Common approach of all that you are after for, can be the abstraction level of Coding conventions. Since they are set of guidelines for a programming languages that recommend programming style, practices and methods for each aspect of a piece program written. These conventions usually cover file organization,indentation, comments, declarations,statements, white space, naming conventions, programming practices,programming principles, programming rules of thumb, architectural best practices, etc.
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enable and encourage, other developers to provide implementations that are identical in functionality to mine.
you can use Interfaces (protocols). Even if they are used to define an abstract type that contains no data or code, they also define behaviors as method signatures.
Your examples are good. But in addition to
Provide a testing framework so they can validate their implementation
you can introduce the main ideas of the Test-driven development:
Establishing the goals of different stakeholders required for a vision to be implemented
Drawing out features which will achieve those goals using feature injection
The goal of developer TDD is to specify a detailed, executable design for your solution
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