Black Box Testing Technique : Error Guessing

Black Box Testing Technique

If I would like to do software testing, I start with thinking about how to select the test cases. If I have no idea about software's internal algorithm and cannot cover all combinations of input values and preconditions for a module of software because of resource constraint (Time or manpower), I will use Black Box Testing Technique to design the test cases.

Error Guessing

Error Guessing is a software testing technique that generates test cases which can find the error by using past experience of tester. The key concept is using the prior software testing experience to supplement other software testing techniques. 

The known error in any software is varied so using input from experienced tester for that software is a good idea. From my software testing experience, the typical errors are related to "divide by zero" and "various date and time format".

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Black Box Testing Technique : Decision Table Testing

Black Box Testing Technique

If I would like to execute testing a software (testing web or windows application), I start with thinking about how to select the test cases. If I have no idea about software's internal algorithm and cannot cover all combinations of input values and preconditions for a module of software because of resource constraint (Time or manpower), I will use Black Box Testing Technique to design the input values.

Decision Table Testing

Decision Table Testing is a software testing technique that tries to create the complete test cases by using decision table. This decision table will contain all possible values of each input and output. Then, we mark each possible scenario to that decision table.

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Black Box Testing Technique : Pairwise Testing (All-pairs testing) - Part3

Pairwise Testing (All-pairs testing) 

After we have installed CTE XL which is one of software testing tools for Pairwise Testing (All-pairs testing), we will start using it with following scenario.


CTE XL: How to use

I will use this following scenario for test case design in this example.

Scenario

System: Fund Transfer feature in ATM system of A Bank with 3 dependent factors:

1st factor: How to transfer

- A Bank to A Bank

- A Bank to B Bank
2nd factor: Amount of money
- Less than $1.00
- Between $1.00 and $5,000
- More than $5,000
3rd factor: SMS alert?
- Yes
- No

Step

1. Start CTE XL.

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Black Box Testing Technique : Pairwise Testing (All-pairs testing) - Part2

Pairwise Testing (All-pairs testing) 

After you have a clear view in Pairwise Testing (All-pairs testing) technique, I will introduce one of the software testing tools that can help you to design test case by this software testing technique. The software testing tool's name is CTE XL by Berner & Mattner. You can find more information of this software testing tool in link.

CTE XL Set Up Process

1. Click here to open Download Page.

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Black Box Testing Technique : Pairwise Testing (All-pairs testing) - Part1

Black Box Testing Technique

If I would like to execute software testing (web testing or windows application testing), I start with thinking about how to select the test cases. If I have no idea about software's internal algorithm and cannot cover all combinations of input values and preconditions for a module of software because of resource constraint (Time or manpower), I will use Black Box Testing Technique to design the input values.

Pairwise Testing (All-pairs testing) 

Pairwise Testing (All-pairs testing) is a software testing technique that designs test cases for testing all possible combinations of each pair of input parameters. The number of this test cases will be less than testing all possible combinations. You can see more detail in the Part3 of articles. To get the list of test cases for software testing we need to use some algorithm to extract them.

The key idea of this technique for software testing is "the most bugs in a software are introduced by a single input parameter. The next one are introduced by interaction between pairs of input parameters.".

If you have found that many bugs in your software are introduced by two factors and would like to design test cases for software testing by using this condition, Pairwise Testing (All-pairs testing) will be the answer.

Sample Bug: Bug in Fund Transfer feature in ATM system is introduced by 2 conditions:

1st condition: From A Bank to B Bank

2nd condition: More than $5,000

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Now you understand the concept of testing a software (web testing or windows application testing) by using Pairwise Testing (All-pairs testing) testing technique.

Since this software testing technique is hard to do manually, I will share you how to create test cases by tool in the next articles.

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Related topic of Pairwise Testing (All-pairs testing) 

Basic concept: Black Box Testing Technique : Pairwise Testing (All-pairs testing) - Part1
How to install test tool: Black Box Testing Technique : Pairwise Testing (All-pairs testing) - Part2
How to use test tool: Black Box Testing Technique : Pairwise Testing (All-pairs testing) - Part3

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Black Box Testing Technique : Boundary value analysis

Black Box Testing Technique

If I would like to execute testing a software (testing web or windows application), I start with thinking about how to select the test cases. If I have no idea about software's internal algorithm and cannot cover all combinations of input values and preconditions for a module of software because of resource constraint (Time or manpower), I will use Black Box Testing Technique to design the input values.

Boundary value analysis

Boundary value analysis is a software testing technique that selects the input data which represents boundary values. These data includes both boundary and each side of boundary which should be in the smallest increment. 

Example
I would like to test withdrawal on ATM system. The maximum amount is $500 and minimum amount is $1.

Find boundary value:

1. Maximum value is $500
2. Minimum value is $1

Find each side of boundary value

1. $501 and $499 for "Maximum value is $500" case
2. $2 and $0 for "Maximum value is $1" case

The final list of input values are 

1. $501, $499 and $500
2. $2, $0 and $1

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Now you can design and execute testing a software (testing web or windows application) by using Boundary value analysis testing technique. 

Let's find the pairwise testing (All-pairs testing) technique in the next article.

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Black Box Testing Technique : Equivalence partitioning

Black Box Testing Technique

If I would like to execute testing a software (web testing or windows application testing), I start with thinking about how to select the test cases. Then, if I have no idea about software's internal algorithm and cannot cover all combinations of input values and preconditions for a module of software because of resource constraint (Time or manpower), I will use Black Box Testing Technique to design the input values for this software testing.

Equivalence partitioning

Equivalence partitioning is a software testing technique that groups the input data for a module of a software into partitions of data that can represent each possible case. Then, select an input data from each partition.

Example
I would like to execute software testing with withdrawal module on ATM system. The maximum amount is $500 and minimum amount is $1.

Partitioning:

1. More than $500
2. Between $500 and $1
3. Less than $1

Select input data:

1. $800 for "More than $500" case
2. $200 for "Between $500 and $1" case
3. $0 for "Less than $1" case

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Now you can design and execute testing a software (web testing or windows application testing) by using Equivalence partitioning testing technique. 

Let's find the Boundary value analysis testing technique for software testing in the next article.

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