Unit Testing: Why? What? & How?

5) Unit Testing: Why? What? & How?
There are various levels of testing:
• Unit Testing
• Integration Testing
• System Testing
• There are various types of testing based upon the intent of testing such as:
• Acceptance Testing
• Performance Testing
• Load Testing
• Regression Testing
• Based on the testing Techniques testing can be classified as:
• Black box Testing
• White box Testing
How does Unit Testing fit into the Software Development Life Cycle?
This is the first and the most important level of testing. As soon as the programmer develops a unit of code the unit is tested for various scenarios. As the application is built it is much more economical to find and eliminate the bugs early on. Hence Unit Testing is the most important of all the testing levels. As the software project progresses ahead it becomes more and more costly to find and fix the bugs.
In most cases it is the developer’s responsibility to deliver Unit Tested Code.
Unit Testing Tasks and Steps:
Step 1: Create a Test Plan
Step 2: Create Test Cases and Test Data
Step 3: If applicable create scripts to run test cases
Step 4: Once the code is ready execute the test cases
Step 5: Fix the bugs if any and re test the code
Step 6: Repeat the test cycle until the “unit” is free of all bugs
What is a Unit Test Plan?
This document describes the Test Plan in other words how the tests will be carried out.
This will typically include the list of things to be Tested, Roles and Responsibilities, prerequisites to begin Testing, Test Environment, Assumptions, what to do after a test is successfully carried out, what to do if test fails, Glossary and so on
What is a Test Case?
Simply put, a Test Case describes exactly how the test should be carried out.
For example the test case may describe a test as follows:
Step 1: Type 10 characters in the Name Field
Step 2: Click on Submit
Test Cases clubbed together form a Test Suite
Test Case Sample
Test Case ID Test Case Description Input Data Expected Result Actual Result Pass/Fail Remarks
Additionally the following information may also be captured:
a) Unit Name and Version Being tested
b) Tested By
c) Date
d) Test Iteration (One or more iterations of unit testing may be performed)
Steps to Effective Unit Testing:
1) Documentation: Early on document all the Test Cases needed to test your code. A lot of times this task is not given due importance. Document the Test Cases, actual Results when executing the Test Cases, Response Time of the code for each test case. There are several important advantages if the test cases and the actual execution of test cases are well documented.
a. Documenting Test Cases prevents oversight.
b. Documentation clearly indicates the quality of test cases
c. If the code needs to be retested we can be sure that we did not miss anything
d. It provides a level of transparency of what was really tested during unit testing. This is one of the most important aspects.
e. It helps in knowledge transfer in case of employee attrition
f. Sometimes Unit Test Cases can be used to develop test cases for other levels of testing
2) What should be tested when Unit Testing: A lot depends on the type of program or unit that is being created. It could be a screen or a component or a web service. Broadly the following aspects should be considered:
a. For a UI screen include test cases to verify all the screen elements that need to appear on the screens
b. For a UI screen include Test cases to verify the spelling/font/size of all the “labels” or text that appears on the screen
c. Create Test Cases such that every line of code in the unit is tested at least once in a test cycle
d. Create Test Cases such that every condition in case of “conditional statements” is tested once
e. Create Test Cases to test the minimum/maximum range of data that can be entered. For example what is the maximum “amount” that can be entered or the max length of string that can be entered or passed in as a parameter
f. Create Test Cases to verify how various errors are handled
g. Create Test Cases to verify if all the validations are being performed
3) Automate where Necessary: Time pressures/Pressure to get the job done may result in developers cutting corners in unit testing. Sometimes it helps to write scripts, which automate a part of unit testing. This may help ensure that the necessary tests were done and may result in saving time required to perform the tests



31 March 2009 at 08:33

Great post. Unit testing, whether it is automated or manual, is critical to the success of any software project. I have seen too many teams accept poor unit testing and have the mentality of "throwing it over the wall at QA". Never acceptable.

If you have a chance, take a look at my recent post on unit testing nd let me know what you think:



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