Testing levels (unit, integration, system, acceptance) in Software Engineering - Step-by-Step Execution

Concept Flow - Testing levels (unit, integration, system, acceptance)

Start Testing

↓

Unit Testing

↓

Integration Testing

↓

System Testing

↓

Acceptance Testing

↓

End

Testing starts with small parts (unit), then checks combined parts (integration), then the whole system, and finally if it meets user needs (acceptance).

Execution Sample

Software Engineering

Test Levels:
1. Unit: Test small parts
2. Integration: Test combined parts
3. System: Test whole system
4. Acceptance: Test user needs

This shows the four main testing levels from smallest to largest scope.

Analysis Table

Step	Testing Level	What is tested?	Purpose	Example
1	Unit Testing	Individual functions or methods	Check if each small part works alone	Test if a function adds two numbers correctly
2	Integration Testing	Groups of combined units	Check if parts work together	Test if login function works with database access
3	System Testing	Complete system	Check if whole system meets requirements	Test if website works on different browsers
4	Acceptance Testing	System from user perspective	Check if system meets user needs and is ready	User tests if app does what they want

💡 All testing levels completed to ensure software quality and readiness

State Tracker

Testing Level	Start	After Step 1	After Step 2	After Step 3	Final
Unit Testing	Not done	Done	Done	Done	Done
Integration Testing	Not done	Not done	Done	Done	Done
System Testing	Not done	Not done	Not done	Done	Done
Acceptance Testing	Not done	Not done	Not done	Not done	Done

Key Insights - 3 Insights

Why do we test small parts first before testing the whole system?

Testing small parts first (unit testing) helps find problems early and makes fixing easier, as shown in step 1 of the execution_table.

What is the difference between system testing and acceptance testing?

System testing checks if the whole system works correctly (step 3), while acceptance testing checks if it meets user needs and is ready to use (step 4).

Can acceptance testing be done before system testing?

No, acceptance testing happens last after system testing ensures the system works, as shown in the flow and execution_table steps.

Visual Quiz - 3 Questions

Look at the execution_table, at which step do we test if parts work together?

A Step 2 - Integration Testing

B Step 1 - Unit Testing

C Step 3 - System Testing

D Step 4 - Acceptance Testing

💡 Hint

Check the 'What is tested?' column in execution_table row 2

According to variable_tracker, which testing level is completed last?

A Integration Testing

B Acceptance Testing

C System Testing

D Unit Testing

💡 Hint

Look at the 'Final' column in variable_tracker for each testing level

If a bug is found in a single function, which testing level should catch it first?

A Acceptance Testing

B System Testing

C Unit Testing

D Integration Testing

💡 Hint

Refer to execution_table step 1 about what unit testing covers

Concept Snapshot

Testing levels:
1. Unit: Test small parts alone
2. Integration: Test combined parts
3. System: Test whole system
4. Acceptance: Test if system meets user needs
Each level builds on the previous to ensure quality.

Full Transcript

Testing software happens in four main levels. First, unit testing checks small parts like functions to make sure they work alone. Next, integration testing checks if these parts work together properly. Then, system testing checks the entire system to see if it meets all requirements. Finally, acceptance testing checks if the system meets user needs and is ready to use. This order helps find problems early and ensures the software is reliable and useful before release.