Wanted to try my hand a mocking the PHP Google API. Am I doing this right?

GoogleMailRepositoryTest.php

<?php

namespace Tests\Unit;

use Tests\TestCase;

class GoogleMailRepositoryTest extends TestCase
{
    public function testFindsMessage()
    {
        $mGoogle_Service_Gmail = $this->createMock(\Google_Service_Gmail::class);
        $mGoogle_Service_Gmail->users_messages =
            tap($this->createMock(\Google_Service_Gmail_Resource_UsersMessages::class), function($mock) {

                $mGoogle_service_GmailMessage = tap($this->createMock(\Google_Service_Gmail_Message::class), function($mock) {
                    $mock->method('getId')->willReturn('123456789');

                    $mock->method('getPayload')->willReturn(
                        tap($this->createMock(\Google_Service_Gmail_MessagePart::class), function($mock) {
                            $mock->method('getBody')->willReturn(
                                tap($this->createMock(\Google_Service_Gmail_MessagePartBody::class), function($mock) {
                                    $mock->method('getData')->willReturn(
                                        strtr(base64_encode('Body for message 123456789'), '+/', '-_')
                                    );
                                })
                            );
                        })
                    );
                });

                $mock->method('listUsersMessages')->willReturn(
                    tap($this->createMock(\Google_Service_Gmail_ListMessagesResponse::class), function($mock) use ($mGoogle_service_GmailMessage) {
                        $mock->method('getMessages')->willReturn([
                            $mGoogle_service_GmailMessage
                        ]);
                    })
                );

                $mock->method('get')->willReturn($mGoogle_service_GmailMessage);
            });

        $mail = new \App\Services\Google\MailRepository($mGoogle_Service_Gmail);
        $this->assertAttributeInstanceOf(\Google_Service_Gmail::class, 'service', $mail);

        $messages = $mail->find('query:string');
        $this->assertInstanceOf(\Illuminate\Support\Collection::class, $messages);

        $message = $messages->first();
        $this->assertInstanceOf(\App\Services\Google\MailMessage::class, $message);
        $this->assertEquals('123456789', $message->getId());
        $this->assertEquals('Body for message 123456789', $message->getBody());
    }

}