Rspec tốt hơn

Thứ Bảy, 19/12/2020

Tram Ho

Developer không chỉ code mà cần phải viết test đi kèm theo với Code

Trong ngôn ngữ Ruby, RSpec là một trong những testing framework được sử dụng phổ biến nhất. Việc viết test khi coding giúp ích rất nhiều cho developer trong việc đảm bảo chất lượng của các đoạn code được test, giúp điều tra bug xảy ra dễ dàng hơn.

Bài viết này chúng ta cùng tìm hiểu một số tip nên được sử dụng khi viết rspec, giúp các đoạn code testing trở nên hiệu quả và cũng dễ dàng trong việc đọc, maintain

Structure code to right place

Tất cả các test case đều bao gồm 3 block:

Setup: Phần code chuẩn bị trước khi chạy test, như khởi tạo các biến , action(let, let!), chạy các function trước khi test(before)
Assert: Phần code chứa các test case được khai báo(it)
Teardown: Phần code sau khi đã chạy qua các test case(after), thường có nhiệm vụ dọn dẹp, khôi phục các trạng thái được setup ban đầu

Khi viết test ta nên cấu trúc, phân chia code theo đúng các block ở trên:

<span class="token comment"># BAD</span>

describe <span class="token string">"#upload"</span> <span class="token keyword">do</span>
    it <span class="token string">"should upload success"</span> <span class="token keyword">do</span>
         user<span class="token punctuation">.</span>uploader<span class="token punctuation">.</span>open
         expect <span class="token punctuation">{</span> user<span class="token punctuation">.</span>upload <span class="token punctuation">}</span><span class="token punctuation">.</span>to change <span class="token punctuation">{</span> user<span class="token punctuation">.</span>images<span class="token punctuation">.</span>size <span class="token punctuation">}</span><span class="token punctuation">.</span>by<span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span>
         user<span class="token punctuation">.</span>uploader<span class="token punctuation">.</span>close
    <span class="token keyword">end</span>
<span class="token keyword">end</span>

<span class="token comment"># GOOD</span>

describe <span class="token string">"#upload"</span> <span class="token keyword">do</span>
    <span class="token comment"># Setup</span>
    let<span class="token punctuation">(</span><span class="token symbol">:user</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> create <span class="token symbol">:user</span><span class="token punctuation">,</span> <span class="token symbol">:with_images</span> <span class="token punctuation">}</span>
    let<span class="token punctuation">(</span><span class="token symbol">:action</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> user<span class="token punctuation">.</span>upload <span class="token punctuation">}</span>
  
    before <span class="token punctuation">{</span> user<span class="token punctuation">.</span>uploader<span class="token punctuation">.</span>open <span class="token punctuation">}</span>
    
    <span class="token comment"># Teardown</span>
    after <span class="token punctuation">{</span> user<span class="token punctuation">.</span>uploader<span class="token punctuation">.</span>close <span class="token punctuation">}</span>
   
   <span class="token comment"># Assert</span>
    it <span class="token string">"should upload success"</span> <span class="token keyword">do</span>
         expect <span class="token punctuation">{</span> action <span class="token punctuation">}</span><span class="token punctuation">.</span>to change <span class="token punctuation">{</span> user<span class="token punctuation">.</span>images<span class="token punctuation">.</span>size <span class="token punctuation">}</span><span class="token punctuation">.</span>by<span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span>
    <span class="token keyword">end</span>
<span class="token keyword">end</span>

# BAD

describe "#upload" do

it "should upload success" do

user.uploader.open

expect { user.upload }.to change { user.images.size }.by(1)

user.uploader.close

end

# GOOD

describe "#upload" do

# Setup

let(:user) { create :user, :with_images }

let(:action) { user.upload }

before { user.uploader.open }

# Teardown

after { user.uploader.close }

# Assert

it "should upload success" do

expect { action }.to change { user.images.size }.by(1)

end

Use instance_double instead of double

Trong quá trình viết test, có thể ta muốn mock instances của một Class nào đó, khi đó sử dụng instance_double sẽ an toàn hơn sử dụng double:

