What is Junit Test Fixture?

A test fixture is a group of objects that are in a fixed state and are used as a baseline for executing tests. Their goal is to guarantee that tests are conducted in a consistent and well-known environment, resulting in reproducible findings.
Fixtures that are examples include:

  • Using a specific, well-known collection of data to populate a database
  • Copying a collection of files that are well-known.
  • Setup/creation of false or mock objects, as well as preparation of incoming data

If a collection of tests uses the same fixtures, you should build the common test fixture using a separate setup code. You can add code inside the test function to generate its own test fixture if a set of tests requires distinct test fixtures.

Junit is a unit testing framework for the Java programming language. JUnit has been important in the development of test-driven development, and is one of a family of unit testing frameworks which is collectively known as xUnit that originated with SUnit.

JUnit is linked as a JAR at compile-time; the framework resides under package junit.framework for JUnit 3.8 and earlier, and under package org.junit for JUnit 4 and later.

A research survey performed in 2013 across 10,000 Java projects hosted on GitHub found that JUnit, was the most commonly included external library. Each library was used by 30.7% of projects.