Conformance Testing with TestNG, Part 1: Essentials


  1. Getting started
  2. Defining a test suite
  3. Test fixtures
  4. Test listeners
  5. Test methods
  6. Test preconditions
  7. Further resources

1 Getting started

The purpose of conformance testing is to determine the extent to which a product satisfies the requirements stipulated in the relevant specifications. In the context of the Open Geospatial Consortium's (OGC) compliance program, it is a kind of “black box” testing that examines only the externally visible characteristics or behaviors of the implementation under test (IUT).

The OGC maintains a testing facility for its members that currently provides access to test suites for more than 20 OGC specifications, some of which are international standards that have been jointly produced with ISO (TC 211, Geographic information/Geomatics). Every OGC specification includes an abstract test suite (ATS) that describes the conformance requirements. The ATS—which generally appears in Annex A—establishes a basis for developing an executable test suite (ETS) that is run to perform a conformity assessment.

The official OGC test harness (TEAM Engine) can execute test suites written using TestNG, a popular Java-based testing framework. A Maven archetype is available to serve as a template for creating a new ETS; it quickly generates a rudimentary test suite that can be run immediately. The source code is hosted at GitHub. Project releases are available in the central Maven repository with these coordinates (using the latest version is always recommended):

groupId: org.opengis.cite
artifactId: ets-archetype-testng
version: 2.5

In order to use the archetype and build the resulting test suite a Java Development Kit (JDK) and Apache Maven must be installed:

  • JDK 17
  • Apache Maven 3.9

To create a new test suite open a command shell (terminal window) and invoke the interactive archetype:generate goal. It is necessary to specify the ets-code property at this point, the value of which must be a legal Java package name. For OGC test suites the convention is to identify the principal specification by major and minor version: wfs20, cat30, and the like. See Listing 1 for a sample invocation where the ets-code value is “abc10”; note that a '' (backslash) character indicates that a line is continued.

Listing 1: Using the archetype interactively

mvn archetype:generate \
    -Dfilter=org.opengis.cite:ets-archetype-testng \

Several prompts will ask for various property values in order to generate the test suite project. The suggested default values may be modified if desired. It is also possible to create a test suite non-interactively in “batch” mode by using the -B flag as shown in Listing 2.

Listing 2: Using the archetype in batch mode

mvn archetype:generate -B \
    -DarchetypeGroupId=org.opengis.cite \
    -DarchetypeArtifactId=ets-archetype-testng \
    -DarchetypeVersion=2.5 \
    -Dets-code=abc10 \
    -DartifactId=ets-abc10 \

The main class, TestNGController, resides in the root package; it implements the TestSuiteController interface declared in the teamengine-spi module. The actual test run arguments are supplied in an XML representation of a Java properties file. Specify the location of this file as a command-line argument or simply put it in your user home directory ($HOME or %USERPROFILE%) and name it “test-run-props.xml”. An example is shown in Listing 3 (see also src/main/config/test-run-props.xml).

Listing 3: Passing test run arguments in a properties file

<?xml version="1.0" encoding="UTF-8"?>
<properties version="1.0">
  <comment>Test run arguments</comment>
  <entry key="iut"></entry>

After an initial test suite has been created, several files must be updated in order to describe the test suite and provide guidance to users:

  • README (/)
  • Javadoc overview (/src/main/javadoc/overview.html)
  • Site content (/src/site/)
  • CTL wrapper script (/src/main/scripts/ctl/)
  • TEAM-Engine configuration file (/src/main/config/teamengine/config.xml)

2 Defining a test suite

The TestNG framework offers considerable flexibility regarding the overall organization of a test suite. A test suite can be conveniently defined by an XML file. Listing 4 shows the test suite definition produced when creating a new test suite from the Maven archetype (it's a resource file located at src/main/resources/org/opengis/cite/${ets-code}/testng.xml).

Listing 4: A test suite definition file

<?xml version="1.0" encoding="UTF-8"?>
<suite name="${ets-code}-${version}" verbose="0" 
  <parameter name="iut"  value=""/>

    <listener class-name="org.opengis.cite.abc10.TestRunListener" />
    <listener class-name="org.opengis.cite.abc10.SuiteFixtureListener" />
    <listener class-name="org.opengis.cite.abc10.TestFailureListener" />

  <test name="Conformance Level 1">
      <package name="org.opengis.cite.abc10.level1" />
  <test name="Conformance Level 2">
      <package name="org.opengis.cite.abc10.level2" />

Each <test> element occurring within a top-level <suite> element denotes a collection of tests that corresponds to a conformance class or level. Each collection contains one or more test classes that focus on a functional area. In a test report the results are typically summarized by conformance class as shown in Figure 1.

