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日期:2021-07-08 09:25

2021/7/6 HW1: Writing Black Box Tests

1/6 HW1: Writing Black Box Tests

Due Tuesday by 11:59pm Points 15

Motivation

This week we took an in depth look at our first testing technique: black box testing. One

of the key elements of black box testing is that the tester does not have access to the source. In

this assignment, you will be given a specification and list of requirements. This will give you

experience writing unit tests in a black box testing scenario.

Course Learning Outcome(s):

Apply testing techniques, including black-box and white-box techniques, automatic testing

activities, and regression testing (CLO 4)

Module Learning Outcome(s):

Apply black box testing techniques

Description

For this assignment, you will be writing unit tests based on the following

specifications/requirements.

You will write a series of unit tests to test a function called credit_card_validator (written for you)

that is passed a sequence of digits as a string that represents a credit card number. This function

will return True if it is a valid credit card number, otherwise, it will return False .

Depending on the credit card issuer, the length of a credit card number can range between 10 and

19 digits. The first few digits of the number are the issuer prefix. Each credit card issuer has an

assigned range of numbers. For example, only Visa credit card numbers may begin with 4 , while

American Express card numbers must begin with either a 34 or 37 . Sometimes, credit card

providers are assigned multiple ranges. For example, MasterCard card numbers must start with the

numbers between 51 through 55 or 2221 through 2720 (inclusive).

The last digit of the number is referred to as the check digit and acts as a checksum. Most credit

cards calculate this check digit using the Luhn algorithm (see resources below for how this is

calculated).

In order to limit the scope of this assignment, we are going to limit the number of credit card issuers

to 3: Visa, MasterCard, and American Express. Each has its own prefixes and length requirements.

Visa

Prefix(es): 4

?

2021/7/6 HW1: Writing Black Box Tests

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Length: 16

MasterCard

Prefix(es): 51 through 55 and 2221 through 2720

Length: 16

American Express

Prefix(es): 34 and 37

Length: 15

Your task is to create a series of tests that attempt to reveal bugs in the implementation. As this is

black box testing, you will not have access to the source so you must use what you have learned

this week to generate test cases.

You will be submitting your code to Gradescope which will auto grade your tests. In order to get full

credit on the assignment, you will need to locate all 6 bugs in the code (refer to the rubric for full

details). Some are easier than others. Bug 5 is easy to miss without using Partition Testing and Bug

6 requires using what you know about common errors to design your tests.

You are free to determine how you generate your test cases. You may do it completely manually, or

use an automated tool like the TSLgenerator. No matter how you generate your test cases, in your

file testing file ( tests.py ), you need to include a comment for each test case describing:

What the test case (i.e. credit card number) is meant to verify

How you determined what to use as the test case

Here is an example:

# Verifies if Master Cards with valid lengths and invalid check bits returns False

# Picked using Category Partition Testing

def test11(self):

self.assertFalse(credit_card_validator("...."))

You also need to ensure you have test cases that do a good job covering the input domain. This

means that at the very least, you need to have a test case for each of the prefix ranges listed

above.

Please submit all your tests, even the ones that do not find bugs. Remember, you are practicing

writing a testing suite, which can be used to test the code again if changes are made. There may

be a situation where a previously passing test fails when someone updates credit_card_validator .

Finally, your test suite needs to be free of linting errors using the PEP8 standard; this will be

important later when working on shared repositories. If you are unfamiliar with linting, please see

the resources below. The easiest way to accomplish this is to ensure that there are no "squiggly"

lines under your code in PyCharm (You will need to change PyCharm's default line length to 79 to

match PEP8). You can also use the PEP8 Online tool below to copy and paste your code to verify it

has no errors.

Restrictions ?

2021/7/6 HW1: Writing Black Box Tests

3/6

For this assignment, you are prohibited from using Random Testing. Yes, Random Testing is a type

of Black Box Testing, but you will be working with this approach in a later module (Exploration:

Random Testing). You will not receive points for any bugs triggered by Random Testing. This

means that you cannot use code to generate the test cases, you need to come up with them

yourself. Please restrict yourself to using other Black Box Testing techniques: Error Guessing,

Partition Testing, and Boundary Value Testing.

Hints You will need to include

if __name__ == '__main__':

unittest.main()

It is best to only have a single assert in any test. Once one fails, the rest of the code in the test

isn't executed.

You may assume only strings of digits are being sent to credit_card_validator

I used the TSLgenerator to create roughly 35 test cases and then picked some to break

Use what you learned about Error Guessing and Boundary Values to find tricky bugs

You will need to use from credit_card_validator import credit_card_validator in your tests.py

To ensure your tests are correctly importing the function for testing, you may put the following

dummy code into a file called credit_card_validator.py

def credit_card_validator(num):

pass

You may submit as many times as you want to Gradescope to check how well your test suite

performs

What to turn in

Submit to Gradescope your testing suite; it must be named tests.py

This file will include at the top of each test a comment describing your test generation

methodology

This file will contain tests that cover all prefix ranges

This file will be free of PEP8 linting errors

Don't remove passing tests, submit them all

Resources

Luhn algorithm (https://en.wikipedia.org/wiki/Luhn_algorithm)

Generate Credit Card Numbers (https://bestccgen.com/)

Luhn Number Checksum (useful when generating valid check digits)

(https://www.dcode.fr/luhn-algorithm)

PEP8 Style Guide (https://www.python.org/dev/peps/pep-0008/)

PEP8 Online (copy and paste your code to check) (http://pep8online.com/) ?

2021/7/6 HW1: Writing Black Box Tests

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Black Box Testing

Linting Python in VS Code (use flake8) (https://code.visualstudio.com/docs/python/linting) ?

2021/7/6 HW1: Writing Black Box Tests

5/6 Total Points: 15

Criteria Ratings Pts

Bug 1 Found 2 pts Full Marks 0 pts No Marks Bug 2 Found 2 pts Full Marks 0 pts No Marks Bug 3 Found 2 pts Full Marks 0 pts No Marks Bug 4 Found 2 pts Full Marks 0 pts No Marks Bug 5 Found 2 pts Full Marks 0 pts No Marks Bug 6 Found 2 pts Full Marks 0 pts No Marks Test Case Methodology Contains a comment for each test case with: * What it is meant to verify * How it was selected 1 pts Full Marks There is a comment for each test case describing: * What it

verifies * How it was selected 0.5 pts Half Marks At least half of the test cases contain comments that describe: * What it

verifies * How it was selected 0 pts No Marks More than half the test cases are missing comments that describe: * What it verifies * How it

was selected Contains tests for each prefix range Contains tests for each prefix range (4, 34, 37, 51-55, and 2221-2720) 1 pts Full Marks All 5 ranges covered 0.5 pts Half Marks At least 3/5 ranges covered 0 pts No Marks Fewer than 3 ranges covered tests.py is free of

linting errors tests.py is free of

linting errors 1 pts Full Marks There are no linting errors 0.5 pts Half Marks There are no more than 2

linting errors 0 pts No Marks There are 3 or more

linting errors ?

2021/7/6 HW1: Writing Black Box Tests


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