Generic API Test tool

By

Moshe Sapir

Almog Masika

Agenda

Testing practice in the industry The Automatic API test tool concept Attributes supplied to the developer Test coverage Design and implementation Tool demonstration

Testing practice in the industry

Testing software module requires deep understanding of the module’s inner logic and its interfaces’ semantics

Currently, dedicated tests are written to each software component

Usually the tests do not try to retrieve functional information from the module’s code

Changes in the software logic are resulted in changes in the test automation logic

Automatic API Test Tool Concept

Enable the developer to add metadata to the modules code

Use .NET attributes to represent the metadata

The metadata should contain information which will enable automatic testing of the module

Create automatic test tool that given the module and attributes can generate tests

Generic API Test Tool

Tested Module

Tested Code

Test Results

Attributes supplied to the developer – Function level attributes

Input-Output Assertion:– Assertion is defined by three expressions

<P, Q, L>

– If P is true before the function is run, then Q is true after the function is run, or one of the exceptions in L is thrown during execution

– For double Sqrt(double x) the developer will define: P: x > 0 Q: ret ^ 2 = x L = {DivisionByZero }

Attributes supplied to the developer – Function level attributes (cont)

Input Parameters attribute– Provide set of interesting assignments to the

methods parameters– For double tan(double x) the developer will

define the following assignments: X = pi X = 0 X = pi/2 X = -1234.45*pi

Attributes supplied to the developer – Class level attributes

Class Instances– Provide set of interesting instances of the class– For class Int32 the developer will define the following

instances: 0 1 -1 2^31 (-2^31) + 1 12345 -780

Attributes supplied to the developer – Class level attributes (cont)

Class Invariants– Define set of Boolean expressions that should be true after and

before executing any member function on an instance of the class– For Account class:

class Account {string Owner;int Balance;

}

The developer will define: Owner != string.Empty Balance >= 0

Test Coverage – Method level coverage

General test– Run the method as many times as possible, using

parameters supplied by the developer. If no parameters were supplied, try to generate the them

Input – Output Assertion test– For each <P, Q, L> defined on the method, try to find an

assignment that satisfies P, run the method and validate Q and L.

Test Coverage – Assembly level coverage

Function call composition– Try to build a call graph of the functions in

the assembly and generate the call paths. Validate input-output assertions and class invariants during the calls:

For the classes:A, B, C, D And the functions:

M1: A x B -> A M2: B x C -> D M3: A x D -> A Build the following graph:

A B C D

M1 M2

M3

Design and implementation – Functional decomposition

Test Attributes- Attributes that are available to the assembly developer.

User Interface- Retrieve from the user the input required to run the test and to present him the test results.

Test Engine- Responsible to run the tests and produce the test results.

Results Reporting: Responsible to save the results in persistent file and redirect them to the graphic user interface.

Tester User Interface

Test Engine Result Reporting

Test Attributes

Design and implementation – Functional decomposition

Data flow between the different components:

User Interface

Result ReportingTest Engine

Test Parmeters

Test Results

Processed Results

Test Engine Design: The Algorithm design pattern

+Run()

-TestedMethod

FunctionRunner

TestMatrix

+Generate() : TestMatrix

MatrixGenerator

+ExecuteTest()

-TestParameters-MatGenerator : MatrixGenerator-FuncRunner : FunctionRunner

TestExecuter

-TestedMethod

MethodTester-TestedClass

ClassTester

-TestedAssembly

AssemblyTester

GeneralMethodTester

InputOutputAssertionsTester

ConstCorrectnessTester

1

1

1

1 -Generates1

*

-Consume

1 *

ObjectBehaviorTester FunctionCompositionTester

+Execute(in TestParameter)

-ExecutersList-TestFinishedEvent

TestEngine

1

Test Attributes Hierarchy

System.Attribute

MethodAttribute

ClassAttribute

-Q-P-L

InputOutputAssertion

-AssingmenstList

InputParameters

-IsConst : bool

Const

-InvariantList

Invariants

-MethodCallSequence

ObjectBehavioure

-InterestingInstances

Instances

Design and implementation – User Interface Structure

-TestEngine

CmdLineParser

-TestEngine-TestResultsBox-AssemblyTreeView

MainWindow

AssmeblyTreeViewTestResultBox

TestParametersDialog

1

1

1

1

1 *

TestEngine

1

1

1

1

User Interface Component

Test Engine Component

Test execution sequence diagram

MainWindow InputOutputAssertionTesterTestEngine

ExecuteTest

ExcelReporterUIReporter

HandleTestResults(TestResult)

HandleTestResults(TestResult)

UpdateUI

UpdateFile

MatrixGenerator

Generate

FunctionRunner

Run

Execute(TespParams)

SetTestParams(TesParams)

Demonstration

. . .

Conclusions

.NET attributes can be used to keep information that will enable automatic testing of software

The technique we have shown is limited to platforms that allow introduction of Meta data in the binary code (.NET, Java)

The Syntax of defining expressive test attributes can be error prone (mainly due to the use of strings as function identifiers)

The ability of such tools to verify large scale software is still to be investigated. Currently is seems can be used as first tire testing (BVT).