ClassUnder Test 2: Range
The next examples use a different class under test.
Range is a bean that contains two properties, upper and lower.
Because this is for demonstration purposes only,
it is not a complete implementation of a range abstraction.
However, there are two aspects to this class
that make it very interesting for testing.
First, it has a method, isWithin, that takes an
item as an argument and returns true or false,
depending upon whether the argument was below,
between (inclusive), or above the end points
of the range.
Because this presents interesting boundary
conditions, it makes for a good test demonstration.
The second interesting feature of this class
is that it is generic: the types of the upper
and lower bounds can be any type, provided that
they are Comparable.
(The fact that these types are Comparable is
essential to the implementation of the isWithin method.)
Here is the Range class, abbreviated.
package org.springunit.examples;
public class Range<T extends Comparable<T>> {
/**
* Create range with <code>upper</code>
* and <code>lower</code> bounds.<br/>
* @param upper Upper bound of range
* @param lower Lower bound of range
*/
public Range(T upper, T lower) {
setUpper(upper);
setLower(lower);
}
/**
* Is item between upper and lower
* bounds?
*/
public boolean isWithin(T item) {
return item.compareTo(this.lower) >= 0 && item.compareTo(this.upper) <= 0;
}
/**
* Lower bound of range.<br/>
* @param lower New lower bound
*/
public void setLower(T lower) {
this.lower = lower;
}
/**
* Upper bound of range.<br/>
* @param upper New upper bound
*/
public void setUpper(T upper) {
this.upper = upper;
}
private T lower;
private T upper;
}
The fact that the Range class accepts generic parameters
means that the same algorithm can be applied to different data types.
It's a good idea to test such a class with different data types.
In Example 4, we will create a test of the Range class
where the upper and lower bounds are of type
org.springunit.examples.CompositeDateTime.
in Example 5, we will create a second test of the Range class
where the bounds are instances of java.util.GregorianCalendar.
We will limit our testing to the isWithin method.
There are five cases that we should cover:
- the item is below the lower bound
- the item is equal to the lower bound
- the item is between but not equal to the bounds
- the item is equal to the upper bound
- the item is above the upper bound
