April 2022
Beginner to intermediate
464 pages
6h 44m
Japanese
Content preview from 実用 Go言語 ―システム開発の現場で知っておきたいアドバイス
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13.8 構造体の比較にgo-cmpを使う
Goのテストにおいて、複雑な構造体の値を比較したいことがよくあります。ロジックの結果はなんらかの値として作用することが多いので、型の値を比較したいと思うのは自然なことです。値が等価かどうかの判定には、go-cmp 1というライブラリが便利です。
- 1
https://github.com/google/go-cmp 2021/12時点の最新である
v0.5.6で確認しています。
13.8.1 go-cmpを使う理由
構造体をstretchr/testifyを使って比較すると、reflect.DeepEqual()よりも手軽にわかりやすいエラーが表示できることは紹介しました。より高度な検証を行いたい場合、あるいはGoの標準のテストの書き方に合わせたいのであれば、go-cmpをおすすめします。
13.8.1.1 テストを標準的な形式で書きやすい
Goはテストのフレームワークを提供していません。テストは testing パッケージを使って実装します。どのようなフレームワークを使うかはプロジェクトメンバーの構成や状況によって変わるので、一概に何が良いと決めることはできません。Goはテストの書き方の標準的な書式を用意しており、Goにあまりなじみのない新規参画者やテストのフレームワークになじみのない開発者も、ベテランであっても同じようにテストコードを読めることを目指しています。go-cmp は reflect.DeeqEqual() の代わりに使用できます。
リスト13-6:
go-cmp を使ったスライスを含む構造体の比較 // go-cmp の Diff を使って値を比較
if diff := cmp.Diff(tomBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.