XUnit数据共享与并行测试

引言

在单元或者集成测试的过程中，需要测试的用例非常多，如果测试是一条一条过，那么需要花费不少的时间。从 V2 开始，默认情况下 XUnit 自动配置并行（参考资料），大大提升了测试速度。本文将对 ASP.NET CORE WEBAPI 程序进行集成测试，并探讨 XUnit 的数据共享与测试并行的方法。

XUnit默认在一个类内的测试代码是串行执行的，而在不同类的测试代码是并行执行的。

集成测试

对于集成测试来说，我们有一些比较重的资源初始化，而我并不想他们在并行执行中重复初始化，因此需要将并行执行的资源共享。
我们现在的测试类是这样的：

1.     public class ProgramTests : IClassFixture<WebApplicationFactory<Program>>
2.     {
3. <ItemGroup>
4.      <InternalsVisibleTo Include="MyTestProject" />
5. </ItemGroup>   private readonly WebApplicationFactory<Program> _factory;
6. <ItemGroup>
7.      <InternalsVisibleTo Include="MyTestProject" />
8. </ItemGroup>   private readonly ITestOutputHelper testOutputHelper;
9. <ItemGroup>
10.      <InternalsVisibleTo Include="MyTestProject" />
11. </ItemGroup>   private readonly HttpClient _client;
12. <ItemGroup>
13.      <InternalsVisibleTo Include="MyTestProject" />
14. </ItemGroup>   public ProgramTests(WebApplicationFactory<Program> factory, ITestOutputHelper testOutputHelper)
15. <ItemGroup>
16.      <InternalsVisibleTo Include="MyTestProject" />
17. </ItemGroup>   {
18. <ItemGroup>
19.      <InternalsVisibleTo Include="MyTestProject" />
20. </ItemGroup><ItemGroup>
21.      <InternalsVisibleTo Include="MyTestProject" />
22. </ItemGroup>  _factory = factory;
23. <ItemGroup>
24.      <InternalsVisibleTo Include="MyTestProject" />
25. </ItemGroup><ItemGroup>
26.      <InternalsVisibleTo Include="MyTestProject" />
27. </ItemGroup>  this.testOutputHelper = testOutputHelper;
28. <ItemGroup>
29.      <InternalsVisibleTo Include="MyTestProject" />
30. </ItemGroup><ItemGroup>
31.      <InternalsVisibleTo Include="MyTestProject" />
32. </ItemGroup>  _client = _factory.WithWebHostBuilder(builder =>
33. <ItemGroup>
34.      <InternalsVisibleTo Include="MyTestProject" />
35. </ItemGroup><ItemGroup>
36.      <InternalsVisibleTo Include="MyTestProject" />
37. </ItemGroup>  {
38. <ItemGroup>
39.      <InternalsVisibleTo Include="MyTestProject" />
40. </ItemGroup><ItemGroup>
41.      <InternalsVisibleTo Include="MyTestProject" />
42. </ItemGroup><ItemGroup>
43.      <InternalsVisibleTo Include="MyTestProject" />
44. </ItemGroup> builder.UseEnvironment(Environments.Production);
45. <ItemGroup>
46.      <InternalsVisibleTo Include="MyTestProject" />
47. </ItemGroup><ItemGroup>
48.      <InternalsVisibleTo Include="MyTestProject" />
49. </ItemGroup>  }).CreateClient(new WebApplicationFactoryClientOptions() { BaseAddress = new Uri("http://localhost:9000") });
50. <ItemGroup>
51.      <InternalsVisibleTo Include="MyTestProject" />
52. </ItemGroup><ItemGroup>
53.      <InternalsVisibleTo Include="MyTestProject" />
54. </ItemGroup>  var token = TokenHelper.GetToken("username", "password");
55. <ItemGroup>
56.      <InternalsVisibleTo Include="MyTestProject" />
57. </ItemGroup><ItemGroup>
58.      <InternalsVisibleTo Include="MyTestProject" />
59. </ItemGroup>  _client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
60. <ItemGroup>
61.      <InternalsVisibleTo Include="MyTestProject" />
62. </ItemGroup><ItemGroup>
63.      <InternalsVisibleTo Include="MyTestProject" />
64. </ItemGroup>  // Act
65. <ItemGroup>
66.      <InternalsVisibleTo Include="MyTestProject" />
67. </ItemGroup>   }
69. <ItemGroup>
70.      <InternalsVisibleTo Include="MyTestProject" />
71. </ItemGroup>   [Fact]
72. <ItemGroup>
