How do you define object-oriented software contracts and behaviors?

It's important to determine if a provider will be idempotent in its execution. This can be important in a micro service architecture where a single event could be processed more than once by the provider.

Software behaviors can be expressed in different ways, such as pseudocode, natural language, diagrams or formal specifications. In the object-oriented approach, the importance is on documenting the structure and behavior of systems into small modules that combines both data and process.

Make sure your software contracts mirror the actual business requirements and allow for updates in the future. Be careful not to over engineer your solution using object oriented features like inheritance.

It's a strict defined API. I.e. a set of methods (or functions if it is not OOP), theirs parameters, and perhaps theirs behaviour, that a piece of software should fulfill in order to satisfy a contract

Contracts: Formal agreements on how to interact with an object. Behaviors: The actual actions and reactions of an object in a system.

Software behavior is how a program functions and responds to different inputs, event, and conditions, outlining its actions and responses.

Software behaviors encompass how a program responds to input, processes data, and produces output. These behaviors are typically defined by the code and logic written by developers during the software development process

In the case of API contracts, developers should think about versioning from the start. Software evolve and with it APIs can become complex. It’s beneficial to think about how the contract may evolve in version n compared to current version. That being said, avoid over-engineering and think from first principles while defining contracts.

Software behaviors are the actions and responses of a program when it is executed. Those behaviors are the result of the program's instructions & logic and determine how it interacts with users, hardware, and other software components. Some of the software behaviors could be Functional, User interaction, Interoperability, Security, Performance. Understanding & defining those behaviors is a crucial part of development process, as it helps in design, implement, test, and maintain software that meets user expectations & functional requirements while ensuring security, performance, and reliability.

UML sequence & state diagrams help a lot during feature planning and code review, they automatically became a part of documentation as well which helps to onboard new team members

One benefit of Contracts is that they are yet another form of code as documentation, and a good step towards "self-documenting code".

Contracts are useful when different developers are implementing the provider and consumer. By agreeing the contract up front, the development of the provider and consumer can be completed independently with a high degree of confidence that they will work well together on completion. This could be across module boundaries, between front and and backend (via API) or even between microservices. In any case, they allow the division of labour to achieve a goal.

This paragraph is trivial and has nothing to add. If we consider software contracts as simple data architecture we give a developer information on how to use API and which data need to be exchanged. Software behaviors are important because internal architecture is transparent for newly created components or box one saving design time - the view is based on effect which may be complicated in real products. Any kind of documentation has its receiver so if it has more details project maintains less vulnerabilities and it wastes less time to get basic project data

An example I’ve seen is with abstraction it helps not only to hide the implementation from the consumer of the class which could speed up the compilation, but also simply allows to mock the dependencies for the unit tests

By enforcing preconditions, contracts intercept invalid inputs, averting potential errors before execution. Postconditions confirm that components perform as intended, bolstering reliability. Contracts also foster interoperability. When components adhere to well-defined contracts, they seamlessly integrate into larger systems, encouraging code reuse. This not only streamlines development but also enhances collaboration among developers, as they share a common understanding of interactions. Maintenance is simplified when behaviors are well-documented within objects or components. Developers can confidently modify or extend code, knowing it won't disrupt other parts of the system.

In object-oriented design, software contracts are the guiding agreements that specify how objects should interact. They establish the rules for communication, outlining what's expected from each object. Contracts include preconditions (conditions objects must meet before an action), postconditions (results after an action), and invariants (conditions always true). Behaviors, on the other hand, describe how objects respond to messages or actions. They're the "how" in software design. Behaviors define the actual operations an object can perform. These well-defined behaviors make code more understandable, maintainable, and adaptable. They foster robust, error-free, and collaborative software development.

Class Diagram, Sequence Diagram and User-Interaction diagram are three different pillars of UML design which captures pretty much everything required to understand the design and subsequently implement the same. Class Diagram depicts the contracts and its implementations. Sequence diagram throw up the sequence of events which flow across different objects in the design. User-interaction diagram captures how user end up using this module. There are bunch of UML tools available in the market with most of the useful ones being paid. Go for one which provides reverse-engineering options since on agile development model, you could find engineers deriving UML from the code instead of the regular UML to code.

Test driven development(TDD) would mean once the contracts and behaviors are defined, we would subsequently work on writing compile time tests (google-test and likes of it) which would verify the implementation of those contracts and behaviors even before they are written. TDD typically means test-case is written and the failure is hit in absence of the code and then the code is written to make the test-case pass. Motivation to write a code should be coming from the failing test-case. It makes the code that much more purposeful.

There should be a more deeply described methodology and tools. I don't think readers would be satisfied by a few tools and analysis methods without context. Also, it's worth mentioning if we have any data architecture and we just checking if the truth is satisfied or if we are in... big trouble without any knowledge of how components are exchanging data. Behaviors are mostly verified via testing manual or automated.

I think this is the right time to start documentation for this particular object cluster which is worth outsourcing. In my opinion contract will be the best information for a beginner if the result is as expected and code works. If you do not want to put contract in document this would show the design and work flow was not as written on this descriptive contract. Metrics of time in contract will be a good information to evaluate the complexity of objects. And later expected and realised time quantities would be worth to be recorded. Product life cycle management is valid for software products as well and entire history is important from birth , usage , improvement and re-cyle periods.