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The tests use a few additional commands defined by JUnit to tell the framework whether
the unit test passes or fails:

assertEquals([String message], expected, actual [, tolerance])
Causes the unit test to fail if expected is not equal to actual. If tolerance is specified, the
equality for floating point numbers is calculated to that tolerance.
assertSame([String message], expected, actual)
Causes the unit test to fail if expected does not refer to the same object as actual.
assertTrue([String message], boolean condition)
Causes the unit test to fail if the Boolean condition evaluates to false.
assertFalse([String message], boolean condition)
Causes the unit test to fail if the Boolean condition evaluates to true.
assertNull([String message], java.lang.Object object)
Causes the unit test to fail if object is not null.
assertNotNull([String message], java.lang.Object object)
Causes the unit test to fail if object is null.
fail([String message])
Causes the unit test to fail immediately.

Each assertion can optionally be given a message. In that case, if the test fails, the message
is displayed in the test report generated by the framework. In JUnit, a test that completes
without failing is considered to have passed.

Every test in JUnit must be able to be run independently of every other test, and the tests
should be able to be run in any order. The individual tests are grouped together into a test
case. Each test is a method in a test case object, which inherits from junit.framework.
TestCase. (The above assert commands are inherited from this class.) Each test case can
optionally have a setUp( ) function, which sets up any objects or values required for the
tests, and a tearDown( ) function, which restores the environment to its condition before
the test was run.

Unit Testing Example

The examples in this section are the individual test methods from a test case object called
testFeeCalculation. There are many tests that would exercise the fee calculation function
shown in the Refactoring section above. This example shows six of them. All of them
require an instance of the FeeCalculation class, which is set up using this setUp( ) function:

public FeeCalculation feeCalculation;
public void setUp( ) {
feeCalculation = new FeeCalculation( );
}
The first test simply verifies that the function has performed its calculation and has gener-
ated the right result by comparing the output to a known value, which was calculated by
hand using a calculator:

158 CHAPTER SEVEN