73.      <InternalsVisibleTo Include="MyTestProject" />
74. </ItemGroup>   public async Task V1Legacy_GetDeviceInfoes()
75. <ItemGroup>
76.      <InternalsVisibleTo Include="MyTestProject" />
77. </ItemGroup>   {
78. <ItemGroup>
79.      <InternalsVisibleTo Include="MyTestProject" />
80. </ItemGroup><ItemGroup>
81.      <InternalsVisibleTo Include="MyTestProject" />
82. </ItemGroup>  string url = "url1";
83. <ItemGroup>
84.      <InternalsVisibleTo Include="MyTestProject" />
85. </ItemGroup><ItemGroup>
86.      <InternalsVisibleTo Include="MyTestProject" />
87. </ItemGroup>  // Arrange
88. <ItemGroup>
89.      <InternalsVisibleTo Include="MyTestProject" />
90. </ItemGroup><ItemGroup>
91.      <InternalsVisibleTo Include="MyTestProject" />
92. </ItemGroup>  testOutputHelper.WriteLine($"Testing:{url}");
93. <ItemGroup>
94.      <InternalsVisibleTo Include="MyTestProject" />
95. </ItemGroup><ItemGroup>
96.      <InternalsVisibleTo Include="MyTestProject" />
97. </ItemGroup>  var response = await _client.GetAsync(url);
99. <ItemGroup>
100.      <InternalsVisibleTo Include="MyTestProject" />
101. </ItemGroup><ItemGroup>
102.      <InternalsVisibleTo Include="MyTestProject" />
103. </ItemGroup>  // Assert
104. <ItemGroup>
105.      <InternalsVisibleTo Include="MyTestProject" />
106. </ItemGroup><ItemGroup>
107.      <InternalsVisibleTo Include="MyTestProject" />
108. </ItemGroup>  response.EnsureSuccessStatusCode(); // Status Code 200-299
109. <ItemGroup>
110.      <InternalsVisibleTo Include="MyTestProject" />
111. </ItemGroup><ItemGroup>
112.      <InternalsVisibleTo Include="MyTestProject" />
113. </ItemGroup>  var result = await response.Content.ReadAsStringAsync();
114. <ItemGroup>
115.      <InternalsVisibleTo Include="MyTestProject" />
116. </ItemGroup><ItemGroup>
117.      <InternalsVisibleTo Include="MyTestProject" />
118. </ItemGroup>  var target = JsonSerializer.Deserialize<DeviceInfo>(result, new JsonSerializerOptions { PropertyNameCaseInsensitive = true });
119. <ItemGroup>
120.      <InternalsVisibleTo Include="MyTestProject" />
121. </ItemGroup><ItemGroup>
122.      <InternalsVisibleTo Include="MyTestProject" />
123. </ItemGroup>  Assert.NotNull(target);
124. <ItemGroup>
125.      <InternalsVisibleTo Include="MyTestProject" />
126. </ItemGroup>   }
128. <ItemGroup>
129.      <InternalsVisibleTo Include="MyTestProject" />
130. </ItemGroup>   [Fact]
131. <ItemGroup>
132.      <InternalsVisibleTo Include="MyTestProject" />
133. </ItemGroup>   public async Task V1Legacy_GetCurrent()
134. <ItemGroup>
135.      <InternalsVisibleTo Include="MyTestProject" />
136. </ItemGroup>   {
137. <ItemGroup>
138.      <InternalsVisibleTo Include="MyTestProject" />
139. </ItemGroup><ItemGroup>
140.      <InternalsVisibleTo Include="MyTestProject" />
141. </ItemGroup>  var url = "url2";
142. <ItemGroup>
143.      <InternalsVisibleTo Include="MyTestProject" />
144. </ItemGroup><ItemGroup>
145.      <InternalsVisibleTo Include="MyTestProject" />
146. </ItemGroup>  // Arrange
147. <ItemGroup>
148.      <InternalsVisibleTo Include="MyTestProject" />
149. </ItemGroup><ItemGroup>
150.      <InternalsVisibleTo Include="MyTestProject" />
151. </ItemGroup>  testOutputHelper.WriteLine($"Testing:{url}");
152. <ItemGroup>
153.      <InternalsVisibleTo Include="MyTestProject" />
154. </ItemGroup><ItemGroup>
