fakefs

Documentation

Overview

Package fakefs contains fake implementations of interfaces from package io/fs from the standard library.

It is recommended to fill all methods that shouldn't be called with:

panic(testutil.UnexpectedCall(arg1, arg2))

See the package example.

Example

package main

import (
	"fmt"
	"io"
	"io/fs"

	"github.com/AdguardTeam/golibs/errors"
	"github.com/AdguardTeam/golibs/testutil"
	"github.com/AdguardTeam/golibs/testutil/fakeio/fakefs"
)

func main() {
	const testMsg = "test message"

	isClosed := false
	fakeFile := &fakefs.File{
		// Use OnClose to record the closure of the file.
		OnClose: func() (err error) {
			isClosed = true

			return nil
		},

		// Use OnRead to return the fake data.
		OnRead: func(b []byte) (n int, err error) {
			copy(b, testMsg)

			return len(testMsg), io.EOF
		},

		// Use OnStat with a panic to signal that Stat is expected to not be
		// called.
		OnStat: func() (fi fs.FileInfo, err error) { panic(testutil.UnexpectedCall()) },
	}

	fakeFS := &fakefs.FS{
		OnOpen: func(_ string) (f fs.File, err error) {
			return fakeFile, nil
		},
	}

	// The function that is expected to call Read and Close.
	testedFunction := func(fsys fs.FS) (b []byte, err error) {
		f, err := fsys.Open("my_file.txt")
		if err != nil {
			return nil, fmt.Errorf("opening: %w", err)
		}
		defer func() { err = errors.WithDeferred(err, f.Close()) }()

		b = make([]byte, len(testMsg)*2)
		n, err := f.Read(b)
		if err != nil && !errors.Is(err, io.EOF) {
			return nil, fmt.Errorf("reading: %w", err)
		}

		return b[:n], nil
	}

	// A simulation of a successful test.
	gotData, gotErr := testedFunction(fakeFS)
	fmt.Printf("read: %v %q\n", gotErr, gotData)
	fmt.Printf("closed: %t\n", isClosed)

}

Output:
read: <nil> "test message"
closed: true

Index

• type FS
  • func (fsys *FS) Open(name string) (f fs.File, err error)
• type File
  • func (f *File) Close() (err error)
  • func (f *File) Read(b []byte) (n int, err error)
  • func (f *File) Stat() (fi fs.FileInfo, err error)
• type GlobFS
  • func (fsys *GlobFS) Glob(pattern string) (paths []string, err error)
  • func (fsys *GlobFS) Open(name string) (f fs.File, err error)
• type StatFS
  • func (fsys *StatFS) Open(name string) (f fs.File, err error)
  • func (fsys *StatFS) Stat(name string) (fi fs.FileInfo, err error)

Examples

• Package

Types

type FS

type FS struct {
	OnOpen func(name string) (fs.File, error)
}

FS is the fs.FS for tests.

func (*FS) Open

func (fsys *FS) Open(name string) (f fs.File, err error)

Open implements the fs.FS interface for *FS.

type File

type File struct {
	OnClose func() error
	OnRead  func(b []byte) (n int, err error)
	OnStat  func() (fi fs.FileInfo, err error)
}

File is the fs.File for tests.

func (*File) Close

func (f *File) Close() (err error)

Close implements the fs.File interface for *File.

func (*File) Read

func (f *File) Read(b []byte) (n int, err error)

Read implements the fs.File interface for *File.

func (*File) Stat

func (f *File) Stat() (fi fs.FileInfo, err error)

Stat implements the fs.File interface for *File.

type GlobFS

type GlobFS struct {
	OnOpen func(name string) (f fs.File, err error)
	OnGlob func(pattern string) (paths []string, err error)
}

GlobFS is the fs.GlobFS for tests.

func (*GlobFS) Glob

func (fsys *GlobFS) Glob(pattern string) (paths []string, err error)

Glob implements the fs.GlobFS interface for *GlobFS.

func (*GlobFS) Open

func (fsys *GlobFS) Open(name string) (f fs.File, err error)

Open implements the fs.GlobFS interface for *GlobFS.

type StatFS

type StatFS struct {
	OnOpen func(name string) (f fs.File, err error)
	OnStat func(name string) (fi fs.FileInfo, err error)
}

StatFS is the fs.StatFS for tests.

func (*StatFS) Open

func (fsys *StatFS) Open(name string) (f fs.File, err error)

Open implements the fs.StatFS interface for *StatFS.

func (*StatFS) Stat

func (fsys *StatFS) Stat(name string) (fi fs.FileInfo, err error)

Stat implements the fs.StatFS interface for *StatFS.