___construct()
    {
        //arrange
        $vale = 'test_value';
        $foo = $this
            ->getMockBuilder(Foo::class)
            ->setMethods(array('setRecords'))
            ->disableOriginalConstructor()
            ->getMockForAbstractClass();
        $foo
            ->expects($this->once())
            ->method('setRecords')
            ->willReturn($value);        
        $class = new ReflectionClass(Foo::class);        
        $constructor = $class->getConstructor();
        
        //act
        $constructor->invoke($foo);
        
        //assert
        $this->assertEquals($value, $this->getObjectAttribute($foo, 'records'));
    }
}