155.      <InternalsVisibleTo Include="MyTestProject" />
156. </ItemGroup>  var response = await _client.GetAsync(url);
158. <ItemGroup>
159.      <InternalsVisibleTo Include="MyTestProject" />
160. </ItemGroup><ItemGroup>
161.      <InternalsVisibleTo Include="MyTestProject" />
162. </ItemGroup>  // Assert
163. <ItemGroup>
164.      <InternalsVisibleTo Include="MyTestProject" />
165. </ItemGroup><ItemGroup>
166.      <InternalsVisibleTo Include="MyTestProject" />
167. </ItemGroup>  response.EnsureSuccessStatusCode(); // Status Code 200-299
168. <ItemGroup>
169.      <InternalsVisibleTo Include="MyTestProject" />
170. </ItemGroup><ItemGroup>
171.      <InternalsVisibleTo Include="MyTestProject" />
172. </ItemGroup>  var result = await response.Content.ReadAsStringAsync();
173. <ItemGroup>
174.      <InternalsVisibleTo Include="MyTestProject" />
175. </ItemGroup><ItemGroup>
176.      <InternalsVisibleTo Include="MyTestProject" />
177. </ItemGroup>  var target = JsonSerializer.Deserialize<DeviceDataDto>(result, new JsonSerializerOptions {PropertyNameCaseInsensitive = true });
178. <ItemGroup>
179.      <InternalsVisibleTo Include="MyTestProject" />
180. </ItemGroup><ItemGroup>
181.      <InternalsVisibleTo Include="MyTestProject" />
182. </ItemGroup>  Assert.NotNull(target);
183. <ItemGroup>
184.      <InternalsVisibleTo Include="MyTestProject" />
185. </ItemGroup>   }
187. <ItemGroup>
188.      <InternalsVisibleTo Include="MyTestProject" />
189. </ItemGroup>   [Theory]
190. <ItemGroup>
191.      <InternalsVisibleTo Include="MyTestProject" />
192. </ItemGroup>   [InlineData("url3")]
193. <ItemGroup>
194.      <InternalsVisibleTo Include="MyTestProject" />
195. </ItemGroup>   [InlineData("url4")]
196. <ItemGroup>
197.      <InternalsVisibleTo Include="MyTestProject" />
198. </ItemGroup>   public async Task V1Legacy_CheckUrlExist(string url)
199. <ItemGroup>
200.      <InternalsVisibleTo Include="MyTestProject" />
201. </ItemGroup>   {
202. <ItemGroup>
203.      <InternalsVisibleTo Include="MyTestProject" />
204. </ItemGroup><ItemGroup>
205.      <InternalsVisibleTo Include="MyTestProject" />
206. </ItemGroup>  // Arrange
207. <ItemGroup>
208.      <InternalsVisibleTo Include="MyTestProject" />
209. </ItemGroup><ItemGroup>
210.      <InternalsVisibleTo Include="MyTestProject" />
211. </ItemGroup>  testOutputHelper.WriteLine($"Testing:{url}");
212. <ItemGroup>
213.      <InternalsVisibleTo Include="MyTestProject" />
214. </ItemGroup><ItemGroup>
215.      <InternalsVisibleTo Include="MyTestProject" />
216. </ItemGroup>  var request = new HttpRequestMessage(HttpMethod.Head, url);
217. <ItemGroup>
218.      <InternalsVisibleTo Include="MyTestProject" />
219. </ItemGroup><ItemGroup>
220.      <InternalsVisibleTo Include="MyTestProject" />
221. </ItemGroup>  var response = await _client.SendAsync(request);
223. <ItemGroup>
224.      <InternalsVisibleTo Include="MyTestProject" />
225. </ItemGroup><ItemGroup>
226.      <InternalsVisibleTo Include="MyTestProject" />
227. </ItemGroup>  // Assert
228. <ItemGroup>
229.      <InternalsVisibleTo Include="MyTestProject" />
230. </ItemGroup><ItemGroup>
231.      <InternalsVisibleTo Include="MyTestProject" />
232. </ItemGroup>  Assert.NotEqual(404, (int)response.StatusCode);
233. <ItemGroup>
234.      <InternalsVisibleTo Include="MyTestProject" />
235. </ItemGroup>   }
236.     }

