Software testing techniquesSoftware testing techniques

Sandwich strategy

Presentation on the seminar

Kaunas University of Technology

Content

• Sandwich strategy what‘s that?• How does it work?• Pros and cons• Modified Sandwich strategy what‘s that?• How does it work?• Pros and cons

Sandwich strategy what‘s that?

• It‘s a combination of top down and bottom up testing strategies.

• It‘s purpose is compromise usage of top down and bottom up strategies .

How does it work?

• The system is view as having three layers– A target layer in the middle– A layer above the target– A layer below the target– Testing converges at the target layer

• How do you select the target layer if there are more than 3 layers?– Heuristic: Try to minimize the number of stubs and

drivers

How does it work? (2)

How does it work? (3) A

B C D

GFE

Layer I

Layer II

Layer IIITest E

Test D,G

Test B, E, F

Test A, B, C, D,

E, F, G

Test F

Test G

Test A

BottomLayerTests

TopLayerTests

Test A,B,C, D

Bottom up testing

Top down

Pros and Cons of Sandwich Testing

• Top and Bottom Layer Tests can be done in parallel.

• Does not test the individual subsystems thoroughly before integration.

• Solution: Modified sandwich testing strategy.

Modified Sandwich Testing Strategy

• It‘s a better version of Sandwich Testing Strategy.

How does it work?

• Test in parallel:– Middle layer with drivers and stubs– Top layer accessing middle layer (top layer replaces

drivers)– Bottom accessed by middle layer (bottom layer

replaces stubs)

How does it work? (2)A

B C D

GFE

Layer I

Layer II

Layer III

Test F

Test E

Test B

Test G

Test D

Test A

Test C

Test B, E, F

TripleTest ITriple

Test I

Test D,G

DoubleTest II

DoubleTest II

DoubleTest I

DoubleTest I

Test A,C

Test A, B, C, D,

E, F, G

Pros and Cons of Modified Sandwich Testing

• Takes less time than top down and bottom up testing. Because they are used partial.

• It still needs drivers and stubs.

Questions

• Sandwich strategy what‘s that?• How many layers system has in Sandwich

strategy?• How do you select the target layer if there are

more than 3 layers?• What‘s better Sandwich strategy or Modified

sandwich strategy? Why?