<span class="token keyword">class</span> <span class="token class-name">User</span>
    <span class="token keyword">def</span> <span class="token method-definition"><span class="token function">show_info</span></span>
       <span class="token comment">#  ...</span>
    <span class="token keyword">end</span>
<span class="token keyword">end</span>

<span class="token comment"># use double</span>
sherlock <span class="token operator">=</span> double<span class="token punctuation">(</span><span class="token string">"User"</span><span class="token punctuation">)</span>
allow<span class="token punctuation">(</span>sherlock<span class="token punctuation">)</span><span class="token punctuation">.</span>to receive<span class="token punctuation">(</span><span class="token symbol">:show_info</span><span class="token punctuation">)</span> <span class="token comment"># =&gt; OK</span>
allow<span class="token punctuation">(</span>sherlock<span class="token punctuation">)</span><span class="token punctuation">.</span>to receive<span class="token punctuation">(</span><span class="token symbol">:show_info</span><span class="token punctuation">)</span><span class="token punctuation">.</span>with<span class="token punctuation">(</span><span class="token symbol">:name</span><span class="token punctuation">)</span> <span class="token comment"># =&gt; Fail, nhưng không raise exception</span>
allow<span class="token punctuation">(</span>sherlock<span class="token punctuation">)</span><span class="token punctuation">.</span>to receive<span class="token punctuation">(</span><span class="token symbol">:some_method</span><span class="token punctuation">)</span> <span class="token comment"># Fail, cũng không raise exception</span>

<span class="token comment"># use instance_double</span>
sherlock <span class="token operator">=</span> instance_double<span class="token punctuation">(</span><span class="token string">"User"</span><span class="token punctuation">)</span>
allow<span class="token punctuation">(</span>sherlock<span class="token punctuation">)</span><span class="token punctuation">.</span>to receive<span class="token punctuation">(</span><span class="token symbol">:show_info</span><span class="token punctuation">)</span> <span class="token comment"># =&gt; OK</span>
allow<span class="token punctuation">(</span>sherlock<span class="token punctuation">)</span><span class="token punctuation">.</span>to receive<span class="token punctuation">(</span><span class="token symbol">:show_info</span><span class="token punctuation">)</span><span class="token punctuation">.</span>with<span class="token punctuation">(</span><span class="token symbol">:name</span><span class="token punctuation">)</span> <span class="token comment"># =&gt; Fail, raise wrong number of argument</span>
allow<span class="token punctuation">(</span>sherlock<span class="token punctuation">)</span><span class="token punctuation">.</span>to receive<span class="token punctuation">(</span><span class="token symbol">:some_method</span><span class="token punctuation">)</span> <span class="token comment"># Fail, raise method not implement</span>

class User

def show_info

# ...

end

# use double

sherlock = double("User")

allow(sherlock).to receive(:show_info).with(:name) # => Fail, nhưng không raise exception

# use instance_double

sherlock = instance_double("User")

DESCRIBE for testing target, CONTEXT for scenarios

Dùng Describe để chỉ định đối tượng cần test, Context để mô tả các test case có thể xảy ra, giúp việc code trở nên dễ track hơn, hơn nữa, các context cũng được phân chia, phân biệt với các context khác

describe <span class="token string">"#authenticate"</span> <span class="token keyword">do</span>
    let<span class="token operator">!</span><span class="token punctuation">(</span><span class="token symbol">:user</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> create <span class="token symbol">:user</span><span class="token punctuation">,</span> email<span class="token punctuation">:</span> <span class="token string">"<a class="__cf_email__" href="/cdn-cgi/l/email-protection">[email protected]</a>"</span><span class="token punctuation">,</span> password<span class="token punctuation">:</span> <span class="token string">"123456"</span> <span class="token punctuation">}</span>
  
    context <span class="token string">"when email and password not match"</span> <span class="token keyword">do</span>
        let<span class="token punctuation">(</span><span class="token symbol">:param</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token punctuation">{</span> email<span class="token punctuation">:</span> <span class="token string">"<a class="__cf_email__" href="/cdn-cgi/l/email-protection">[email protected]</a>"</span><span class="token punctuation">,</span> password<span class="token punctuation">:</span> <span class="token string">"xxxxxx"</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span>
        