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在这个测试中，使用 IClassFixture 进行集成测试，确保同一个类之内的代码共享同一个资源，不同测试方法串行执行。

TIPS: 这里我使用 HEAD 请求来探查给定地址是否存在，ASP. NET CORE 会默认拒绝这个请求（返回406），但是不会提示 404 的错误。

现在的运行时间是这样的：

单类优化

首先研究为什么这个程序花费了如此多的时间执行测试，XUnit 在进行不同 Fact 的测试时，会生成不同的对象，我们已经通过实现 IClassFixture 共享了必要的数据吗？
并没有，XUnit 只是注入了 WebApplicationFactory，而我们在构造函数中执行了很多费时间的操作，包括构造 HttpClient ，获取 token 等。由于获取 token 的函数需要调用外部服务花费了很长的时间，我们可以尝试注入 HttpClient 进行优化。

请注意：大多数情况注入 HttpClient 不是一个好主意，更推荐利用 WebApplicationFactory 对每个测试动态生成 HttpClient 以保证 HttpClient 是初始干净的状态。

我们加入一个新的类：

1.     public class SharedHttpClientFixture : IDisposable
2.     {
3. <ItemGroup>
4.      <InternalsVisibleTo Include="MyTestProject" />
5. </ItemGroup>   public HttpClient Client { get; init; }
7. <ItemGroup>
8.      <InternalsVisibleTo Include="MyTestProject" />
9. </ItemGroup>   public SharedHttpClientFixture()
10. <ItemGroup>
11.      <InternalsVisibleTo Include="MyTestProject" />
12. </ItemGroup>   {
13. <ItemGroup>
14.      <InternalsVisibleTo Include="MyTestProject" />
15. </ItemGroup><ItemGroup>
16.      <InternalsVisibleTo Include="MyTestProject" />
17. </ItemGroup>  WebApplicationFactory<YourAssemblyName.Program> factory = new();
18. <ItemGroup>
19.      <InternalsVisibleTo Include="MyTestProject" />
20. </ItemGroup><ItemGroup>
21.      <InternalsVisibleTo Include="MyTestProject" />
22. </ItemGroup>  
23. <ItemGroup>
24.      <InternalsVisibleTo Include="MyTestProject" />
25. </ItemGroup><ItemGroup>
26.      <InternalsVisibleTo Include="MyTestProject" />
27. </ItemGroup><ItemGroup>
28.      <InternalsVisibleTo Include="MyTestProject" />
29. </ItemGroup> Client = factory.WithWebHostBuilder(builder =>
30. <ItemGroup>
31.      <InternalsVisibleTo Include="MyTestProject" />
32. </ItemGroup><ItemGroup>
33.      <InternalsVisibleTo Include="MyTestProject" />
34. </ItemGroup><ItemGroup>
35.      <InternalsVisibleTo Include="MyTestProject" />
36. </ItemGroup><ItemGroup>
37.      <InternalsVisibleTo Include="MyTestProject" />
38. </ItemGroup>    {
39. <ItemGroup>
40.      <InternalsVisibleTo Include="MyTestProject" />
41. </ItemGroup><ItemGroup>
42.      <InternalsVisibleTo Include="MyTestProject" />
43. </ItemGroup><ItemGroup>
44.      <InternalsVisibleTo Include="MyTestProject" />
45. </ItemGroup><ItemGroup>
46.      <InternalsVisibleTo Include="MyTestProject" />
47. </ItemGroup><ItemGroup>
48.      <InternalsVisibleTo Include="MyTestProject" />
49. </ItemGroup>   builder.UseEnvironment(Environments.Production);
50. <ItemGroup>
51.      <InternalsVisibleTo Include="MyTestProject" />
52. </ItemGroup><ItemGroup>
53.      <InternalsVisibleTo Include="MyTestProject" />
54. </ItemGroup><ItemGroup>
55.      <InternalsVisibleTo Include="MyTestProject" />
56. </ItemGroup><ItemGroup>
57.      <InternalsVisibleTo Include="MyTestProject" />
