existingProviders example

        $provider = $this->createTaxProviders([
            [
                'identifier' => 'test',
                'name' => 'lol',
                'processUrl' => 'https://example.com',
                'priority' => '1',
            ],
        ]);

        $manifest = $this->createManifest($provider);
        $existing = $this->existingProviders();

        $repo = $this->createMock(EntityRepository::class);
        $repo
            ->expects(static::once())
            ->method('search')
            ->willReturn($existing);
        $repo
            ->expects(static::once())
            ->method('upsert')
            ->with(
                [[