PHPUnit不能模拟类

Question

I'm running into an issue where PHPUnit is unable to mock my simple class:

class.php

<?php
    class SUT {
    function doThing() {
        $db = new DB();
        return $db->query();
    }
}

class DB {
    function query() {
        return "failed";
    }
}
?>

test.php

<?php
use PHPUnit\Framework\TestCase;
require 'API/class.php';

class SampleTest extends TestCase {

    public function testTest() {
        $db = $this->createMock(DB::class);
        $db->method('query')
            ->willReturn("win");

        $sut = new SUT();
        $result = $sut->doThing();
        $this->assertEquals("win", $result);
    }

}

Output:

PHPUnit 5.7.21 by Sebastian Bergmann and contributors.
Runtime:       PHP 7.1.16
Configuration: ~/API_tests/config.xml

F...............                                                  16 / 16 (100%)

Time: 604 ms, Memory: 10.00MB
There was 1 failure:

1) SampleTest::testTest
Failed asserting that two strings are equal.
--- Expected
+++ Actual
@@ @@
-'win'
+'failed'

~/API_tests/TestTest.php:14

Am I missing something basic here? Am I required to pass the mock object to the SUT?

Answer 1

This is because you instantiate DB class directly in doNothing method. That means you don'y use the mock you've created. You could use dependency injection to achieve expected result. Just pass DB instance in the SUT::__constructor() as a dependency and it will work.

class.php

class SUT
{
    /** @var DB */
    private $db;

    public function __construct(DB $db) {
        $this->db = $db;
    }

    function doThing()
    {
        return $this->db->query();
    }
}

class DB
{
    function query()
    {
        return "failed";
    }
}

test.php

<?php

use PHPUnit\Framework\TestCase;

require 'API/class.php';

class SampleTest extends TestCase
{

    public function testTest()
    {
        $db = $this->createMock(DB::class);
        $db->method('query')
            ->willReturn("win");

        $sut = new SUT($db);
        $result = $sut->doThing();
        $this->assertEquals("win", $result);
    }

}