COMP1210 Project: Tetrahedron with JUnit Tests – Part 1 


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Overview: This project consists of two classes: (1) Tetrahedron is a class representing a Tetrahedron
object and (2) TetrahedronTest class is a JUnit test class which contains one or more test methods for
each method in the Tetrahedron class. Note that there is no requirement for a class with a main
method in this project.

You should create a new folder to hold the files for this project. After you have created your file, you should create a jGRASP project and add your file; you
should see it in the Source Files category of the Project section of the Browse tab. With this project is
open, your test file,, will be automatically added to the project when it is
created; you should see it in the Test Files category. If appears in source File
category, you should right-click on the file and select “Mark As Test” from the right-click menu.

You will then be able to run the test file by clicking the JUnit run button on the Open Projects toolbar.

Requirements: Create a Tetrahedron class that stores the label and edge, which is non-negative
(>= 0). The Tetrahedron class also includes methods to set and get each of these fields, as well as
methods to calculate the height, surface area, and volume of a Tetrahedron object, and a method
to provide a String value that describes a Tetrahedron object.

The Tetrahedron class includes a
one static field (or class variable) to track the number of Tetrahedron objects that have been
created, as well appropriate static methods to access and reset this field. And finally, this class
provides a method that JUnit will use to test Tetrahedron objects for equality as well as a method
required by Checkstyle.

A regular tetrahedron is a tetrahedron in which all four faces are equilateral triangles
with edge length a. When lying on one face, the tetrahedron is a pyramid with height h.

The variables are
abbreviated as
a is edge length
h is height
A is surface area
V is volume

Design: The Tetrahedron class has fields, a constructor, and methods as outlined below.
(1) Fields: Instance Variables – label of type String and edge of type double. Initialize the
String to “” and the double variable to 0 in their respective declarations. These instance
variables should be private so that they are not directly accessible from outside of the
Tetrahedron class, and these should be the only instance variables (fields) in the class.
Class Variable – count of type int should be private and static, and it should be initialized to

(2) Constructor: Your Tetrahedron class must contain a public constructor that accepts two
parameters (see types of above) representing the label and edge length. Instead of assigning
the parameters directly to the fields, the respective set method for each field (described
below) should be called since they are checking the validity of the parameter. For example,
instead of using the statement label = labelIn; use the statement
setLabel(labelIn); The constructor should increment the class variable count each
time a Tetrahedron is constructed.

Below are examples of how the constructor could be used to create Tetrahedron objects.
Note that although String and numeric literals are used for the actual parameters (or
arguments) in these examples, variables of the required type could have been used instead of
the literals.

Tetrahedron example1 = new Tetrahedron(“Small Example”, 0.5);
Tetrahedron example2 = new Tetrahedron(” Medium Example “, 12.8);
Tetrahedron example3 = new Tetrahedron(“Large Example”, 97.36);

(3) Methods: Usually a class provides methods to access and modify each of its instance
variables (known as get and set methods) along with any other required methods. The
methods for Tetrahedron, which should each be public, are described below. See the
formulas in the figure above and the Code and Test section below for information on
constructing these methods.

o getLabel: Accepts no parameters and returns a String representing the label field.
o setLabel: Takes a String parameter and returns a boolean. If the String
parameter is not null, then the “trimmed” String is set to the label field and the
method returns true. Otherwise, the method returns false and the label is not set.

o getEdge: Accepts no parameters and returns a double representing the edge field.
o setEdge: Takes a double parameter and returns a boolean. If the double
parameter is non-negative, then the parameter is set to the edge field and the method
returns true. Otherwise, the method returns false and the edge field is not set.

o height: Accepts no parameters and returns the double value for the height of the
Tetrahedron. [Be sure to avoid integer division in your expression.]
o surfaceArea: Accepts no parameters and returns the double value for the total
surface area of the Tetrahedron.

o volume: Accepts no parameters and returns the double value for the volume of the
Tetrahedron. [Be sure to avoid integer division in your expression.]

o toString: Returns a String containing the information about the Tetrahedron object
formatted as shown below, including decimal formatting (“#,##0.0##”) for the double
values. Newline and tab escape sequences should be used to achieve the proper layout
within the String but it should not begin or end with a newline.

