junit-team/junit5 · error · ExtensionConfigurationException

When the display name pattern for a @%s contains %s, the arg

Error message

When the display name pattern for a @%s contains %s, the arguments must be supplied as an ArgumentSet.

What it means

Thrown by ArgumentSetNameFormatter.append() when the display name pattern contains {argumentSetName} but the current invocation's arguments were not created via Arguments.argumentSet(name, ...). The {argumentSetName} placeholder requires a named argument set; regular sources like @ValueSource, @CsvSource, or @MethodSource do not assign names to argument sets.

Source

Thrown at junit-jupiter-params/src/main/java/org/junit/jupiter/params/ParameterizedInvocationNameFormatter.java:231

	@FunctionalInterface
	private interface PartialFormatter {

		PartialFormatter INDEX = (context, result) -> result.append(context.invocationIndex);

		void append(ArgumentsContext context, StringBuffer result);

	}

	private record ArgumentSetNameFormatter(String annotationName) implements PartialFormatter {

		@Override
		public void append(ArgumentsContext context, StringBuffer result) {
			if (context.argumentSetName != null) {
				result.append(context.argumentSetName);
				return;
			}
			throw new ExtensionConfigurationException(
				"When the display name pattern for a @%s contains %s, the arguments must be supplied as an ArgumentSet.".formatted(
					this.annotationName, ARGUMENT_SET_NAME_PLACEHOLDER));
		}
	}

	private static class MessageFormatPartialFormatter implements PartialFormatter {

		@SuppressWarnings("UnnecessaryUnicodeEscape")
		private static final char ELLIPSIS = '\u2026';

		private final MessageFormat messageFormat;
		private final int argumentMaxLength;
		private final boolean generateNameValuePairs;
		private final @Nullable ResolverFacade resolverFacade;

		MessageFormatPartialFormatter(String pattern, int argumentMaxLength) {
			this(pattern, argumentMaxLength, false, null);
		}

View on GitHub (pinned to 956246301e)

Solutions

Use {argumentSetNameOrArgumentsWithNames} instead of {argumentSetName} — it gracefully falls back to showing argument names when no set name exists
If {argumentSetName} is required, change the arguments source to produce Arguments.argumentSet("myName", val1, val2) instead of Arguments.of(val1, val2)
Use a simpler pattern like {index} or {arguments} if named sets are not needed

Example fix

// before
@ParameterizedTest(name = "{argumentSetName}")
@MethodSource("provider")
void test(int x) { }
static Stream<Arguments> provider() {
    return Stream.of(Arguments.of(1)); // no name
}

// after (use argumentSet)
@ParameterizedTest(name = "{argumentSetName}")
@MethodSource("provider")
void test(int x) { }
static Stream<Arguments> provider() {
    return Stream.of(Arguments.argumentSet("positive", 1));
}

Defensive patterns

Strategy: validation

Validate before calling

// Use the safe alternative placeholder that falls back gracefully:
@ParameterizedTest(name = ParameterizedInvocationConstants.ARGUMENT_SET_NAME_OR_ARGUMENTS_WITH_NAMES_PLACEHOLDER)
// Or, if {argumentSetName} is used, ensure Arguments.argumentSet() is called:
static Stream<Arguments> provider() {
    return Stream.of(Arguments.argumentSet("positive", 1, 2));
}

Prevention

Prefer {argumentSetNameOrArgumentsWithNames} over {argumentSetName} — it falls back to {argumentsWithNames} when no set name exists
Only use {argumentSetName} when all argument sets are created via Arguments.argumentSet(name, ...)
Do not mix Arguments.of(...) and Arguments.argumentSet(...) in the same source if using {argumentSetName}

When it happens

Trigger: Using name = "{argumentSetName}" (or explicitly referencing ARGUMENT_SET_NAME_PLACEHOLDER) on a @ParameterizedTest or @ParameterizedClass where arguments come from a source that does not use Arguments.argumentSet() — e.g., @ValueSource, @CsvSource, or a @MethodSource returning Arguments.of(...) instead of Arguments.argumentSet(...).

Common situations: Copying a display name pattern that was designed for named argument sets to a test that uses plain argument sources. Upgrading and adopting {argumentSetName} without switching the arguments source to use Arguments.argumentSet(). Note: {argumentSetNameOrArgumentsWithNames} is a safe alternative that falls back to {argumentsWithNames} when no name is set.

Related errors

AI-assisted analysis of junit-team/junit5@956246301e (2026-08-04). Data as JSON: /data/errors/0f90e2c061d579e9.json. Report an issue: GitHub.