Génération de jeux de testpour les programmes de règles

1er juillet 2009

ILOG Chair of Software EngineeringFreiburg Universität

Bruno Berstelberstel@informatik.uni-freiburg.de

Michel Lecontemichel.leconte@fr.ibm.com

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What does The User want?

• As a user:– I have a program made of a collection of rules– I usually have no specification of this program – I have to write a test suite that covers well the

program

• I want you to:– At least generate the input data for these tests

• with a “good coverage”

– If possible, also generate the expected results

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The rules we talk about

• Condition-Action rules– If the value of the shopping cart is greater than 100, then give a gift to the customer.

– If the subject of the mail contains “enlarge your Rolex”, then mark the mail as junk.

• Made of– A condition (or guard): a formula with variables on an

object model– An action part: assignments, calls to methods of the

object model– Object model = graph of objects with attributes

• Not a tree: beware of aliasing

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What does it mean totest a rule?

And furthermore togenerate tests for a rule?

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A test for one rule

• A rule is a relation– between input states and output states– partial, as the rule may not be executable in some

states

• A test case for a rule is– an initial state (input data)– whether the rule is expected to be executable– if so, the expected resulting state (output data)

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Generating tests for one rule

• To find an initial state where the rule is executable:– Build a logical formula from the rule guard

– Solve the satisfiability of this formula• We use a constraint solver• Plus preferences to choose among multiple solutions

• Are we interested in states where the rule is not executable?– If so, solve the satisfiability of the negation of the guard

• Probably interested in exploring all disjuncts

– To be addressed with respect to the other rules.

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What does it mean totest a rule program?

And furthermore togenerate tests for a rule program?

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What’s the difference?

Gold35 y.o.

Gold65 y.o.

Silver65 y.o.

if the customer category is Gold, then…

if the customer age is greater than 60, then…

r1

r2

r1

r2

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A test suite that “covers well”…

• In absence of overlapping rules– generate one test case for each rule– optionally

• several cases for each rule if it reassures the user• a test for the case where no rule is applicable

• A simple approach to overlaps– disambiguate overlaps– generate one test for each case

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It’s not enough

Gold35 y.o.

Gold65 y.o.

Silver65 y.o.

if the customer category is Gold, then…

if the customer age is greater than 60, then…

r1

r1r2

r2

r1

r2

?s1

s2

s3

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General approach

• Consider the rule combinations and their maximal executions– either as transitions– or as executions– or as execution histories

• These combinations do not overlap (when confluent)– generate one test case for each

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Conclusion

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Conclusion

• Generating one test case for one rule is “easy”.

• Generating a test suite for a rule program involves computing its executions.– Cf. bounded model checking?

• The concept of “coverage” raises the issues of overlapping and confluence.– An overlapping analysis could be helpful to start with– So could a confluence analysis

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Merci