Package assert

import "bitbucket.org/rj/assert"

Overview
Index
Examples

Overview

Package assert provide a single function to emulate C-style asserts.

The goal of this package is to provide a call that will document and enforce preconditions, postconditions, and invariants in code. Failures should only result from program bugs. This package should not be used to replace proper error handling.

Assertions

Each assertion documents that a predicate is true when the the assertion is executed. Depending on the build, that predicate might also be enforced (i.e. by terminating the program, or, more gently, by panicing). There are three types of assertion: (1) preconditions, which document conditions (specified as predicates) for calling a function, (2) postconditions, which document conditions at the end of a function, and (3) invariant, which specify conditions over a particular scope or for a type.

If the predicate for an assertion is false, this conditions indicates a bug in the code (as opposed to a transient or run-time error). When enforced, assertions are a debugging tool.

Reference: https://golang.org/doc/faq#assertions, https://golang.org/ref/spec#Run_time_panics

Index

func Assert(predicate bool, message string)
type Error
func (e Error) Error() string
func (e Error) RuntimeError()

Examples

(Expand All)

Assert
Assert (Fail)
Assert (Sqrt)

Package files

assert.go

func Assert

func Assert(predicate bool, message string)

Assert will panic if the value of predicate is false.

Example

Code:

assert.Assert(true, "trivially true precondition")
fmt.Println("OK")

Output:

OK

Example (Fail)

Code:

defer func() {
    if r := recover(); r != nil {
        fmt.Println(r)
    }
}()

assert.Assert(false, "trivially false precondition")
fmt.Println("OK")

Output:

assertion error: trivially false precondition

Example (Sqrt)

Code:

// The square root function in package math returns NaN if the value is
// negative.  If instead we wanted a precondition that the value was
// non-negative, we could do the following (this is not a recommendation
// to change the contract for math.Sqrt).
sqrt := func(v float64) float64 {
    assert.Assert(v >= 0, "square root undefined for v<0")
    return math.Sqrt(v)
}

fmt.Printf("Sqrt of 1 is %0.1f\n", sqrt(1.0))

Output:

Sqrt of 1 is 1.0

type Error

Error contains error information from a failed call to Assert.

type Error string

func (Error) Error

func (e Error) Error() string

Error returns a string describing the error.

func (Error) RuntimeError

func (e Error) RuntimeError()

RuntimeError is a no-op function but serves to distinguish types that are run time errors from ordinary errors: a type is a run time error if it has a RuntimeError method.

See: https://godoc.org/runtime#Error

bitbucket.org/rj/assert

Package assert

Install

Getting Started

Contribute

License