must

README

Must Package

Package must provide a set of helper functions which panic on error. Functions are designed to simplify error handling in test code by panicking on errors, reduce boilerplate, and error checking in test cases.

Documentation

Overview

Package must provide a set of helper functions which panic on error.

Functions are designed to simplify error handling in test code by panicking on errors, reduce boilerplate, and error checking in test cases.

Index

• func First[T any](s []T, err error) T
• func Nil(err error)
• func Single[T any](s []T, err error) T
• func Value[T any](val T, err error) T
• func Values[T, TT any](val0 T, val1 TT, err error) (T, TT)

Examples

• First
• Single

Functions

func First

func First[T any](s []T, err error) T

First returns the first element in the slice or T's zero value if the slice is empty. It panics with value of err if err is not nil.

Example

nolint:unparam

package main

import (
	"fmt"

	"github.com/ctx42/testing/pkg/must"
)

func main() {
	type Row struct{ Name string }

	// Query to database returning rows.
	query := func() ([]Row, error) {
		return []Row{{"a"}, {"b"}}, nil
	}

	have := must.First(query())

	fmt.Println(have)
}

Output:

{a}

func Nil

func Nil(err error)

Nil is a helper function which panics if an error is not nil.

func Single

func Single[T any](s []T, err error) T

Single returns the first element in the slice or T's zero value if the slice is empty. It panics with value of err if err is not nil or with value of errExpSingle if slices has more than one element.

Example

nolint:unparam

package main

import (
	"fmt"

	"github.com/ctx42/testing/pkg/must"
)

func main() {
	type Row struct{ Name string }

	// Query to database returning rows.
	query := func() ([]Row, error) {
		return []Row{{"a"}}, nil
	}

	// Will panic if database returned more than one error.
	have := must.Single(query())

	fmt.Println(have)
}

Output:

{a}

func Value

func Value[T any](val T, err error) T

Value is a helper for functions returning (T, error) panicking if returned error is not nil. Example:

fil := Value(os.Open("file.txt"))

func Values

func Values[T, TT any](val0 T, val1 TT, err error) (T, TT)

Values is a helper for functions returning (T1, T2, error) panicking if returned error is not nil. Example:

t1, t2 := Values(DoSomething())