junit-team/junit5 · error · UnsupportedOperationException

Please implement provideArguments(ParameterDeclarations, Ext

Error message

Please implement provideArguments(ParameterDeclarations, ExtensionContext) instead.

What it means

Thrown by the deprecated default provideArguments(ExtensionContext) in the ArgumentsProvider interface (UnsupportedOperationException). It is reached when a custom ArgumentsProvider overrides neither the current 2-arg nor the legacy 1-arg method. Normally the 2-arg default catches this and rewraps it (see error 63), so end users usually see 63 instead.

Source

Thrown at junit-jupiter-params/src/main/java/org/junit/jupiter/params/provider/ArgumentsProvider.java:61

 * @see org.junit.jupiter.params.support.AnnotationConsumer
 */
@API(status = STABLE, since = "5.7")
public interface ArgumentsProvider {

	/**
	 * Provide a {@link Stream} of {@link Arguments} to be passed to a
	 * {@code @ParameterizedTest} method.
	 *
	 * @param context the current extension context; never {@code null}
	 * @return a stream of arguments; never {@code null}
	 * @deprecated Please implement
	 * {@link #provideArguments(ParameterDeclarations, ExtensionContext)} instead.
	 */
	@Deprecated(since = "5.13")
	@API(status = DEPRECATED, since = "5.13")
	default Stream<? extends Arguments> provideArguments(@SuppressWarnings("unused") ExtensionContext context)
			throws Exception {
		throw new UnsupportedOperationException(
			"Please implement provideArguments(ParameterDeclarations, ExtensionContext) instead.");
	}

	/**
	 * Provide a {@link Stream} of {@link Arguments} to be passed to a
	 * {@code @ParameterizedClass} or {@code @ParameterizedTest}.
	 *
	 * @param parameters the parameter declarations for the parameterized
	 * class or test; never {@code null}
	 * @param context the current extension context; never {@code null}
	 * @return a stream of arguments; never {@code null}
	 * @since 5.13
	 */
	@API(status = MAINTAINED, since = "6.0.2")
	default Stream<? extends Arguments> provideArguments(ParameterDeclarations parameters, ExtensionContext context)
			throws Exception {
		try {
			return provideArguments(context);

View on GitHub (pinned to 956246301e)

Solutions

Implement `Stream<? extends Arguments> provideArguments(ParameterDeclarations parameters, ExtensionContext context)` in the provider.
If extending AnnotationBasedArgumentsProvider, override the 3-arg variant instead.
Upgrade or pin JUnit to match the provider's expected contract.

Example fix

// before
class MyProvider implements ArgumentsProvider { }

// after
class MyProvider implements ArgumentsProvider {
    @Override
    public Stream<? extends Arguments> provideArguments(
            ParameterDeclarations parameters, ExtensionContext context) {
        return Stream.of(Arguments.of(1, 2));
    }
}

Defensive patterns

Strategy: validation

Validate before calling

// Assert a custom ArgumentsProvider implements the current 2-arg contract.
Class<? extends ArgumentsProvider> provider = MyProvider.class;
boolean ok = Arrays.stream(provider.getMethods())
    .anyMatch(m -> m.getName().equals("provideArguments")
        && m.getParameterCount() == 2
        && !m.isDefault());
if (!ok) {
    throw new IllegalStateException(provider.getName()
        + " must override provideArguments(ParameterDeclarations, ExtensionContext)");
}

Try / catch

try {
    // execute the parameterized test
} catch (UnsupportedOperationException e) {
    if (e.getMessage().contains("implement provideArguments")) {
        // add the 2-arg override to the provider
    } else throw e;
}

Prevention

Always override provideArguments(ParameterDeclarations, ExtensionContext) in custom providers.
Use @Override so the compiler rejects missing/incorrect signatures.
Keep providers' JUnit version aligned with the runtime version.

When it happens

Trigger: A custom ArgumentsProvider registered via @ArgumentsSource that provides no implementation of provideArguments; the 2-arg default delegates to the 1-arg default which throws UnsupportedOperationException.

Common situations: Newly created provider with an empty body; IDE auto-generated stubs that did not fill the method; upgrade from a pre-5.13 JUnit where the 1-arg method was the interface contract.

Related errors

AI-assisted analysis of junit-team/junit5@956246301e (2026-08-04). Data as JSON: /data/errors/994e7429add32343.json. Report an issue: GitHub.