In addition to the field
values (or corresponding “get” methods), the following methods should be used to
compute appropriate values in the toString method: height(), surfaceArea(),
and volume(). Each line should have no trailing spaces (e.g., there should be no
spaces before a newline (\n) character).

The toString value for example1,
example2, and example3 respectively are shown below (the blank lines are not part
of the toString values).

Tetrahedron “Small Example” with six edges of length 0.5 has:
height = 0.408 units
surface area = 0.433 square units
volume = 0.015 cubic units
Tetrahedron “Medium Example” with six edges of length 12.8 has:
height = 10.451 units
surface area = 283.779 square units
volume = 247.152 cubic units
Tetrahedron “Large Example” with six edges of length 97.36 has:
height = 79.494 units
surface area = 16,418.057 square units
volume = 108,761.565 cubic units

o getCount: A static method that accepts no parameters and returns an int representing
the static count field.
o resetCount: A static method that returns nothing, accepts no parameters, and sets the
static count field to zero.

o equals: An instance method that accepts a parameter of type Object and returns false if
the Object is a not a Tetrahedron; otherwise, when cast to a Tetrahedron, if it has the
same field values as the Tetrahedron upon which the method was called, it returns true.

Otherwise, it returns false. Note that this equals method with parameter type Object will
be called by the JUnit Assert.assertEquals method when two Tetrahedron objects are
checked for equality.

Below is a version you are free to use.
public boolean equals(Object obj) {
if (!(obj instanceof Tetrahedron)) {
return false;
else {
Tetrahedron d = (Tetrahedron) obj;
return (label.equalsIgnoreCase(d.getLabel())
&& Math.abs(edge – d.getEdge()) < .000001);

o hashCode(): Accepts no parameters and returns zero of type int. This method is
required by Checkstyle if the equals method above is implemented.

Code and Test: As you implement the methods in your Tetrahedron class, you should compile it and then
create test methods as described below for the TetrahedronTest class.

Requirements: Create a TetrahedronTest class that contains a set of test methods to test each of
the methods in Tetrahedron.

Design: Typically, in each test method, you will need to create an instance of Tetrahedron, call
the method you are testing, and then make an assertion about the expected result and the actual
result (note that the actual result is commonly the result of invoking the method unless it has a
void return type).

You can think of a test method as simply formalizing or codifying what you
could be doing in jGRASP interactions to make sure a method is working correctly. That is, the
sequence of statements that you would enter in interactions to test a method should be entered
into a single test method.

You should have at least one test method for each method in
Tetrahedron, except for associated getters and setters which can be tested in the same method.
Collectively, these test methods are a set of test cases that can be invoked with a single click to
test all of the methods in your Tetrahedron class.

Code and Test: Since this is the first project requiring you to write JUnit test methods, a good
strategy would be to begin by writing test methods for those methods in Tetrahedron that you
“know” are correct. By doing this, you will be able to concentrate on the getting the test methods

That is, if the test method fails, it is most likely due to a defect in the test method itself
rather the Tetrahedron method being testing. As you become more familiar with the process of
writing test methods, you will be better prepared to write the test methods as new methods are

Be sure to call the Tetrahedron toString method in one of your test methods and
assert something about the return value. If you do not want to use assertEquals, which would
require the return value match the expected value exactly, you could use assertTrue and check
that the return value contains the expected value.

For example, for Tetrahedron example3:
Assert.assertTrue(example3.toString().contains(“\”Large Example\””));

Also, remember that you can set a breakpoint in a JUnit test method and run the test file in Debug
mode. Then, when you have an instance in the Debug tab, you can unfold it to see its values or
you can open a canvas window and drag items from the Debug tab onto the canvas.

The Grading System
When you submit and, the grading system will use the results of
your test methods and their level of coverage of your source files as well as the results of our reference
correctness tests to determine your grade. In this project, your test file should provide at least method
coverage. That is, each method must be called at least once in a test method.