The document discusses various topics related to software testing. It defines the purpose of testing as ensuring software systems work as expected by demonstrating their operation through controlled experiments before release. Testing fulfills two purposes: to demonstrate quality and detect/fix problems. It discusses criteria for stopping testing such as reaching resource limits, completing planned activities, or achieving certain test coverage levels. The document also contrasts functional vs structural testing, black-box vs white-box testing, unit vs developer test cases, and introduces test-driven development.

1. Chapter 6

2. 2Md. Masudur Rahman

3. Testing
3
The purpose of software testing is to ensure that the
software systems would work as expected when they
are used by their target customers and users. The most
natural way to show this fulfillment of expectations is to
demonstrate their operation through some “dry-runs” or
controlled experimentation in laboratory settings before
the products are released or delivered. In the case of
software products, such controlled experimentation
through program execution is generally called testing.
Md. Masudur Rahman

4. Testing
To summarize, testing fulfills two primary purposes:
• To demonstrate quality or proper behavior;
• To detect and fix problems.
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5. When or at what defect level to stop
testing?
1. Resource based testing
- “Stop when you run out of time.”
- “Stop when you run out of money.”
2. Plan based testing
- “Stop when you complete planned test activities.”
Others criteria:
3. Coverage based criterion (Developer respective) like
80% of the planning covered
4. Usage based criterion (User respective) like basic
scenarios/requirements covered
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6. Philosophy of Testing
1. Validate the functions is it OK or NOT
OR
2. Find bugs and fix it
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7. Functional vs. Structural Testing
The main difference between functional and structural testing is
the perspective and the related focus:
• Functional testing focus on the external behavior of a software
system or its various components, while viewing the object to
be tested as a black-box that prevents us from seeing the
contents inside.
• On the other hand, structural testing focus on the internal
implementation, while viewing the object to be tested as a
white-box that allows us to see the contents inside.
• The whole software systems can be treated as a “black-box”,
while we focus on the functions or input-output relations instead
of the internal implementation.
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8. BBT vs. WBT
1. WBT is generally used to test small objects, such as small
software products or small units of large software products; while
BBT is generally more suitable for large software systems or
substantial parts of them as a whole.
2. Defects detected through WBT are easier to fix than those
through BBT because of the direct connection between the
observed failures and program units and implementation details
in WBT.
3. WBT may miss certain types of defects, such as omission and
design problems, which could be detected by BBT. In general
BBT is effective in detecting and fixing problems of interfaces
and interactions, while WBT is effective for problems localized
within a small unit.
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9. BBT vs. WBT
4. WBT is used more in early sub-phases of testing for large
software systems, such as unit and component testing, while BBT
is used more in late sub-phases, such as system and acceptance
testing.
5. BBT is typically performed by dedicated professional testers,
and could also be performed by third-party personnel in a setting
of IV&V (independent verification and validation); while WBT is
often performed by developers themselves as code should be
familiar to the developer.
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10. Unit vs. Developer Test Case
Unit Test case:
• A unit can be a function or a class
• Generally written by Tester
Developer Test Case:
• Function basis testing
• Written by Developer
When Unit of Test cases are designed for a function, then Unit Test
case and Developer Test Case are same.
10Md. Masudur Rahman

11. Test Driven Development (TDD)
First write the test case of a
function.
Then write the actual function
and test it to develop the
product.
This process is referred to as
TDD.
@Test
void testAdd(){
Calculator cal = new Calculator();
assertEqual(11,cal.add(5,6));
}
Calculator{
public void add(int a, int b){
return a+b;
}
}
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12. Reference
Book: Software Quality Engineering - Jeff Titan
1204-Oct-14 QA in Context

13. Thank You
13Md. Masudur Rahman