gobycontract

Go By Contract

This is a simple implementation of production-safe Design by Contract in Go, using pre-conditions and post-conditions.

Whilst this implementation allows for errors to "fail hard" in development and staging environments, it also can be configured in a report-only mode for production environments.

This is an example of the following pattern: A Pattern for Validating Design by Contract Assertions in Production (with Go and Sentry)

Environment Variables

• GOBYCONTRACT_DONTPANIC when set to "true" will stop panicking when the Require or `````Ensure```` checks fail
• SENTRY_DSN is required to be set for the Sentry reporting of contract violations to be enabled

Per the Sentry Raven-Go documentation, the SENTRY_RELEASE and SENTRY_ENVIRONMENT environment variables may also be set.

Example Implementation

• Require is used to determine if a precondition is met
• Ensure is used to determine if a postcondition is met

Example of a function using such methods:

func SecondsToSecondsAndMinutes(seconds int) (minutes int, remainingSeconds int) {
	gobycontract.Require(seconds >= 0, "Input seconds must be positive")

	minutes = seconds/60
	remainingSeconds = seconds % 60

	gobycontract.Ensure(minutes >= 0, "Output minutes must be positive")
	gobycontract.Ensure(remainingSeconds >= 0, "Output remaining seconds must be positive")
	gobycontract.Ensure(remainingSeconds < 60, "There can be no more than 59 remaining seconds")

	return
}