SUT - System Under Test
CUT - Class Under Test
Unit - Unit of Work / Use Case
A unit of work is the sum of actions that take place between the invocation of a public method in the SUT and a single noticeable end result by a test of that system.
An end result can be observed without looking at the internal state of the system and only through its public APIs and behavior
An end result is any of:
A unit of work means that it can span as little as a single method and up to multiple classes and functions to achieve purpose.
A unit test is an automated piece of code that invokes a unit of work being tested, and then checks some assumptions about a single end result of that unit. It can be written and run quickly, it is trustworthy, readable, and maintainable. It is consistent in its end results as long as production code has not changed.
It should be:
It should:
When it fails, should be easy to detect what the issue is
A regression is 1+ units of work that once worked, but now don’t
Refactoring means changing a piece of code without changing its functionality – aiming to make it easier to maintain, read, debug, etc.
The convention of a test case:
(unitOfWorkName)(ScenarioUnderTest)(ExpectedBehavior)
Unit of Work Name - name of method or group of methods or classes being tested
Scenario - conditions under which the unit is tested
Expected Behavior - what you expect the tested method to do under the specified conditions.
The test has to read effortlessly
You almost never use tearDown methods in a unit test - if you do, it usually indicates it is at the integration test level
Exercising the SUT and checking the validity of the return value
also called State Verification, determines whether the exercised method worked correctly by examining the changed behavior of the SUT and its collaborators (dependencies) after the method is exercised.
Checking whether an object calls other objects correctly
External Dependency is an object in your system that your SUT interacts with and over which you have no control
A stub is a controllable replacement for an existing dependency (or collaborator) in the system. By using a stub, you can test your code without dealing with the dependency directly.
seams are places in your code where you can plug in different functionality, such as stub classes, adding a constructor parameter, adding a public settable property, etc.
a fake is a generic term used to describe a stub or mock object.
Wide Faking - ability to fake multiple methods at once
An integration test is test that exercises unit of work without having full control over all of it and using one or more of its real dependencies, i.e. time, network, database, threads, random number generators, etc.
Integration Test qualities:
e.g. test uses the real file system or database to perform its work.