mirror of
https://github.com/restic/restic.git
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188 lines
6.7 KiB
Go
188 lines
6.7 KiB
Go
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// Copyright 2016 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package testing provides support functions for testing iterators conforming
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// to the standard pattern.
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// See package google.golang.org/api/iterator and
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// https://github.com/GoogleCloudPlatform/gcloud-golang/wiki/Iterator-Guidelines.
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package testing
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import (
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"fmt"
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"reflect"
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"google.golang.org/api/iterator"
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)
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// TestIterator tests the Next method of a standard iterator. It assumes that
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// the underlying sequence to be iterated over already exists.
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//
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// The want argument should be a slice that contains the elements of this
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// sequence. It may be an empty slice, but it must not be the nil interface
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// value. The elements must be comparable with reflect.DeepEqual.
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//
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// The create function should create and return a new iterator.
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// It will typically look like
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// func() interface{} { return client.Items(ctx) }
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//
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// The next function takes the return value of create and should return the
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// result of calling Next on the iterator. It can usually be defined as
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// func(it interface{}) (interface{}, error) { return it.(*ItemIterator).Next() }
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//
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// TestIterator checks that the iterator returns all the elements of want
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// in order, followed by (zero, done). It also confirms that subsequent calls
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// to next also return (zero, done).
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//
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// If the iterator implements the method
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// PageInfo() *iterator.PageInfo
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// then exact pagination with iterator.Pager is also tested. Pagination testing
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// will be more informative if the want slice contains at least three elements.
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//
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// On success, TestIterator returns ("", true). On failure, it returns a
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// suitable error message and false.
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func TestIterator(want interface{}, create func() interface{}, next func(interface{}) (interface{}, error)) (string, bool) {
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vWant := reflect.ValueOf(want)
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if vWant.Kind() != reflect.Slice {
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return "'want' must be a slice", false
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}
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it := create()
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msg, ok := testNext(vWant, it, next)
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if !ok {
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return msg, ok
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}
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if _, ok := it.(iterator.Pageable); !ok || vWant.Len() == 0 {
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return "", true
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}
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return testPaging(vWant, create, next)
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}
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// Check that the iterator returns vWant, the desired sequence.
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func testNext(vWant reflect.Value, it interface{}, next func(interface{}) (interface{}, error)) (string, bool) {
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for i := 0; i < vWant.Len(); i++ {
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got, err := next(it)
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if err != nil {
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return fmt.Sprintf("#%d: got %v, expected an item", i, err), false
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}
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w := vWant.Index(i).Interface()
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if !reflect.DeepEqual(got, w) {
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return fmt.Sprintf("#%d: got %+v, want %+v", i, got, w), false
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}
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}
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// We now should see (<zero value of item type>, done), no matter how many
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// additional calls we make.
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zero := reflect.Zero(vWant.Type().Elem()).Interface()
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for i := 0; i < 3; i++ {
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got, err := next(it)
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if err != iterator.Done {
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return fmt.Sprintf("at end: got error %v, want iterator.Done", err), false
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}
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// Since err == iterator.Done, got should be zero.
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if got != zero {
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return fmt.Sprintf("got %+v with done, want zero %T", got, zero), false
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}
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}
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return "", true
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}
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// Test the iterator's behavior when used with iterator.Pager.
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func testPaging(vWant reflect.Value, create func() interface{}, next func(interface{}) (interface{}, error)) (string, bool) {
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// Test page sizes that are smaller, equal to, and greater than the length
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// of the expected sequence.
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for _, pageSize := range []int{1, 2, vWant.Len(), vWant.Len() + 10} {
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wantPages := wantedPages(vWant, pageSize)
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// Test the Pager in two ways.
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// First, by creating a single Pager and calling NextPage in a loop,
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// ignoring the page token except for detecting the end of the
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// iteration.
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it := create().(iterator.Pageable)
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pager := iterator.NewPager(it, pageSize, "")
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msg, ok := testPager(fmt.Sprintf("ignore page token, pageSize %d", pageSize),
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vWant.Type(), wantPages,
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func(_ string, pagep interface{}) (string, error) {
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return pager.NextPage(pagep)
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})
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if !ok {
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return msg, false
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}
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// Second, by creating a new Pager for each page, passing in the page
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// token from the previous page, as would be done in a web handler.
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it = create().(iterator.Pageable)
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msg, ok = testPager(fmt.Sprintf("use page token, pageSize %d", pageSize),
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vWant.Type(), wantPages,
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func(pageToken string, pagep interface{}) (string, error) {
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return iterator.NewPager(it, pageSize, pageToken).NextPage(pagep)
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})
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if !ok {
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return msg, false
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}
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}
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return "", true
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}
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// Create the pages we expect to see.
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func wantedPages(vWant reflect.Value, pageSize int) []interface{} {
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var pages []interface{}
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for i, j := 0, pageSize; i < vWant.Len(); i, j = j, j+pageSize {
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if j > vWant.Len() {
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j = vWant.Len()
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}
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pages = append(pages, vWant.Slice(i, j).Interface())
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}
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return pages
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}
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func testPager(prefix string, sliceType reflect.Type, wantPages []interface{},
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nextPage func(pageToken string, pagep interface{}) (string, error)) (string, bool) {
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tok := ""
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var err error
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for i := 0; i < len(wantPages)+1; i++ {
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vpagep := reflect.New(sliceType)
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tok, err = nextPage(tok, vpagep.Interface())
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if err != nil {
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return fmt.Sprintf("%s, page #%d: got error %v", prefix, i, err), false
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}
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if i == len(wantPages) {
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// Allow one empty page at the end.
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if vpagep.Elem().Len() != 0 || tok != "" {
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return fmt.Sprintf("%s: did not get one empty page at end", prefix), false
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}
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break
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}
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if msg, ok := compareSlices(vpagep.Elem(), reflect.ValueOf(wantPages[i])); !ok {
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return fmt.Sprintf("%s, page #%d:\n%s", prefix, i, msg), false
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}
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if tok == "" {
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if i != len(wantPages)-1 {
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return fmt.Sprintf("%s, page #%d: got empty page token", prefix, i), false
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}
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break
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}
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}
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return "", true
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}
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// Compare two slices element-by-element. If they are equal, return ("", true).
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// Otherwise, return a description of the difference and false.
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func compareSlices(vgot, vwant reflect.Value) (string, bool) {
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if got, want := vgot.Len(), vwant.Len(); got != want {
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return fmt.Sprintf("got %d items, want %d", got, want), false
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}
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for i := 0; i < vgot.Len(); i++ {
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if got, want := vgot.Index(i).Interface(), vwant.Index(i).Interface(); !reflect.DeepEqual(got, want) {
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return fmt.Sprintf("got[%d] = %+v\nwant = %+v", i, got, want), false
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}
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}
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return "", true
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}
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