58. </ItemGroup>    }).CreateClient(new WebApplicationFactoryClientOptions() { BaseAddress = new Uri("http://localhost:9000") });
60. <ItemGroup>
61.      <InternalsVisibleTo Include="MyTestProject" />
62. </ItemGroup><ItemGroup>
63.      <InternalsVisibleTo Include="MyTestProject" />
64. </ItemGroup>  var token = TokenHelper.GetToken("username", "password");
65. <ItemGroup>
66.      <InternalsVisibleTo Include="MyTestProject" />
67. </ItemGroup><ItemGroup>
68.      <InternalsVisibleTo Include="MyTestProject" />
69. </ItemGroup>  Client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token);
70. <ItemGroup>
71.      <InternalsVisibleTo Include="MyTestProject" />
72. </ItemGroup><ItemGroup>
73.      <InternalsVisibleTo Include="MyTestProject" />
74. </ItemGroup>  // Act
75. <ItemGroup>
76.      <InternalsVisibleTo Include="MyTestProject" />
77. </ItemGroup>   }
79. <ItemGroup>
80.      <InternalsVisibleTo Include="MyTestProject" />
81. </ItemGroup>   public void Dispose()
82. <ItemGroup>
83.      <InternalsVisibleTo Include="MyTestProject" />
84. </ItemGroup>   {
85. <ItemGroup>
86.      <InternalsVisibleTo Include="MyTestProject" />
87. </ItemGroup><ItemGroup>
88.      <InternalsVisibleTo Include="MyTestProject" />
89. </ItemGroup>  //throw new NotImplementedException();
90. <ItemGroup>
91.      <InternalsVisibleTo Include="MyTestProject" />
92. </ItemGroup>   }
93.     }

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并修改测试类的签名：

1.     public class ProgramTests : IClassFixture<SharedHttpClientFixture>
2.     {
3. <ItemGroup>
4.      <InternalsVisibleTo Include="MyTestProject" />
5. </ItemGroup>   private readonly ITestOutputHelper testOutputHelper;
6. <ItemGroup>
7.      <InternalsVisibleTo Include="MyTestProject" />
8. </ItemGroup>   private readonly HttpClient _client;
9. <ItemGroup>
10.      <InternalsVisibleTo Include="MyTestProject" />
11. </ItemGroup>   public ProgramTests(SharedHttpClientFixture httpClientFixture, ITestOutputHelper testOutputHelper)
12. <ItemGroup>
13.      <InternalsVisibleTo Include="MyTestProject" />
14. </ItemGroup>   {
15. <ItemGroup>
16.      <InternalsVisibleTo Include="MyTestProject" />
17. </ItemGroup><ItemGroup>
18.      <InternalsVisibleTo Include="MyTestProject" />
19. </ItemGroup>  _client = httpClientFixture.Client;
20. <ItemGroup>
21.      <InternalsVisibleTo Include="MyTestProject" />
22. </ItemGroup><ItemGroup>
23.      <InternalsVisibleTo Include="MyTestProject" />
24. </ItemGroup>  this.testOutputHelper = testOutputHelper;
25. <ItemGroup>
26.      <InternalsVisibleTo Include="MyTestProject" />
27. </ItemGroup>   }

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改完之后，速度提升效果还是非常显著的：

跨类串行

我们多数情况下不会将所有的测试都放在一个类中，对于多个类，我们需要跨类共享。XUnit 使用 ICollectionFixture 支持跨类共享。代码主体拆成两个类，并修改类签名如下：