        it <span class="token string">"should return failure"</span> <span class="token keyword">do</span>
            <span class="token comment"># ...</span>
        <span class="token keyword">end</span>
    <span class="token keyword">end</span>
    
    context <span class="token string">"when email and password match"</span> <span class="token keyword">do</span>
        let<span class="token punctuation">(</span><span class="token symbol">:param</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token punctuation">{</span> email<span class="token punctuation">:</span> <span class="token string">"<a class="__cf_email__" href="/cdn-cgi/l/email-protection">[email protected]</a>"</span><span class="token punctuation">,</span> password<span class="token punctuation">:</span> <span class="token string">"123456"</span> <span class="token punctuation">}</span> <span class="token punctuation">}</span>
        
        it <span class="token string">"should return success"</span> <span class="token keyword">do</span>
            <span class="token comment"># ...</span>
        <span class="token keyword">end</span>
    <span class="token keyword">end</span>
<span class="token keyword">end</span>

describe "#authenticate" do

let!(:user) { create :user, email: "<a class="__cf_email__" href="/cdn-cgi/l/email-protection">[email protected]</a>", password: "123456" }

context "when email and password not match" do

let(:param) { { email: "<a class="__cf_email__" href="/cdn-cgi/l/email-protection">[email protected]</a>", password: "xxxxxx" } }

it "should return failure" do

# ...

end

context "when email and password match" do

let(:param) { { email: "<a class="__cf_email__" href="/cdn-cgi/l/email-protection">[email protected]</a>", password: "123456" } }

it "should return success" do

# ...

end

Understand how transactions work in RSpec

Transaction mặc định được tạo vào gắn mỗi một example trong Rspec, cho phép database rolled backed về trạng thái ban đầu, sử dụng cho những example sau đó.

Các record được tạo trong before(:context) hay before(:all) sẽ không bị rolled back:

context <span class="token string">"context 1"</span> <span class="token keyword">do</span>
  before<span class="token punctuation">(</span><span class="token symbol">:context</span><span class="token punctuation">)</span> <span class="token keyword">do</span>
    create<span class="token punctuation">(</span><span class="token symbol">:user</span><span class="token punctuation">)</span> <span class="token comment"># WON"T BE ROLLED-BACK</span>
  <span class="token keyword">end</span>

  before <span class="token keyword">do</span>
    create<span class="token punctuation">(</span><span class="token symbol">:user</span><span class="token punctuation">)</span> <span class="token comment"># will be rolled-back</span>
  <span class="token keyword">end</span>

  <span class="token comment"># ...</span>
<span class="token keyword">end</span>

context <span class="token string">"context 2"</span> <span class="token keyword">do</span>
  before<span class="token punctuation">(</span><span class="token symbol">:context</span><span class="token punctuation">)</span> <span class="token keyword">do</span>
    create<span class="token punctuation">(</span><span class="token symbol">:user</span><span class="token punctuation">)</span> <span class="token comment"># WON"T BE ROLLED-BACK</span>
  <span class="token keyword">end</span>

  <span class="token comment"># ...</span>
<span class="token keyword">end</span>

<span class="token comment"># BY NOW, THERE ARE 2 USER RECORDS COMMITED TO DATABASE</span>

context "context 1" do

before(:context) do

create(:user) # WON"T BE ROLLED-BACK

end

before do

create(:user) # will be rolled-back

end

# ...

end

context "context 2" do

before(:context) do

create(:user) # WON"T BE ROLLED-BACK

end

# ...

end

# BY NOW, THERE ARE 2 USER RECORDS COMMITED TO DATABASE

Use bulk method if possible

<span class="token comment"># BAD</span>

it <span class="token string">"should update user success"</span> <span class="token keyword">do</span>
    expect<span class="token punctuation">(</span>user<span class="token punctuation">.</span>name<span class="token punctuation">)</span><span class="token punctuation">.</span>eq <span class="token string">"Sherlock"</span>
    expect<span class="token punctuation">(</span>user<span class="token punctuation">.</span>email<span class="token punctuation">)</span><span class="token punctuation">.</span>eq <span class="token string">"<a class="__cf_email__" href="/cdn-cgi/l/email-protection">[email protected]</a>"</span>
    expect<span class="token punctuation">(</span>user<span class="token punctuation">.</span>sex<span class="token punctuation">)</span><span class="token punctuation">.</span>eq <span class="token string">"Male"</span>
    expect<span class="token punctuation">(</span>user<span class="token punctuation">.</span>address<span class="token punctuation">)</span><span class="token punctuation">.</span>eq <span class="token string">"221 Baker street"</span>
    expect<span class="token punctuation">(</span>user<span class="token punctuation">.</span>phone<span class="token punctuation">)</span><span class="token punctuation">.</span>eq <span class="token string">"12345678"</span>
<span class="token keyword">end</span>

