JUnit 5 Parameterized test @ArgumentsSource parameters not loading

Question

I have created below JUnit5 parameterized test with ArgumentsSource for loading arguments for the test:

public class DemoModelValidationTest {

public ParamsProvider paramsProvider;

public DemoModelValidationTest () {
    try {
         paramsProvider = new ParamsProvider();
    }
    catch (Exception iaex) {
        
    }
}
    
@ParameterizedTest
@ArgumentsSource(ParamsProvider.class)
void testAllConfigurations(int configIndex, String a) throws Exception {
  paramsProvider.executeSimulation(configIndex);
}  

}

and the ParamsProvider class looks like below:

public class ParamsProvider implements ArgumentsProvider {
public static final String modelPath = System.getProperty("user.dir") + File.separator + "demoModels";

YAMLDeserializer deserializedYAML;
MetaModelToValidationModel converter;
ValidationRunner runner;
List<Configuration> configurationList;
List<Arguments> listOfArguments;

public ParamsProvider() throws Exception {
    configurationList = new ArrayList<>();
    listOfArguments = new LinkedList<>();
    deserializedYAML = new YAMLDeserializer(modelPath);
    deserializedYAML.load();

    converter = new MetaModelToValidationModel(deserializedYAML);
    runner = converter.convert();
    configurationList = runner.getConfigurations();

    for (int i = 0; i < configurationList.size(); i++) {
        listOfArguments.add(Arguments.of(i, configurationList.get(i).getName()));
    }
}

public void executeSimulation(int configListIndex) throws Exception {
    final Configuration config = runner.getConfigurations().get(configListIndex);
    runner.run(config);
    runner.getReporter().consolePrintReport();
}

@Override
public Stream<? extends Arguments> provideArguments(ExtensionContext context) {

    return listOfArguments.stream().map(Arguments::of);
    //      return Stream.of(Arguments.of(0, "Actuator Power"), Arguments.of(1, "Error Logging"));

}}

In the provideArguments() method, the commented out code is working fine, but the first line of code

listOfArguments.stream().map(Arguments::of)

is returning the following error:

org.junit.platform.commons.PreconditionViolationException: Configuration error: You must configure at least one set of arguments for this @ParameterizedTest

I am not sure whether I am having a casting problem for the stream in provideArguments() method, but I guess it somehow cannot map the elements of listOfArguments to the stream, which can finally take the form like below:

Stream.of(Arguments.of(0, "Actuator Power"), Arguments.of(1, "Error Logging"))

Am I missing a proper stream mapping of listOfArguments?

Answer 1

provideArguments(…) is called before your test is invoked.

Your ParamsProvider class is instantiated by JUnit. Whatever you’re doing in desiralizeAndCreateValidationRunnerInstance should be done in the ParamsProvider constructor.

Also you’re already wrapping the values fro deserialised configurations to Arguments and you’re double wrapping them in providesArguments.

Do this:

@Override
public Stream<? extends Arguments> provideArguments(ExtensionContext context) {

return listOfArguments.stream();

}}