CallOrderTest.php

<?php
namespace Test;
use PHPUnit\Framework\TestCase;
interface SystemUnderTest {
    public function first(int $arg): int;
    public function second(string $arg): string;
}
final class CallOrderTest extends TestCase
{
    private $sut;
    protected function setUp(): void
    {
        parent::setUp();
        $this->sut = $this->createMock(SystemUnderTest::class);
        $this->sut
            ->expects(self::once())
            ->method('first')
            ->id('first')
            ->with(1)
            ->willReturn(2);
        $this->sut
            ->expects(self::once())
            ->after('first')
            ->method('second')
            ->with('foo')
            ->willReturn('bar');
    }
    public function testCorrectOrder(): void
    {
        self::assertSame(2, $this->sut->first(1));
        self::assertSame('bar', $this->sut->second('foo'));
    }
    public function testWrongOrder(): void
    {
        self::assertSame('bar', $this->sut->second('foo'));
        self::assertSame(2, $this->sut->first(1));
    }
}