<span class="token comment"># GOOD</span>

it <span class="token string">"should update user success"</span> <span class="token keyword">do</span>
    expect<span class="token punctuation">(</span>user<span class="token punctuation">)</span><span class="token punctuation">.</span>to have_attributes<span class="token punctuation">(</span>
        name<span class="token punctuation">:</span> <span class="token string">"Sherlock"</span><span class="token punctuation">,</span>
        email<span class="token punctuation">:</span> <span class="token string">"<a class="__cf_email__" href="/cdn-cgi/l/email-protection">[email protected]</a>"</span><span class="token punctuation">,</span>
        sex<span class="token punctuation">:</span> <span class="token string">"Male"</span><span class="token punctuation">,</span>
        address<span class="token punctuation">:</span> <span class="token string">"221 Baker street"</span><span class="token punctuation">,</span>
        phone<span class="token punctuation">:</span> <span class="token string">"12345678"</span>
    <span class="token punctuation">)</span>
<span class="token keyword">end</span>

# BAD

it "should update user success" do

expect(user.name).eq "Sherlock"

expect(user.email).eq "<a class="__cf_email__" href="/cdn-cgi/l/email-protection">[email protected]</a>"

expect(user.sex).eq "Male"

expect(user.address).eq "221 Baker street"

expect(user.phone).eq "12345678"

end

# GOOD

it "should update user success" do

expect(user).to have_attributes(

name: "Sherlock",

email: "<a class="__cf_email__" href="/cdn-cgi/l/email-protection">[email protected]</a>",

sex: "Male",

address: "221 Baker street",

phone: "12345678"

)

end

VIết như trên tránh việc lặp những đoạn code giống nhau (DRY), cũng như chỉ ra tất cả các assertion đều dùng cho một object

Use configs for patterned test case

Cũng là một các viết DRY, code trông gọn hơn và giúp cho người đọc dễ follow hơn:

<span class="token comment"># BAD</span>
<span class="token comment">#</span>
describe <span class="token string">".extract_extension"</span> <span class="token keyword">do</span>
  subject <span class="token punctuation">{</span> described_class<span class="token punctuation">.</span>extract_extension<span class="token punctuation">(</span>filename<span class="token punctuation">)</span> <span class="token punctuation">}</span>
  
  context <span class="token string">"when the filename is empty"</span> <span class="token keyword">do</span>
    let<span class="token punctuation">(</span><span class="token symbol">:filename</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token string">""</span> <span class="token punctuation">}</span>
    it <span class="token punctuation">{</span> is_expected<span class="token punctuation">.</span>to eq <span class="token string">""</span> <span class="token punctuation">}</span>
  <span class="token keyword">end</span>

  context <span class="token string">"when the filename is video123.mp4"</span> <span class="token keyword">do</span>
    let<span class="token punctuation">(</span><span class="token symbol">:filename</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token string">"video123.mp4"</span> <span class="token punctuation">}</span>
    it <span class="token punctuation">{</span> is_expected<span class="token punctuation">.</span>to eq <span class="token string">"mp4"</span> <span class="token punctuation">}</span>
  <span class="token keyword">end</span>

  context <span class="token string">"when the filename is video.edited.mp4"</span> <span class="token keyword">do</span>
    let<span class="token punctuation">(</span><span class="token symbol">:filename</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token string">"video.edited.mp4"</span> <span class="token punctuation">}</span>
    it <span class="token punctuation">{</span> is_expected<span class="token punctuation">.</span>to eq <span class="token string">"mp4"</span> <span class="token punctuation">}</span>
  <span class="token keyword">end</span>