1.     [Collection("V1 Test Fixture")]
2.     public class ProgramTests
3.     {
4.     ...
5.     }
6.     [Collection("V1 Test Fixture")]
7.     public class UploadTests
8.     {
9.         ....
10.         }

复制代码

我们需要新定义一个类，这个类没有实质性作用，只是作为标识：

1.     [CollectionDefinition("V1 Test Fixture")]
2.     public class TestCollection : ICollectionFixture<SharedHttpClientFixture>
3.     {
4. <ItemGroup>
5.      <InternalsVisibleTo Include="MyTestProject" />
6. </ItemGroup>   // This class has no code, and is never created. Its purpose is simply
7. <ItemGroup>
8.      <InternalsVisibleTo Include="MyTestProject" />
9. </ItemGroup>   // to be the place to apply [CollectionDefinition] and all the
10. <ItemGroup>
11.      <InternalsVisibleTo Include="MyTestProject" />
12. </ItemGroup>   // ICollectionFixture<> interfaces.
13.     }

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我们针对多个类进行测试：

跨类并行（数据不共享）

我们注意到，不同类使用了相同的 Collection 进行标注，因此他们实际上会进行同步调度——上一个执行完成后才会开始执行下一个测试。我们如果使用并行会怎么样呢？显然，修改 Colleciton 会对每个类都生成一次需要注入对象，数据不能直接被共享。

1.     [Collection("V1 Test Fixture1")]    public class ProgramTests    {    ...    }    [Collection("V1 Test Fixture")]    public class UploadTests    {        ....        }        [CollectionDefinition("V1 Test Fixture1")]    public class Test1Collection : ICollectionFixture    {<ItemGroup>
2.      <InternalsVisibleTo Include="MyTestProject" />
3. </ItemGroup>   // This class has no code, and is never created. Its purpose is simply<ItemGroup>
4.      <InternalsVisibleTo Include="MyTestProject" />
5. </ItemGroup>   // to be the place to apply [CollectionDefinition] and all the<ItemGroup>
6.      <InternalsVisibleTo Include="MyTestProject" />
7. </ItemGroup>   // ICollectionFixture interfaces.    }<ItemGroup>
8.      <InternalsVisibleTo Include="MyTestProject" />
9. </ItemGroup>   [CollectionDefinition("V1 Test Fixture")]
10.     public class TestCollection : ICollectionFixture<SharedHttpClientFixture>
11.     {
12. <ItemGroup>
13.      <InternalsVisibleTo Include="MyTestProject" />
14. </ItemGroup>   // This class has no code, and is never created. Its purpose is simply
15. <ItemGroup>
16.      <InternalsVisibleTo Include="MyTestProject" />
17. </ItemGroup>   // to be the place to apply [CollectionDefinition] and all the
18. <ItemGroup>
19.      <InternalsVisibleTo Include="MyTestProject" />
20. </ItemGroup>   // ICollectionFixture<> interfaces.
21.     }

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初始化语句会被执行两次，我们实现了并行，但是数据并不是共享的。（大多数情况下已经够用了。）

跨类并行（数据共享）

由于任务并行无法得知其他任务的工作状态，这个时候数据共享可能会引入很多线程问题（竞争、死锁等），因此不太建议在这种情况下进行共享，我最终也是使用的并行不共享的方式实现。如果我们非得这么用，也不是不行，我们需要小心处理线程同步问题，以互斥锁为例：

