Sometimes it happens that you should write unit tests… <\/p>\n\n\n\n
Just kidding – you HAVE TO write unit tests (me as well).<\/p>\n\n\n\n
In a perfect world the method we want to write a unit-test for is well-written, concise and returns concrete value. Unfortunately, there are methods that seems to be intricate in terms of unit tests, at least at first glance. Let’s consider the following scenario:<\/p>\n\n\n\n
public class CustomClass\n{\n private readonly ICustomService _customService;\n\n public CustomClass(ICustomService customService)\n {\n _customService = customService;\n }\n\n public void RunProcess(int param_1, int param_2, int param_3)\n {\n _customService.Run(\n descriptorBuilder => descriptorBuilder\n .BuildMyProperty_1(param_1)\n .BuildMyProperty_2(param_2)\n .BuildMyProperty_3(param_3)\n );\n }\n}\n\npublic interface ICustomService\n{\n void Run(Func<IDescriptor, IDescriptor> descriptorBuilder);\n}\n\npublic interface IDescriptor\n{\n public IDescriptor BuildMyProperty_1(int myProperty_1);\n public IDescriptor BuildMyProperty_2(int myProperty_2);\n public IDescriptor BuildMyProperty_3(int myProperty_3);\n}<\/code><\/pre>\n\n\n\nHaving class like this we want to write unit test for the RunProcess<\/code> method. The method accepts three int parameters. Eventually the parameters are passed to the ICustomService.Run<\/code> method that accepts builder-style parameter. Moreover, the RunProcess<\/code> returns nothing. <\/p>\n\n\n\nUnit test using NSubstitute<\/h1>\n\n\n\n
NSubstitute<\/a> might be your best friend when it comes to mock objects and assert received calls. The syntax is succinct and intuitive so I would suggest you to consider to experiment with the library. <\/p>\n\n\n\nLet’s build unit test in a AAA manner – arrange, act, assert – which NSubstitute is designed for.<\/p>\n\n\n\n
The test name is RunProcess_CustomServiceExecutedWithPassedParameters_Success<\/em>.
The name follows the pattern: <MethodNameThatIsBeingTested>_<ExpectedInternalMethodBehaviour>_<Status>.
I guess there are as many test naming conventions as engineers that create it. Furthermore, I believe that as long as the convention informs you well about test internals it is good enough.<\/p>\n\n\n\n The test looks like this:<\/p>\n\n\n\n
[Fact]\npublic void RunProcess_CustomServiceExecutedWithPassedParameters_Success()\n{\n \/\/arrange\n var callParameters = (111, 22, 3333);\n\n var mockDescriptor = Substitute.For<IDescriptor>();\n mockDescriptor.ReturnsForAll<IDescriptor>(mockDescriptor); \n\n var customService = Substitute.For<ICustomService>();\n CustomClass customClass = new CustomClass(customService);\n\n \/\/act\n customClass.RunProcess(\n param_1: callParameters.Item1,\n param_2: callParameters.Item2,\n param_3: callParameters.Item3\n );\n\n \/\/assert\n customService\n .Received(1)\n .Run(Arg.Is<Func<IDescriptor, IDescriptor>>(\n descriptorBuilder => AssertDescriptorFunc(\n descriptorBuilder,\n mockDescriptor,\n callParameters\n )\n )\n );\n}\n\nprivate bool AssertDescriptorFunc(\n Func<IDescriptor, IDescriptor> descriptorFunc,\n IDescriptor mockDescriptor,\n (int, int, int) callParameters\n)\n{\n descriptorFunc(mockDescriptor);\n\n mockDescriptor.Received(1).BuildMyProperty_1(callParameters.Item1);\n mockDescriptor.Received(1).BuildMyProperty_2(callParameters.Item2);\n mockDescriptor.Received(1).BuildMyProperty_3(callParameters.Item3);\n\n return true;\n}<\/code><\/pre>\n\n\n\nLet’s briefly summarize what has happened up there. The test asserts that after the customClass.RunProcess<\/code> invocation the customService.Run<\/code> method received exactly one call. The invocation happened with exactly one parameter. The parameter was type of Func<IDescriptor,IDescriptor><\/code> and then was asserted using AssertDescriptorFunc<\/code> method.<\/p>\n\n\n\nSummary<\/h1>\n\n\n\n
To sum up, thanks to the NSubstitute library we are able to write unit test even for such an unusual scenario. NSubstitute offers much more than I’ve just presented here. I highly recommend to check the NSubstitute documentation and spend some time on playing with its functionalities.<\/p>\n\n\n\n
If you want to give it a try you can find attached scenario in my github<\/a>, project: nsubstitute_1, test project: nsubstitute_1-test.<\/p>\n\n\n\n Have a nice day, bye!<\/p>\n","protected":false},"excerpt":{"rendered":"
Introduction Sometimes it happens that you should write unit tests… Just kidding – you HAVE TO write unit tests (me as well). In a perfect…<\/p>\n