Test Levels

See unit, integration, system, and acceptance tests as one ladder.

Big Picture

One small picture can make this idea easier to hold.

Small tests

• Fast to run.
• Narrow scope.
• Easy to isolate.
• Find local bugs.

Big tests

• Slower to run.
• Wide scope.
• More real flow.
• Find end-to-end bugs.

VerdictUse both. Small tests are quick, big tests show the full path.

How It Moves

Short steps make the flow easier to see.

1

Unit

Check one small piece.

Integration

Check pieces working together.

System

Check the full product flow.

4

Acceptance

Check if the user goal is met.

Step By Step

This is the same idea, stretched across time.

1. 1

   Code changes

   A small part is updated.

2. 2

   Unit tests

   The piece is checked alone.

3. 3

   Integration tests

   The parts meet and are checked.

4. 4

   System and acceptance

   The whole path is checked for the user.

One Small Model

Think of this like a tiny card you can keep in your pocket.

Test ladder

4 fields

Unit:"One small piece"

Integration:"The links between parts"

System:"The full product flow"

Acceptance:"The user goal"

Quick Check

Question 1 of 10 correct

Which level checks how parts work together?

UnitIntegrationAcceptanceSmoke

HintSubmit

Map It

One more picture helps you see where this lesson matters most.

Scope vs speed

Run speed

Fast

Small and fast

Unit test

Large and slow

Acceptance test

Small and slow

Rare deep check

Large and fast

Quick system smoke

Slow

SmallLarge

Scope

Final Quiz

Question 1 of 30 correct

Which test level is the smallest?

UnitIntegrationSystemAcceptance

HintSubmit