xUnit.net Extensibility Brad Wilson Jim Newkirk

Schedule Assert Extensibility9:00 Before/After Extensibility9:45 Fact Extensibility10:15 BREAK10:45 Fixture Extensibility11:00 Runner Extensibility11:30 Putting it all Together11:45

Assert Extensibility

Not Easy to Add New Asserts  Limitations of the platform & language  Provide core assertions with the framework  Keep “assert language” consistent  No differentiation between failure and exceptions

Customization of Comparisons  IEquatable / IEqualityComparer  Assert.Contains  Assert.Equal  IComparable / IComparer  Assert.InRange  Fallback for Contains & Equal

Asserts that Return Values  When type is tested  Assert.IsAssignableFrom  Assert.IsType  Assert.Throws  When collections are tested  Assert.Single  Exception catcher  Record.Exception

Example Compare dates without times

Exercise Finish by 9:45

Before/After Extensibility

Design  Cross-cutting concerns  Reusable attribute  Initializing environment  Cleaning up after stateful tests  Runs regardless of test outcome  Has no access to test class or method  Unspecified order (compose for guarantee)

Example Rollback database

Brainstorming Exercise Finish by 10:15

Fact Extensibility

Design  Answers: “What is a test method?”  Enumeration of tests  Execution of tests  Metadata (skip, timeout, display name)

Why?  Metadata changes  “I want all my tests to have a timeout”  “I want the display name of my test to be something other than method name”  Enumeration changes  “I want this test method to be run many times, perhaps with different input values for each run”  Execution changes  “I want to do something different than just running the method with no parameters”

Example [Theory] attribute

Exercise Followed by break, back by 11:00

Fixture Extensibility

IUseFixture  Share reusable fixture setup and teardown  Constructor  Dispose  Most frameworks encourage base classes here  Lack of multiple inheritance in the CLR  “Inherit to be reused, not to reuse”

Example Test data seed & cleanup

ITestClassCommand and RunWith  Answers: “What is a test class?”  Pre- and post-fixture behavior  Pre- and post-test behavior  Test class creation & cleanup  Test method discovery  Test method ordering

Example Remove Randomization

Exercise Finish by 11:30

Runner Extensibility

Design  Version resilient runner APIs  Link against xunit.runner.utility.dll, not xunit.dll  Test assembly lives in a separate app domain  Assembly  Configuration File  (Optional) Shadow Copy

Low-Level API  Exector (remote)  ExecutorWrapper (local)  On the wire, it’s:  XML as a string (for status)  Boolean continue flag (to cancel)  Don’t use this.

High-Performance API  Thin wrapper on top of ExecutorWrapper  TestRunner  TestRunnerResult  IRunnerLogger  Cracks the XML into simple values  Not stateful; callback is mandatory  Runners: MSBuild, TD.NET, Resharper

Object-Oriented API  Object model on top of ExecutorWrapper  MultiAssemblyTestEnvironment  TestAssembly, TestClass, TestMethod  TestStatus  ITestMethodRunnerCallback  Cracks the XML into objects  Stateful; callback is optional  Runners: Console, GUI

Project files (.xunit)  One or more assemblies  Output types & locations  Filters

Example xunit.console

Putting it all Together

Example BDD with [Observation]

Example BDD with SubSpec

Example Amalga Best Practice Analyzer

Exercise

Thank @xunit