COMP1213 - Project - Tetrahedron with JUnit Tests – Part 2 - Solved

•    Tetrahedron.java, TetrahedronTest.java  

 

Specifications  
Overview:  In this project, the two files developed in Part 1 are to be extended as follows: (1) Tetrahedron, which is a class representing a Tetrahedron object, will implement the Comparable interface and (2) TetrahedronTest class, which is a JUnit test class, will be expanded from method coverage to condition coverage for Tetrahedron.  The new items for Part 2 are underlined below for your convenience.  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 and add your files from Part 1

(Tetrahedron.java file and TetrahedronTest.java).  You should create a new jGRASP project for Part 2 and add Tetrahedron.java file and TetrahedronTest.java to the project; you should see the two files in their respective categories – Source Files and Test Files.  If TetrahedronTest.java 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.

 

        •    Tetrahedron.java (new items for this class in Part 2 are underlined) 

 

Requirements: Create a Tetrahedron class that stores the label and edge, where edge is nonnegative (>= 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. In addition, Tetrahedron must implement the Comparable interface for objects of type Tetrahedron.

 

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.  

(Source: https://en.wikipedia.org/wiki/Tetrahedron)
 
  
 

The variables are abbreviated as follows: 

 

a is edge length 

 

h is height 

 

A is surface area 

 

V is volume 

 
 

 

  
 
 

Design:  The Tetrahedron class implements the Comparable interface for objects of type Tetrahedron and has fields, a constructor, and methods as outlined below (last method is new).

 

(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 zero.  

 

(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.

 

o    compareTo: Accepts a parameter of type Tetrahedron and returns an int as follows: a negative value if this.volume() is less than the parameter’s volume; a positive value if this.volume() is greater than the parameter’s volume; zero if the two volumes are essentially equal.  For a hint, see the activity for this module. 

 

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.   

 

•     TetrahedronTest.java  

 

Requirements: Create a TetrahedronTest class that contains a set of test methods to test each of the methods in Tetrahedron.  The goal for Part 2 is method, statement, and condition coverage.

       

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 sufficient test methods so that each method, statement, and condition in Tetrahedron are covered.  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: 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 correct.  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 developed.  Be sure to call the Tetrahedron toString method in one of your test cases so that the grading system will consider the toString method to be

“covered” in its coverage analysis.  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.  You can also step-in to the method being called by the test method and then single-step through it, looking for the error.