<?php use PHPUnit\Framework\TestCase; class Issue2366 { public function foo() { } } class Issue2366Test extends TestCase { /** * @dataProvider provider */ public function testOne($o) { $this->assertEquals(1, $o->foo()); } public function provider() { $o = $this->createMock(Issue2366::class); $o->method('foo')->willReturn(1); return [ [$o], [$o] ]; } }