Dependency Injection Principles, Practices, and Patterns : https://www.amazon.co.uk/Dependency-Injection-NET-Second-Seemann/dp/161729473X
Clean Code: A Handbook of Agile Software Craftsmanship : https://www.amazon.co.uk/Clean-Code-Handbook-Software-Craftsmanship/dp/0132350882/
Test Driven Development: By Example : https://www.amazon.co.uk/Test-Driven-Development-Addison-Wesley-Signature/dp/0321146530/
Working Effectively with Legacy Code : https://www.amazon.co.uk/Working-Effectively-Legacy-Michael-Feathers/dp/0131177052
Refactoring: Improving the Design of Existing Code : https://www.amazon.co.uk/Refactoring-Improving-Existing-Addison-Wesley-Technology/dp/0134757599/
The Art of Unit Testing: with examples in C# : https://www.amazon.co.uk/Art-Unit-Testing-examples/dp/1617290890
The Clean Coder: A Code of Conduct for Professional Programmers : https://www.amazon.co.uk/Clean-Coder-Conduct-Professional-Programmers/dp/0137081073
Test-Driven iOS Development with Swift 4 : https://www.amazon.co.uk/Test-Driven-iOS-Development-Swift-maintainable/dp/1788475704/
Test-Driven iOS Development : https://www.amazon.co.uk/Test-Driven-iOS-Development-Developers-Library/dp/0321774183