尝试对基于.NET EF Core的通用存储库进行单元测试在处理DbContext.Entry时失败

huangapple
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英文:

Trying to Unit Test Generic Repository based on .NET EF Core fails when dealing with DbContext.Entry

问题

I have written a generic repository (BaseRepository<TEntity>), where its Delete method code is:

  1. public virtual void Delete(TEntity entity)
  2. {
  3.     if (dbContext.Entry(entity).State == EntityState.Detached)
  4.     {
  5.         dbContext.Attach(entity);
  6.     }
  7.     dBContext.Remove(entity);        
  8. }

I want to unit-test the code. Since the DbContext is an external dependency, I just want to verify that when I call the Repository.Delete(entity), then eventually the DbContext.Remove(entity) is called once. However, I have to Mock the behavior of dbContext.Entry... just before the actual dbContext.Remove(entity) call.

The Unit Test code is:

  1. [Fact]
  2. public void Delete_SomeEntityToRepository_CallsTheAddMethod_To_DbContext()
  3. {
  4.     // Arrange
  5.     var testObject = new Customer()
  6.     {
  7.         Name = "Test-Customer"
  8.     };
  9.     
  10.     var dbContextMock = new Mock<DbContext>();
  11.     var dbEntityEntryMock = new Mock<EntityEntry<Customer>>();
  12.     
  13.     dbContextMock.Setup(d => d.Entry(testObject)).Returns(dbEntityEntryMock.Object);
  14.     dbEntityEntryMock.Setup(e => e.State).Returns(EntityState.Unchanged);
  15.     
  16.     // Act
  17.     var repository = new CustomerRepository(dbContextMock.Object);
  18.     repository.Delete(testObject);
  20.     // Assert
  21.     dbContextMock.Verify(x => x.Remove(It.Is<Customer>(y => y == testObject)), Times.AtMost(1));
  22. }

However, this code crashes at the line:

  1. dbContextMock.Setup(d => d.Entry(testObject)).Returns(dbEntityEntryMock.Object);

with the message:

Can not instantiate proxy of class: Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry`1[[Fx.CommonTests.DataAccess....

System.ArgumentException
Can not instantiate proxy of class: Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry`1[[Fx.CommonTests.DataAccess.Customer, Fx.CommonTests, Version=4.3.0.0, Culture=neutral, PublicKeyToken=null]].
Could not find a parameterless constructor. (Parameter 'constructorArguments')...

Obviously, the DbContext.Entry(...) is the problem. So, any ideas about how to mock this???

I tried various variants of the code, as found in several articles, about how I can mock such cases, but always the end result was the same. Any ideas?

英文:

I have written a generic repository (BaseRepository<TEntity>), where it's Delete method code is:

  1.     public virtual void Delete(TEntity entity)
  2.     {
  3.         if (dbContext.Entry(entity).State == EntityState.Detached)
  4.         {
  5.             dbContext.Attach(entity);
  6.         }
  7.         dBContext.Remove(entity);        
  8.     }

I want to unit-test the code. Since the DbContext is an external dependency, I just want to verify that when I will call the Repository.Delete(entity), then eventually the DbContext.Remove(entity) is to be called once. However, I have to Mock the behavior of dbContext.Entry... just before the actual dbContext.Remove(entity) call.
The Unit Test code is:

  1.     [Fact]
  2.     public void Delete_SomeEntityToRepository_CallsTheAddMethod_To_DbContext()
  3.     {
  4.         // Arrange
  5.         var testObject = new Customer()
  6.         {
  7.             Name = &quot;Test-Customer&quot;
  8.         };
  9.         
  10.         var dbContextMock = new Mock&lt;DbContext&gt;();
  11.         var dbEntityEntryMock = new Mock&lt;EntityEntry&lt;Customer&gt;&gt;();
  12.         
  13.         dbContextMock.Setup(d =&gt; d.Entry(testObject)).Returns(dbEntityEntryMock.Object);
  14.         dbEntityEntryMock.Setup(e =&gt; e.State).Returns(EntityState.Unchanged);
  15.         
  16.         // Act
  17.         var repository = new CustomerRepository(dbContextMock.Object);
  18.         repository.Delete(testObject);
  20.         //Assert
  21.         dbContextMock.Verify(x =&gt; x.Remove(It.Is&lt;Customer&gt;(y =&gt; y == testObject)), Times.AtMost(1));
  22.     }

However this code crashes, and actually at line:
dbContextMock.Setup(d =&gt; d.Entry(testObject)).Returns(dbEntityEntryMock.Object);
with message:
Can not instantiate proxy of class: Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry`1[[Fx.CommonTests.DataAccess....

System.ArgumentException
Can not instantiate proxy of class: Microsoft.EntityFrameworkCore.ChangeTracking.EntityEntry`1[[Fx.CommonTests.DataAccess.Customer, Fx.CommonTests, Version=4.3.0.0, Culture=neutral, PublicKeyToken=null]].
Could not find a parameterless constructor. (Parameter 'constructorArguments')...

Obviously the DbContext.Entry(...) is the problem. So, any ideas, about how to mock this???

I tried various variants of the code, as found in several articles, about how can I mock such cases, but always the end was the same. Any Ideas?

