Introduction
Regression testing is an essential part of software development. It ensures that new code changes or updates do not affect existing functionalities being used. This process helps maintain the quality and reliability of a software.
In this article, we will explore different types of regression testing, understand their uses, and see examples where applicable.
Types of Regression Testing
Corrective Regression Testing
Definition: Corrective regression testing is performed when there are no changes in the software's existing functionality. It ensures that the existing test cases still work as expected.
When to Use: Use corrective regression testing when bug fixes or minor changes are made to the software without altering its core features.
Example:
// Initial method
public int add(int a, int b) {
return a + b;
}
// Minor fix (corrective)
public int add(int a, int b) {
if (a == null || b == null) return 0; // Handling null values
return a + b;
}
In this example, the minor fix ensures that the method handles null values without changing the core functionality.
Retest-All Regression Testing
Definition: Retest-all regression testing involves testing all the tests in the test suite. It ensures that every aspect of the application is tested after changes.
When to Use: This method is used when there are significant changes in the software or when the system has been moved to a new environment.
Example: Retest-all regression testing doesn't typically involve code but rather running all test cases in the suite to ensure no functionality is broken.
Selective Regression Testing
Definition: Selective regression testing focuses only on the parts of the software that were modified or are likely to be affected by the changes.
When to Use: Use this method to save time and resources when only a small part of the application is changed.
Example:
// Changed method
public int multiply(int a, int b) {
return a * b;
}
// Selective tests
@Test
public void testMultiply() {
assertEquals(20, multiply(4, 5));
}
In this example, only the test for the modified multiply method is run.
Progressive Regression Testing
Definition: Progressive regression testing is done when there are changes in the software specifications and new test cases need to be created.
When to Use: Use this method when the software requirements change or new features are added.
Example:
// Original method
public int subtract(int a, int b) {
return a - b;
}
// New feature
public int subtract(int a, int b, boolean allowNegative) {
int result = a - b;
return allowNegative ? result : Math.max(result, 0);
}
Here, the new feature allowNegative is added, and new test cases are created to test both the original and the new functionality.
Complete Regression Testing
Definition: Complete regression testing involves retesting the entire application after major changes.
When to Use: This method is used when there are major code changes, updates, or upgrades to the software.
Example: Similar to retest-all, this involves running the full test suite to ensure no issues are introduced after significant updates.
Partial Regression Testing
Definition: Partial regression testing ensures that the changes do not affect the unchanged parts of the software.
When to Use: Use this method when only a portion of the code is changed.
Example:
// Original method
public int divide(int a, int b) {
return a / b;
}
// Changed method (partial)
public int divide(int a, int b) {
if (b == 0) throw new IllegalArgumentException("Division by zero");
return a / b;
}
// Partial tests
@Test
public void testDivide() {
assertEquals(2, divide(4, 2));
assertThrows(IllegalArgumentException.class, () -> divide(4, 0));
}
Here, partial regression testing ensures that division by zero is handled properly without affecting other parts of the code.
Unit Regression Testing
Definition: Unit regression testing focuses on testing individual units or components of the software.
When to Use: Use this method when small units of code are changed or updated.
Example:
// Unit method
public boolean isPositive(int number) {
return number > 0;
}
// Unit test
@Test
public void testIsPositive() {
assertTrue(isPositive(5));
assertFalse(isPositive(-1));
}
In this example, unit regression testing focuses on the isPositive method to ensure it works correctly.
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