Lab 2: C++ Class Review, TDD Review

Due: 4/12 11:59pm

1 Goals

By the time you have finished this lab, you should have demonstrated your ability to use a simple Test-Driven Development framework (similar to last week's lab, and possibly from CS16 and 24 labs) to write the methods of a simple C++ class with getter methods.

2 Getting Started

This lab may be done solo, or in pairs.

Before you begin working on the lab, please decide if you will work solo or with a partner. If you decide to work with a partner, read the Working in pairs section of the course webpage.

Once you and your partner are in agreement, choose an initial driver and navigator, and have the driver log into their account.

3 Copying some programs from my directory

Visit the following web link—you may want to use "right click" (or "control-click" on Mac) to bring up a window where you can open this in a new window or tab:

You should see a listing of several C++ programs. We are going to copy those into your ~/cs32/lab2 directory all at once with the following command:

cp ~emre/public_html/cs32/code/lab2/* cs32/lab2

Note: If you get the error message:

cp: target '/cs/student/youruserid/cs32/lab2' is not a directory

then it probably means you didn't create a ~/cs32/lab2 directory yet. So do that first.

The * symbol in this command is a "wildcard"—it means that we want all of the files from the source directory copy be copied into the destination directory namely ~/cs32/lab2.

After doing this command, if you cd into ~/cs32/lab2 and use the ls command, you should see several files in your ~/cs32/lab2 directory–the same ones that you see if you visit the link

If so, you are ready to move on to the next step.

If you don't see those files, go back through the instructions and make sure you didn't miss a step. If you still have trouble, ask your TA for assistance.

4 Step 2: Understanding the Starting Point Code

4.1 Understanding the Makefile

In this week's Makefile, you'll see a few things:

CXXFLAGS = -Wall -Wextra -Wno-unused-parameter -Wno-unused-private-field

# Change to this before final submission:
# CXXFLAGS = -Wall -Wextra -Werror

These are the "flags" used when compiling. The -Wno-unused-parameter -Wno-unused-private-field flags are used here because we are doing "test-driven development", and you are starting with "stub code".

Stub code is code that is the minimal amount of code needed to both (a) compile and (b) definitely fail all of the tests. It makes sure that your tests report failure when the code is definitely broken. It is a way of "testing the tests."

In stub code, you sometimes have unused parameters, and unused data members (a.k.a. private fields). We want the compiler to shut up already about those, because we expect that.

Before you turn in your code though, you want to change up the compiler flags to say: if there is any problem at all, tell me about it. Treat warnings as hard errors that prevent compilation. So, be sure to change this flag as indicated in the comments before you make your final submission.

Side node: We use -Werror in this class because we use the same compiler version throughout the class. In a real-world production environment, this is not good software engineering practice: when you update your compiler, the compiler may emit different warnings you did not account for; or if somebody else is trying to compile your code with a different version of the compiler, they may get unexpected warnings turning into hard errors.


BINARIES=testStudent1 testStudent2 testStudent3

This is a variable that contains a list of the three test programs that we are running this week to test your code. Note that the variable BINARIES is used in several places in the Makefile:

  • In the all: to say that by default, we want to make all of these executable programs (i.e.┬ábinaries).
  • After tests: to say that we want make tests to depend on those binaries being compiled and linked—note that we then run each of them in turn to actually test our code.
  • In the clean: rule to say that make clean should remove all of the binaries in addition to removing all of the .o files.

There are other things in the Makefile such as the $^ syntax, and the $@. Notice all of these things, and figure out how this Makefile works. A good reference explaining some of the Makefile syntax seen here is Note that this focuses on compiling C programs, but is still (mostly) relevant for our purposes.

4.2 Understanding the Student class: Student.h and Student.cpp

Then, look over the Student.h and Student.cpp files.

You'll see that the Student.h file contains the specification of a simple C++ class to represent a Student. We will be using this class in a future lab as the basis of a Roster of students, and we'll be working with various sorting and hashing algorithms on this Student class.

For this week's lab though, we just want to focus on simple test-driven development of the constructor, getters and a toString function.

The only file this week where you will be making changes is Student.cpp

4.3 Understanding the tests: testStudent*.cpp and tddFuncs.*

What you should do next is to look through the test cases in testStudent1.cpp, testStudent2.cpp and testStudent3.cpp. These files use a simple test-driven development framework defined in tddFuncs.h and tddFuncs.cpp.

Look over these files and understand how they work. Then, type make tests to compile and run all of the tests.

You can also type, for example, make testStudent1 and ./testStudent1 to make and run these tests one at a time.

When you are ready, start editing Student.cpp, replacing the stubs for the constructor first, and then each of the stubs for the other functions.

4.3.1 Tip: A special note about the toString function

Note that in the case of the toString function, a correct implementation is already provided, but commented out.

This example can be used as the basis for writing similar toString functions in future labs. This is the only time we will provide an example of this technique, so please study it well, and if you have questions about it, please ask.

5 Step 3: Make all the test cases pass

Make the test cases pass by replacing the stubs in Student.cpp with working code. This is the only file you should need to change.

6 Step 4: Checking your work before submitting

When you are finished, you should be able to type make clean and then make tests and see the following output:

-bash-4.2$ make tests
clang++ -Wall -Wextra -Wno-unused-parameter -Wno-unused-private-field   -c -o testStudent1.o testStudent1.cpp
clang++ -Wall -Wextra -Wno-unused-parameter -Wno-unused-private-field   -c -o Student.o Student.cpp
clang++ -Wall -Wextra -Wno-unused-parameter -Wno-unused-private-field   -c -o tddFuncs.o tddFuncs.cpp
clang++ testStudent1.o Student.o tddFuncs.o -o testStudent1
clang++ -Wall -Wextra -Wno-unused-parameter -Wno-unused-private-field   -c -o testStudent2.o testStudent2.cpp
clang++ testStudent2.o Student.o tddFuncs.o -o testStudent2
clang++ -Wall -Wextra -Wno-unused-parameter -Wno-unused-private-field   -c -o testStudent3.o testStudent3.cpp
clang++ testStudent3.o Student.o tddFuncs.o -o testStudent3
Testing class Student...
PASSED: s1.getPerm()
Testing class Student...
PASSED: s1.getLastName()
PASSED: s1.getFirstAndMiddleNames()
Testing class Student...
PASSED: s1.getFullName()
PASSED: s1.toString()

At that point, you are ready to try submitting on the Gradescope system.

7 Submitting via Gradescope

The lab assignment "Lab 2" should appear in your Gradescope dashboard in CMPSC 32. If you haven't submitted anything for this assignment yet, Gradescope will prompt you to upload your files.

For this lab, you will need to upload your modified file (i.e. Student.cpp). You either can navigate to your file, "drag-and-drop" them into the "Submit Programming Assignment" window, or even use a GitHub repo to submit your work.

If you already submitted something on Gradescope, it will take you to their "Autograder Results" page. There is a "Resubmit" button on the bottom right that will allow you to update the files for your submission.

For this lab, if everything is correct, you'll see a successful submission passing all of the autograder tests.

Remember to add your partner to Groups Members for this submission on Gradescope if applicable. At this point, if you worked in a pair, it is a good idea for both partners to log into Gradescope and check if you *can see the uploaded files for Lab 2.

Author: Mehmet Emre


The material for this class is based on Prof. Richert Wang's material for CS 32