1. public class SharedHttpClientFixture : IDisposable
2.     {
3. <ItemGroup>
4.      <InternalsVisibleTo Include="MyTestProject" />
5. </ItemGroup>   private static HttpClient _httpClient;
6. <ItemGroup>
7.      <InternalsVisibleTo Include="MyTestProject" />
8. </ItemGroup>   public HttpClient Client => GetClient();
10. <ItemGroup>
11.      <InternalsVisibleTo Include="MyTestProject" />
12. </ItemGroup>   private HttpClient GetClient()
13. <ItemGroup>
14.      <InternalsVisibleTo Include="MyTestProject" />
15. </ItemGroup>   {
16. <ItemGroup>
17.      <InternalsVisibleTo Include="MyTestProject" />
18. </ItemGroup><ItemGroup>
19.      <InternalsVisibleTo Include="MyTestProject" />
20. </ItemGroup>  if (_httpClient == null) Init();
21. <ItemGroup>
22.      <InternalsVisibleTo Include="MyTestProject" />
23. </ItemGroup><ItemGroup>
24.      <InternalsVisibleTo Include="MyTestProject" />
25. </ItemGroup>  return _httpClient;
26. <ItemGroup>
27.      <InternalsVisibleTo Include="MyTestProject" />
28. </ItemGroup>   }
31. <ItemGroup>
32.      <InternalsVisibleTo Include="MyTestProject" />
33. </ItemGroup>   public static Mutex count = new();
35. <ItemGroup>
36.      <InternalsVisibleTo Include="MyTestProject" />
37. </ItemGroup>   public SharedHttpClientFixture()
38. <ItemGroup>
39.      <InternalsVisibleTo Include="MyTestProject" />
40. </ItemGroup>   {
42. <ItemGroup>
43.      <InternalsVisibleTo Include="MyTestProject" />
44. </ItemGroup>   }
46. <ItemGroup>
47.      <InternalsVisibleTo Include="MyTestProject" />
48. </ItemGroup>   private void Init()
49. <ItemGroup>
50.      <InternalsVisibleTo Include="MyTestProject" />
51. </ItemGroup>   {
52. <ItemGroup>
53.      <InternalsVisibleTo Include="MyTestProject" />
54. </ItemGroup><ItemGroup>
55.      <InternalsVisibleTo Include="MyTestProject" />
56. </ItemGroup>  count.WaitOne();
57. <ItemGroup>
58.      <InternalsVisibleTo Include="MyTestProject" />
59. </ItemGroup><ItemGroup>
60.      <InternalsVisibleTo Include="MyTestProject" />
61. </ItemGroup>  if(_httpClient == null)
62. <ItemGroup>
63.      <InternalsVisibleTo Include="MyTestProject" />
64. </ItemGroup><ItemGroup>
65.      <InternalsVisibleTo Include="MyTestProject" />
66. </ItemGroup>  {
67.                                 ...
68. <ItemGroup>
69.      <InternalsVisibleTo Include="MyTestProject" />
70. </ItemGroup><ItemGroup>
71.      <InternalsVisibleTo Include="MyTestProject" />
72. </ItemGroup>  }
73. <ItemGroup>
74.      <InternalsVisibleTo Include="MyTestProject" />
75. </ItemGroup><ItemGroup>
76.      <InternalsVisibleTo Include="MyTestProject" />
77. </ItemGroup>  count.ReleaseMutex();
78. <ItemGroup>
79.      <InternalsVisibleTo Include="MyTestProject" />
80. </ItemGroup>   }
82. <ItemGroup>
83.      <InternalsVisibleTo Include="MyTestProject" />
84. </ItemGroup>   public void Dispose()
85. <ItemGroup>
86.      <InternalsVisibleTo Include="MyTestProject" />
87. </ItemGroup>   {
88. <ItemGroup>
89.      <InternalsVisibleTo Include="MyTestProject" />
90. </ItemGroup><ItemGroup>
91.      <InternalsVisibleTo Include="MyTestProject" />
92. </ItemGroup>  //throw new NotImplementedException();
93. <ItemGroup>
94.      <InternalsVisibleTo Include="MyTestProject" />
95. </ItemGroup>   }
96. }

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这样多个类型使用静态变量实现了共享，并利用互斥锁保证初始化只执行一次。

由于引入了线程同步机制，这种情况下，并行测试并不一定意味着性能会更好，实际上往往还会更差。

生命周期

XUnit 对共享的数据类型执行以下策略：

• 对 IClassFixture，类的第一个测试方法执行之前，会对注入对象进行初始化。随后每一个方法都会生成测试的类的新对象，并将注入对象传递给他们，在测试类中所有测试方法执行完毕后销毁。
  
