Creating Test for service with Contextual Binding

I created a TemplateServiceInterface that is being used by my EmailTemplateService and SmsTemplateService. They are both being used in different controller. the problem was when I was testing the EmailTemplateService, Im getting an error of Target [App\Contracts\TemplateServiceInterface] is not instantiable.

here's my test

class EmailTemplateServiceTest extends TestCase
{
    use RefreshDatabase;

    private $user = null;

    private $service = null;

    /**
     * test that the service can return available email templates
     */
    public function testServiceCanReturnAvailableEmailTemplates()
    {
        $this->prepare();

        $templates = $this->service->getAvailablePublicTemplates($this->user->user_code);
        $this->assertCount(0, $templates);
    }

    /**
     * Prepares the test environment with authentication
     */
    public function prepare($abilities = [])
    {
        $this->withoutExceptionHandling();

        $this->service = app()->make(TemplateServiceInterface::class);
        $this->assertInstanceOf(\App\Services\EmailTemplateService::class, $this->service);

        $this->user = User::factory()->create();

        Sanctum::actingAs(  $this->user, $abilities );
    }
}

on my AppServiceProvider.php I currently have this line.

        $this->app->when(EmailTemplateController::class)
            ->needs(TemplateServiceInterface::class)
            ->give(function($app) {
                return new EmailTemplateService();
            });

I haven't created the binding for the SmsTemplateService yet. I did try to change the binding to the test class but to no avail.

        $this->app->when(EmailTemplateServiceTest::class)
            ->needs(TemplateServiceInterface::class)
            ->give(function($app) {
                return new EmailTemplateService();
            });

Can anyone tell me how? thanks