Statement Coverage Testing

Statement Coverage is a white-box testing technique used to verify that every executable statement in a program is executed at least once during testing. It helps ensure that the written code is properly tested and improves software reliability.

Executes all program statements at least once
Helps identify untested code
Improves software quality and reliability

Statement Coverage

Statement Coverage measures the percentage of executable statements that have been tested in a program. It checks whether each statement has been executed during the testing process.

Formula

Statement coverage = (Number of executed statements / Total number of statements in source code) * 100

How It Works

Consider this function:

Python

def get_discount(price, is_member):
    discount = 0                          # S1
    if is_member:                         # S2
        discount = price * 0.10          # S3
    if price > 100:                       # S4
        discount += price * 0.05         # S5
    return price - discount              # S6

Test Case	is_member	price	Statements Hit
T1	True	150	S1, S2, S3, S4, S5, S6
T2	False	50	S1, S2, S4, S6

With both tests, all 6 statements are covered 100% statement coverage.

Step-by-Step Working

Test cases are designed based on the internal code logic
Each test case executes specific statements in the program
Coverage is calculated by comparing executed statements with total statements
Multiple test cases may be required to achieve 100% coverage

What It Catches vs. Misses

Catches:

Dead code (unreachable statements)
Unexecuted branches due to missing tests
Basic logic errors that crash execution

Misses:

False conditions — an if branch being False doesn't need a test
Logical errors in conditions (e.g., > vs >=)
Combinations of conditions
Missing else clauses

Example 1:

Read A
Read B
if A > B
Print “A is greater than B”
else
Print "B is greater than A"
endif

Flowchart

Case 1:

If A = 7, B= 3
No of statements Executed= 5
Total statements= 7
Statement coverage= 5 / 7 * 100
= 71.00 %

Case 2:

If A = 4, B= 8
No of statements Executed= 6
Total statements= 7
Statement coverage= 6 / 7 * 100
= 85.20 %

Coverage Hierarchy

Statement coverage is the weakest in the hierarchy of code coverage techniques because it only checks whether each statement is executed. Higher coverage techniques provide more thorough testing of program logic and execution paths.

Statement < Branch < Condition < Path Coverage
(Weakest) (Strongest)

Level	What’s Measured
Statement Coverage	Each statement executes at least once
Branch Coverage	Each decision outcome (True/False) is tested
Condition Coverage	Each Boolean condition is evaluated
Path Coverage	Every possible execution path is tested

Advantages of Statement Coverage

Easy to understand and implement
Helps identify dead and unused code
Improves overall code quality
Useful during unit testing

Limitations of Statement Coverage

Does not test all decision or branch outcomes
Cannot detect logical errors in conditions
100% statement coverage does not guarantee bug-free software
Some execution paths may remain untested

Usage of Statement Coverage

During unit testing
For small and medium-sized modules
When analyzing test completeness
In early stages of development

Statement Coverage Testing