Unit 2.2: White Box Testing Fundamentals

1. Structural Testing (White Box Testing)

Definition: White Box Testing (also called Glass Box, Clear Box, or Structural Testing) is a method where the internal code structure is known to the tester. The tester validates the system by checking the actual logic pathways.

Why "White/Glass Box"? The box is transparent. You can see the variables, loops, and logic branches inside.

Need for White Box Testing: Black box testing can tell you that a feature failed, but White Box testing tells you why and where. It is essential only to:

1. Verify Logic: Ensure all logical decisions (True/False) are tested.
2. Find Hidden Errors: Such as memory leaks, uninitialized variables, or dead code that black box testing might miss.
3. Optimize Code: Removing redundant lines or inefficient loops.

Static vs Dynamic White Box:

• Static: Code Review, Walkthrough (Reading code).
• Dynamic: Unit Testing (Running code with inputs).

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2. Path Testing and Basic Path Testing

Definition: Path testing is a structural testing method that involves using the source code of a program to find every possible executable path.

Concept of "Independent Path": An independent path is any path through the program that introduces at least one new set of processing statements or a new condition.

• Ideally, we want to test all independent paths (Basis Path Testing).
• If we test all independent paths, we guarantee that every statement and every branch has been executed at least once.

Coverage Criteria Hierarchy:

1. Statement Coverage: Execute every line of code. (Weakest).
2. Branch Coverage: Execute every "True" and "False" side of an if. (Better).
3. Path Coverage: Execute every unique route through the code. (Best).

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3. DD-Paths (Decision-to-Decision Paths)

Definition: A DD-Path is a sequence of statements that, once entered, must be executed to completion. It represents a single node in a Control Flow Graph (CFG).

Why do we need it? Real code is messy. DD-Paths simplify code into a clean graph model (Nodes and Edges) which allows us to calculate complexity mathematically.

Characteristics:

• It starts at an entry node or decision node.
• It ends at an exit node or decision node.
• It contains no internal branching (no 'if' or 'while' inside the path itself).