• 对 ICollectionFixture，多个类中执行的第一个测试方法之前会对注入对象进行初始化。随后每一个方法都会生成测试类的新对象，并且将注入对象传递给他们，在所有测试类的最后一个方法执行完毕之后销毁。
  

Program 可见性

默认情况下 Program 是其他项目不可见的，这样会导致 WebApplicationFactory 提示错误。.NET 6 开始引入了 minimal API，我的项目是升级而来，并没有使用到这个东西，所以 Program 类是对外可见的。

1.     public class Program
2.     {
3. <ItemGroup>
4.      <InternalsVisibleTo Include="MyTestProject" />
5. </ItemGroup>   static void Main(string[] args)
6. <ItemGroup>
7.      <InternalsVisibleTo Include="MyTestProject" />
8. </ItemGroup>   {
9. <ItemGroup>
10.      <InternalsVisibleTo Include="MyTestProject" />
11. </ItemGroup><ItemGroup>
12.      <InternalsVisibleTo Include="MyTestProject" />
13. </ItemGroup>  var builder = WebApplication.CreateBuilder(args);
14. <ItemGroup>
15.      <InternalsVisibleTo Include="MyTestProject" />
16. </ItemGroup><ItemGroup>
17.      <InternalsVisibleTo Include="MyTestProject" />
18. </ItemGroup>  builder.WebHost.UseUrls("http://*:9000");
19. <ItemGroup>
20.      <InternalsVisibleTo Include="MyTestProject" />
21. </ItemGroup><ItemGroup>
22.      <InternalsVisibleTo Include="MyTestProject" />
23. </ItemGroup>  ConfigureServices(builder.Services, builder.Configuration);
24. <ItemGroup>
25.      <InternalsVisibleTo Include="MyTestProject" />
26. </ItemGroup><ItemGroup>
27.      <InternalsVisibleTo Include="MyTestProject" />
28. </ItemGroup>  var app = builder.Build();
29. <ItemGroup>
30.      <InternalsVisibleTo Include="MyTestProject" />
31. </ItemGroup><ItemGroup>
32.      <InternalsVisibleTo Include="MyTestProject" />
33. </ItemGroup>  Configure(app);
34. <ItemGroup>
35.      <InternalsVisibleTo Include="MyTestProject" />
36. </ItemGroup><ItemGroup>
37.      <InternalsVisibleTo Include="MyTestProject" />
38. </ItemGroup>  app.Run();
39. <ItemGroup>
40.      <InternalsVisibleTo Include="MyTestProject" />
41. </ItemGroup>   }
42.     }

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如果使用 Minimal API，那么你需要在项目文件中对测试项目公开可见性。

1. <ItemGroup>
2.      <InternalsVisibleTo Include="MyTestProject" />
3. </ItemGroup>

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或者在 Program.cs 的最后加上一行。

1. var builder = WebApplication.CreateBuilder(args);
2. // ... Configure services, routes, etc.
3. app.Run();
4. + public partial class Program { }

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注意事项

在 Microsoft.VisualStudio.TestPlatform.TestHost 命名空间也有一个 Program 类，如果你自己实现自定义类型，由于默认引用，不注意就使用了这个东西，而不是你 API 的 Program 类，这样会导致测试无法运行，提示：“找不到 testHost.dep.json”这样的错误，所以尽量使用带命名空间的限定名称。
结论

在 XUnit 测试中，可以使用 IClassFixture 与 ICollectionFixture 来进行数据共享，对于相同类之间的测试会默认进行的串行测试，对不同类之间共享数据的情况，也会进行串行调用。对于在不同类的测试，推荐使用不共享数据的并行测试，数据共享越多，造成状态不一致的风险就越大，因此建议有限制地使用测试数据共享。

请注意，XUnit 不会统计注入对象的初始化时间，而且多次运行测试时间会有一些区别，因此本文中列出的时间仅供参考。

拓展阅读

如果觉得自带的方注入方式满足不了你的要求，那么可以考虑使用第三方类库实现的支持 XUnit 的依赖注入容器。请关注这个项目： pengweiqhca/Xunit.DependencyInjection: Use Microsoft.Extensions.DependencyInjection to resolve xUnit test cases. (github.com)

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