  context <span class="token string">"when the filename is video-edited"</span> <span class="token keyword">do</span>
    let<span class="token punctuation">(</span><span class="token symbol">:filename</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token string">"video-edited"</span> <span class="token punctuation">}</span>
    it <span class="token punctuation">{</span> is_expected<span class="token punctuation">.</span>to eq <span class="token string">""</span> <span class="token punctuation">}</span>
  <span class="token keyword">end</span>

  context <span class="token string">"when the filename is .mp4"</span> <span class="token keyword">do</span>
    let<span class="token punctuation">(</span><span class="token symbol">:filename</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token string">".mp4"</span> <span class="token punctuation">}</span>
    it <span class="token punctuation">{</span> is_expected<span class="token punctuation">.</span>to eq <span class="token string">""</span> <span class="token punctuation">}</span>
  <span class="token keyword">end</span>
<span class="token keyword">end</span>


<span class="token comment"># GOOD</span>
<span class="token comment">#</span>
describe <span class="token string">".extract_extension"</span> <span class="token keyword">do</span>
  subject <span class="token punctuation">{</span> described_class<span class="token punctuation">.</span>extract_extension<span class="token punctuation">(</span>filename<span class="token punctuation">)</span> <span class="token punctuation">}</span>

  test_cases <span class="token operator">=</span> <span class="token punctuation">[</span>
    <span class="token string">""</span> <span class="token operator">=</span><span class="token operator">&gt;</span> <span class="token string">""</span><span class="token punctuation">,</span>
    <span class="token string">"video123.mp4"</span> <span class="token operator">=</span><span class="token operator">&gt;</span> <span class="token string">"mp4"</span>
    <span class="token string">"video.edited.mp4"</span> <span class="token operator">=</span><span class="token operator">&gt;</span> <span class="token string">"mp4"</span>
    <span class="token string">"video-edited"</span> <span class="token operator">=</span><span class="token operator">&gt;</span> <span class="token string">""</span>
    <span class="token string">".mp4"</span> <span class="token operator">=</span><span class="token operator">&gt;</span> <span class="token string">""</span>
  <span class="token punctuation">]</span>

  test_cases<span class="token punctuation">.</span><span class="token keyword">each</span> <span class="token keyword">do</span> <span class="token operator">|</span>test_filename<span class="token punctuation">,</span> extension<span class="token operator">|</span>
    context <span class="token string">"when filename = <span class="token interpolation"><span class="token delimiter tag">#{</span>test_filename<span class="token delimiter tag">}</span></span>"</span> <span class="token keyword">do</span>
      let<span class="token punctuation">(</span><span class="token symbol">:filename</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> test_filename <span class="token punctuation">}</span>
      it <span class="token punctuation">{</span> is_expected<span class="token punctuation">.</span>to eq extension <span class="token punctuation">}</span>
    <span class="token keyword">end</span>
  <span class="token keyword">end</span>
<span class="token keyword">end</span>

# BAD

#

describe ".extract_extension" do

subject { described_class.extract_extension(filename) }

context "when the filename is empty" do

let(:filename) { "" }

it { is_expected.to eq "" }

end

context "when the filename is video123.mp4" do

it { is_expected.to eq "mp4" }

end

context "when the filename is video.edited.mp4" do

it { is_expected.to eq "mp4" }

end

context "when the filename is video-edited" do

it { is_expected.to eq "" }

end

context "when the filename is .mp4" do

it { is_expected.to eq "" }

end

# GOOD

#

describe ".extract_extension" do

test_cases = [

"" => "",

"video123.mp4" => "mp4"

"video.edited.mp4" => "mp4"

"video-edited" => ""

".mp4" => ""

]

test_cases.each do |test_filename, extension|

context "when filename = #{test_filename}" do

let(:filename) { test_filename }

it { is_expected.to eq extension }

end

Trên đây là một số tip mình tìm hiểu được trong quá trình viết Rspec, cảm ơn mọi người đã theo dõi

Chia sẻ bài viết ngay

Nguồn bài viết : Viblo

Rspec tốt hơn

Structure code to right place

Use instance_double instead of double

DESCRIBE for testing target, CONTEXT for scenarios

Understand how transactions work in RSpec

Use bulk method if possible

Use configs for patterned test case

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