Figure 1: TestNG results summary

TestNG results summary

A test class contains test methods that implement the actual test cases. In Listing 4 the test classes are identified implicitly by package name. It is strongly recommended that each conformance class have a corresponding package that contains its constituent test classes. Keep in mind that the test sets (<test> elements) comprising a suite are executed in document order as they occur in the XML suite definition.

It is possible to incorporate tests implemented in other test suites. This is accomplished by simply referring to the external packages or classes in the test suite definition. For example, the WFS 2.0 test suite includes several test classes from the GML 3.2 suite (see Listing 5).

Listing 5: Incorporating tests from other suites

<test name="All GML application schemas">
    <class name="org.opengis.cite.iso19136.general.XMLSchemaTests" />
    <class name="org.opengis.cite.iso19136.general.GeneralSchemaTests" />
    <class name="org.opengis.cite.iso19136.general.ModelAndSyntaxTests" />
    <class name="org.opengis.cite.iso19136.general.ComplexPropertyTests" />

<test name="Simple WFS">
    <package name="org.opengis.cite.iso19142.simple" />

Each test suite is packaged as a standard JAR file. All classes must be available on the classpath when a test suite is executed.

3 Test fixtures

A test fixture is a set of resources that must be in place in order to run a test and verify the outcome. A fixture might include items such as metadata about the test subject, schemas used to validate response messages, input data, or specialized client components. Test fixtures can be created at multiple levels depending on how widely they should be shared. A class fixture is shared by all test methods defined in the class (or a subclass). A suite fixture contains items that are broadly accessible.

In the TestNG framework the ITestContext interface represents a high-level test fixture that can be augmented with user-defined attributes (of any type) that are set or retrieved as needed. One common testing scenario involves compiling an XML Schema resource using the JAXP Validation API and then storing the resulting thread-safe Schema object as a test suite (ISuite) attribute that can be readily accessed by test methods.

A test suite generated using the Maven archetype includes the org.opengis.cite.${ets-code}.SuiteFixtureListener class. The processSuiteParameters method demonstrates how to parse a test run input argument and store the resulting DOM Document object as a suite attribute (Listing 6).

Listing 6: Assembling a test suite fixture

ISuite suite;  // injected by TestNG
Map<String, String> params = suite.getXmlSuite().getParameters();
String iutParam = params.get(TestRunArg.IUT.toString());    
URI iutRef = URI.create(iutParam.trim());
Document iutDoc = URIUtils.parseURI(iutRef);
suite.setAttribute(SuiteAttribute.TEST_SUBJECT.getName(), iutDoc);

Note that in most cases the SuiteFixtureListener class will need to be modified in order to accommodate particular testing requirements. For example, if the main test input is not an XML resource it would be more appropriate to store the content of the resource in a local file or database for the duration of the test run.

4 Test listeners

Several listener interfaces are provided by the TestNG framework in order to modify or extend default behaviors. The ISuiteListener and ITestListener interfaces are of particular interest. The former includes methods that are invoked before and after a test suite is executed; the latter declares several callback methods pertaining to the life cycles of test classes and test methods.

A test suite generated using the Maven archetype contains several predefined listeners referenced in the definition file (see Listing 4); these listeners are summarized in Table

  1. They are all defined in the root package, except for PrimarySuiteListener which is provided by the teamengine-spi module.
Table 1: Predefined listeners
Name Purpose
TestRunListener (IExecutionListener) A listener that is invoked before and after a test run; it is typically used to configure components of the test environment for the duration of the entire test run.
PrimarySuiteListener (ISuiteListener) A listener provided by the teamengine-spi module, it adds the test run arguments to the collection of suite-level parameters. Since this listener will be called first, the parameters it sets will be available to all subsequent listeners.
SuiteFixtureListener (ISuiteListener) A listener that performs various initialization and clean-up tasks, such as: processing input arguments, compiling application schemas, and deleting any temporary files created during a test run.
TestFailureListener (ITestListener) A listener that augments a test result with diagnostic information in the event that a test method failed; this information will appear in the XML report when the test run is completed.

