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School of
Computer Science
Testing database systems
+ a little bit of slicing
ASTReNet Workshop
David Willmor
Informatics Process Group
School of Computer Science
The University of Manchester
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School of
Computer Science
Database systems
• Program state
– Volatile
– Structured according to a type system
• Database state
– Persistent
– Structured according to a data model
Program 1
Program 2
Database
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School of
Computer Science
START
Database operations
• Interact with database state
– intensional (or extensional)
• Intensional relational algebra
– subset of the database state
read (read)
– subset of the database state
inserted or updated (add)
– subset of the database state
deleted (del)
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Database
Statement
02
Rollback
Statement
03
Commit
Statement
04
07
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08
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• Used for slicing – Willmor, Embury &
Shao ICSM’04
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STOP
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School of
Computer Science
Database dependencies
START
• Slicing
– What a statement is dependent
upon?
– Extra dependencies for database
state (& interactions between
states)
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Database
Statement
02
Rollback
Statement
03
Commit
Statement
04
07
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08
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• Testing
– Define use pairs
– a statement add/deletes and
then another reads
09
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STOP
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School of
Computer Science
The data model (schema)
• Rich store of information about the behaviour of SQL
queries
– INSERT INTO employee VALUES (“bob”, “m”,
“10/06/75”, true);
– SELECT * FROM supervisor;
– CREATE VIEW supervisor AS SELECT * FROM
employee WHERE supervisor = true;
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School of
Computer Science
The data model (schema)
• Another example…
– DELETE FROM reviewing WHERE
reviewingid = 1;
– CREATE TABLE score(…..
FOREIGN KEY (reviewingid) REFERENCES
reviewing(reviewingid) ON DELETE CASCADE);
– Cascading delete
REFERENTIAL INTEGRITY!!
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School of
Computer Science
START
Database transactions
• Logical grouping of database
operations
01
Database
Statement
02
Rollback
Statement
03
Commit
Statement
– Succeed or fail together
• Commit
– Writes each statement to the
database
• Abort/Rollback
– Discards the effect of each
operation
– Database is in state prior to
transaction
04
07
05
08
06
09
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STOP
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School of
Computer Science
Effect of persistence
START
• One execution can effect a
later execution
01
Database
Statement
02
Rollback
Statement
• A use can occur before its
definition!
03
Commit
Statement
• Define—use pairs that exist
over time
04
07
05
08
06
09
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• And further complications…
STOP
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School of
Computer Science
Effect of multiple programs
• Execution of one program
can effect another program
START
01
Database
Statement
02
Rollback
Statement
03
Commit
Statement
START
01
• Each program interacts via
the SAME database state
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02
04
07
05
08
06
04
• Define—use pairs can exist
between programs
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09
07
06
• Programs can access the
database concurrently
10
08
STOP
09
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STOP
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School of
Computer Science
Fixed or evolving database states
• Traditional system… if environment remains
constant (i.e. controlled testing)…
– identical input = identical behaviour
– Key concept of a number of testing practices i.e., Rothermel
& Harrold safe regression test selection
• Fixed database….
– identical input = identical behaviour
• Evolving database…
– identical input != identical behaviour
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School of
Computer Science
What is a test case?
• Test case for database systems:





P – the program under test
i – the application input
o – the application output
Dic – initial database state
Doc – resultant database state
 Database states – extensional or intensional
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School of
Computer Science
Extensional vs intensional states
• Extensional: entire state is specified
– Easy to capture
– Difficult to maintain
– Costly to reason over
• Intensional: description of state is specified
– Difficult to capture
– Easier to maintain
– Cheap to reason over
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School of
Computer Science
Conclusions…
• What are we working on…
– Safe regression test selection for database
systems (submitted for publication)
– Test Adequacy for database systems (submitted for
publication)
– Ordering test cases based on intensional
descriptions (in preparation)
– Testing the future using hypothetical databases
(working on…)
– http://www.cs.man.ac.uk/~willmord/ papers & reports
coming soon….
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School of
Computer Science
Open question
• Can test cases be automatically generated if you
don’t know the database state?
Controversial point
• Source code analysis is more accurate when you
consider the data model
• Real world database state is more useful than
synthetic generated states
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