答案1

得分: 2

这是如何模拟dbcontext以防止测试错误的方法，但我认为在设计这个测试时可能有不同的方法要考虑（请查看下面的“但是”部分）：

  1. using Microsoft.EntityFrameworkCore;
  2. using Microsoft.EntityFrameworkCore.ChangeTracking;
  3. using Microsoft.EntityFrameworkCore.ChangeTracking.Internal;
  4. using Microsoft.EntityFrameworkCore.Metadata;
  5. using Moq;
  7. // ...
  1. [Fact]
  2. public void Delete_SomeEntityToRepository_CallsTheAddMethod_To_DbContext()
  3. {
  4.     // Arrange
  5.     var testObject = new Customer();
  7.     var internalEntityEntry = GetInternalEntityEntry(testObject);
  9.     var dbEntityEntryMock = new Mock&lt;EntityEntry&lt;Customer&gt;&gt;(internalEntityEntry);
  10.     dbEntityEntryMock.Setup(e =&gt; e.State).Returns(EntityState.Unchanged);
  12.     var dbContextMock = new Mock&lt;DbContext&gt;();
  13.     dbContextMock.Setup(d =&gt; d.Entry(testObject)).Returns(dbEntityEntryMock.Object);
  15.     // Act
  16.     var repository = new CustomerRepository(dbContextMock.Object);
  17.     repository.Delete(testObject);
  19.     //Assert
  20.     dbContextMock.Verify(x =&gt; x.Remove(It.Is&lt;Customer&gt;(y =&gt; y == testObject)), Times.AtMost(1));
  21. }
  23. private static InternalEntityEntry GetInternalEntityEntry(Customer testObject)
  24. {
  25.     return new InternalEntityEntry(
  26.         new Mock&lt;IStateManager&gt;().Object,
  27.         new RuntimeEntityType(
  28.             name: nameof(Customer), type: typeof(Customer), sharedClrType: false, model: new(),
  29.             baseType: null, discriminatorProperty: null, changeTrackingStrategy: ChangeTrackingStrategy.Snapshot,
  30.             indexerPropertyInfo: null, propertyBag: false,
  31.             discriminatorValue: null),
  32.         testObject);
  33. }

Full text here: https://gist.github.com/ctrl-alt-d/3d10384a06fa1e0c515e1f182fb83bb0

但（<- 大 "但"）:

  • 您不应该这样做：
    https://github.com/dotnet/efcore/issues/27110
  • 在使用EF时如何编写测试，请阅读：https://learn.microsoft.com/en-us/ef/ef6/fundamentals/testing/mocking
  • 如果我要为您的通用存储库编写测试，我会这样做：https://gist.github.com/ctrl-alt-d/8bc8d1f9e41a8ea98309397c46933fe4
英文:

This is how you can Mock dbcontext to prevent the test error, but I believe that there may be a different approach to consider when designing this test (see but section below):

  1. using Microsoft.EntityFrameworkCore;
  2. using Microsoft.EntityFrameworkCore.ChangeTracking;
  3. using Microsoft.EntityFrameworkCore.ChangeTracking.Internal;
  4. using Microsoft.EntityFrameworkCore.Metadata;
  5. using Moq;
  7. // ...
  1. [Fact]
  2. public void Delete_SomeEntityToRepository_CallsTheAddMethod_To_DbContext()
  3. {
  4.     // Arrange
  5.     var testObject = new Customer();
  7.     var internalEntityEntry = GetInternalEntityEntry(testObject);
  9.     var dbEntityEntryMock = new Mock&lt;EntityEntry&lt;Customer&gt;&gt;(internalEntityEntry);
  10.     dbEntityEntryMock.Setup(e =&gt; e.State).Returns(EntityState.Unchanged);
  12.     var dbContextMock = new Mock&lt;DbContext&gt;();
  13.     dbContextMock.Setup(d =&gt; d.Entry(testObject)).Returns(dbEntityEntryMock.Object);
  15.     // Act
  16.     var repository = new CustomerRepository(dbContextMock.Object);
  17.     repository.Delete(testObject);
  19.     //Assert
  20.     dbContextMock.Verify(x =&gt; x.Remove(It.Is&lt;Customer&gt;(y =&gt; y == testObject)), Times.AtMost(1));
  21. }
  23. private static InternalEntityEntry GetInternalEntityEntry(Customer testObject)
  24. {
  25.     return new InternalEntityEntry(
  26.         new Mock&lt;IStateManager&gt;().Object,
  27.         new RuntimeEntityType(
  28.             name: nameof(Customer), type: typeof(Customer), sharedClrType: false, model: new(),
  29.             baseType: null, discriminatorProperty: null, changeTrackingStrategy: ChangeTrackingStrategy.Snapshot,
  30.             indexerPropertyInfo: null, propertyBag: false,
  31.             discriminatorValue: null),
  32.         testObject);
  33. }

Full text here: https://gist.github.com/ctrl-alt-d/3d10384a06fa1e0c515e1f182fb83bb0

But (<- big "but"):

huangapple
  • 本文由 发表于 2023年6月11日 22:04:07
  • 转载请务必保留本文链接：https://go.coder-hub.com/76450849.html
  • c#
  • entity-framework-core
  • repository-pattern
  • unit-of-work
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