The predefined listeners may be modified if desired, and test developers can introduce additional listeners that perform various pre- and post-processing tasks or modify TestNG behavior. See the TestNG documentation for more information about the listener interfaces.

5 Test methods

In general, an abstract test case (ATC) gives rise to one or more test methods that realize it. A test method bears the @Test annotation, which is automatically detected by the test runner (SuiteRunner). In general, a test method includes at least one assertion in order to verify the expected outcome: the content of a response message, the state of the test subject, and so on. Listing 7 displays a test method that validates an XML resource against the RELAX NG grammar for Atom feeds.

Listing 7: Sample test method

 * Verify that the entity is a valid Atom feed (RFC 4287).
@Test(description = "ATC 1-3")
public void validAtomFeed() throws SAXException, IOException {
  URL schemaRef = getClass().getResource(
  RelaxNGValidator rngValidator = new RelaxNGValidator(schemaRef);
  rngValidator.validate(new DOMSource(testSubject));
  ValidationErrorHandler err = rngValidator.getErrorHandler();
        err.getErrorCount(), err.toString()));

Note that the @Test annotation in Listing 7 contains a description attribute; this refers to the test requirement(s) or abstract test case that form the test basis. The Javadoc comments for the method should provide more information about the expected result.

Test methods may accept parameters, which is a very useful capability in some circumstances. For example, when testing a web service a particular test may apply to every supported protocol binding listed in the service description. Instead of implementing one test for each binding, a single test with a parameter that identifies a specific binding will suffice. There are two main mechanisms for passing parameters:

  • specify simple values in the test suite definition (testng.xml)
  • supply arbitrary values—even Java objects—with data providers

While TestNG does provide a basic assertion facility, many test suites benefit from the use of custom assertions. The ETSAssert class in the root package is provided for this purpose, and test developers are free to add more as needed.

Informative error messages greatly aid the diagnosis of test failures. The test method shown in Listing 7 builds an assertion error message using a format string that includes several arguments supplying details and contextual information. The ErrorMessageKeys class in the root package defines keys that identify format strings in locale-specific resource bundles. For example, the ErrorMessageKeys.NOT_SCHEMA_VALID key value is “NotSchemaValid”; this corresponds to an entry in the properties file at src/main/resources/org/opengis/cite/${ets-code}/

NotSchemaValid = {0} schema validation error(s) detected.\n {1}

Test developers are strongly encouraged to follow this practice. As an additional benefit, error messages can be provided in multiple languages using locale-specific data. This is primarily accomplished by creating a new properties file that contains the translated values (, for example). For more information, see the Java internationalization tutorial.

A test suite can make use of third-party libraries as needed; these dependencies are explicitly identified in the project's POM file. The utility libraries listed in Table 2 may also be of interest if conformance testing calls for more specialized assertion checking. The source code can be obtained from GitHub, and the release artifacts are available from the Maven Central repository.

Table 2: OGC/CITE utility libraries
Library Description
schema-utils Provides support for validating XML representations using the following standard schema languages: W3C XML Schema 1.0, Schematron (ISO/IEC 19757-3:2006), and RELAX NG (ISO/IEC 19757-2:2008).
geomatics-geotk Provides support for processing spatial data and associated metadata using various Geotk modules.

In order to provide some assurance that a test suite is implemented correctly it is necessary to develop unit tests that verify the conformance test methods. The JUnit framework is used for this purpose. Several sample unit tests are can be found in the src/test/java directory.

Some conformance tests may use quite a few objects in the course of accessing a fixture, interacting with the IUT, or verifying a result. When it is desirable to mock or stub other objects in a unit test, the Mockito framework can be very useful.

6 Test preconditions

A test, conformance class, or even an entire test suite may be subject to various preconditions that must be satisfied before it can be executed. For example, a web service must be available before a test run is initiated. Tests covering optional capabilities are generally not run if they are not implemented. If any precondition is not met, the affected tests are assigned a “SKIP” result.

TestNG provides several annotations for configuration methods that check preconditions:

  • @BeforeSuite: The method will be run before any test methods in the suite are run.
  • @BeforeTest: The method will be run before any test methods in the affiliated <test> set are run (usually applied to conformance classes).
  • @BeforeClass: The method will be run before any test method defined in the current class is invoked.

As a convenience, a test suite generated with the Maven archetype contains a SuitePreconditions class wherein BeforeSuite methods can be defined. Be aware that if a class containing any configuration methods is not already included in the test suite definition, it must be added so the test runner will find it.

7 Further resources


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