Now that we've gotten your first unit tests to run, let's introduce one more way to write tests: using theories. You may have wondered why your first unit tests use an attribute named [Fact] rather than one with a more traditional name like Test. When describing the difference between facts and theories, we like to say:.
A good example of this is testing numeric algorithms. Let's say you want to test an algorithm which determines whether a number is odd or not. If you're writing the positive-side tests odd numbers , then feeding even numbers into the test would cause it fail, and not because the test or algorithm is wrong.
Let's add a theory to our existing facts including a bit of bad data, so we can see it fail :. Although we've only written 3 test methods, the test runner actually ran 5 tests; that's because each theory with its data set is a separate test. Note also that the runner tells you exactly which set of data failed, because it includes the parameter values in the name of the test.
The Test Explorer UI even shows a new level in the tree, as each row of data becomes a test result underneath its test method. Sometimes, you want to write tests and ensure they run against several target application platforms.
The xUnit. NET Core 1. NET 5. With a single test project, we can have our tests run against multiple target frameworks. Open the. When you change a project file from TargetFramework to TargetFrameworks or back , Visual Studio might show you a yellow "alert bar" which indicates that you have to reload the project for your changes to take effect.
It's best to make this kind of change from a clean environment with no dirty text editors, to prevent the possibility of losing any changes. Test Explorer supports any combination of. NET Core including. NET Framework targets. Net and a Console runner for accomplishing the Unit test.
It includes the excellent extensibility of test classes and test methods. Net programming languages like C , VB. Net, and F. Let us explore the bad practices and shortcomings with other. Net Unit testing frameworks as well as improvements with xUnit:. Net Unit test frameworks. It allows you to create new attributes to control your tests. It uses the [Fact] attribute in place of [Test] attribute. The Fact attribute abides Ignore attribute with the new attribute called Skip.
Fact tests invariant conditions and is typically used when there is a need to have a Unit test, which includes no method arguments. Here is an example of [Fact] attribute. As a part of enforcing cleaner code, xUnit requires specifying the reason for skipping a certain test, and it is not mandatory with the former Ignore attribute.
Theory attribute is meant to support data-driven tests that only work with a certain set of values passed as arguments to the test methods. Here is an example:. Theory attribute is a good example of the extensibility feature of xUnit.
If you code a single Unit test method, the [Theory] attribute allows you to execute the method multiple times. For example, let us explore the same code with multiple inputs:. Here the test will run thrice in the test explorer - executing once for each set of specified input.
Benefit: This feature proves the xUnit is far more extensible and allows you to run your test methods multiple times. In xUnit, test methods are isolated, while they interfere with each other in the remaining. Net Unit testing frameworks.
Consider the following examples:. Though both Unit test code appears almost the same, you can find the difference by observing their result update:. Throws : Assert. Test method extensibility. The definition of how to run a test method can be extended. There are two example of this: the first, in xunitext.
Test class extensibility. The definition of run to run a test class can be extended. There is an example of this in xunitext. Version independent runner support. All of the runners in v1. This means that they have no dependencies on xunit.
They will utilize the version of xunit. Third party runner authors are highly encouraged to use the version independent runner support library xunit. Tests in xUnit are split up into Facts and Theories, both specified using an Attribute. A Fact is a regular test, like using the [Test] attribute in MSTest, and it should be used when you expect the same result from the test no matter the input. The [Theory] attribute is used to mark a test as data-driven, which you can provide with parameters on each run.
This is great for when you want to test the same method with many different inputs to confirm that it holds up. You use the [InlineData] attribute with a Theory to send it data.
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