context.SaveChanges(); statement duplicated

It's used in both method of the class BlogServiceTests but the method BusinessLogic.BlogService.Add(string url) also use context.SaveChanges();

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#### Document Details

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* ID: e4f7b56f-7f91-2f15-1fb6-4f481e97534f
* Version Independent ID: 6d9c65c6-f159-b234-48fd-f25da05f0f32
* Content: [Testing with SQLite - EF Core](https://docs.microsoft.com/en-us/ef/core/miscellaneous/testing/sqlite#feedback)
* Content Source: [entity-framework/core/miscellaneous/testing/sqlite.md](https://github.com/aspnet/EntityFramework.Docs/blob/master/entity-framework/core/miscellaneous/testing/sqlite.md)
* Product: **entity-framework**
* Technology: **entity-framework-core**
* GitHub Login: @rowanmiller
* Microsoft Alias: **avickers**