junit-team/junit5 · error · JUnitException

Invalid ' ' set via the ' ' configuration parameter.

Error message

Invalid %s '%s' set via the '%s' configuration parameter.

What it means

JUnitException from EnumConfigurationParameterConverter.convert, thrown when a configuration parameter that should map to an enum constant cannot be parsed. The converter upper-cases and strips the supplied value, then calls Enum.valueOf; if that throws (no such constant), the whole thing is wrapped as a JUnitException naming the enum display name, the offending value, and the config key.

Solutions

  1. Check the enum's actual constant names in the JUnit version you target and use the exact name (case-insensitive after normalization).
  2. Strip surrounding quotes/whitespace from the value in junit.properties / -D argument.
  3. If migrating versions, look up the changelog for renamed/removed constants and update accordingly.
  4. The exception message echoes the normalized value it tried — use it to spot typos.

Example fix

// before (junit.properties)
junit.jupiter.testclass.order.default = classname
// after
junit.jupiter.testclass.order.default = ClassName
Defensive patterns

Strategy: validation

Validate before calling

String raw = configParams.get(key).orElse(null);
if (raw != null) {
    String norm = raw.strip().toUpperCase(Locale.ROOT);
    Set<String> valid = Arrays.stream(enumType.getEnumConstants())
            .map(Enum::name).collect(toSet());
    if (!valid.contains(norm)) { /* invalid config value */ }
}

Type guard

static <E extends Enum<E>> boolean isValidEnumValue(Class<E> enumType, String raw) {
    try {
        Enum.valueOf(enumType, raw.strip().toUpperCase(Locale.ROOT));
        return true;
    } catch (IllegalArgumentException e) {
        return false;
    }
}

Try / catch

try {
    Optional<E> v = converter.get(configParams, key);
} catch (JUnitException e) {
    // message names the bad value and key; correct junit.properties / -D flag
}

Prevention

When it happens

Trigger: Setting a JUnit configuration parameter (e.g. junit.jupiter.execution.parallel.enabled, junit.jupiter.testclass.order.default, junit.jupiter.displayname.generator.default) to a value that is not a valid constant of the expected enum (e.g. typo, wrong case even after normalization, or a constant removed in a newer version).

Common situations: Typos in junit.properties or -D flags; copying a value from an older JUnit version whose enum constant was renamed/removed; locale-specific casing surprises (mitigated by Locale.ROOT upper-casing); trailing whitespace or quotes around the value.

Related errors

AI-assisted analysis of junit-team/junit5@f070c699a0 (2026-08-11). Data as JSON: /api/errors/13ed00353d406d33. Report an issue: GitHub.

Appendix: source

Thrown at junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/config/EnumConfigurationParameterConverter.java:61

		return configParams.get(key) //
				.map(value -> convert(key, value));
	}

	public Optional<E> get(ExtensionContext extensionContext, String key) {
		return extensionContext.getConfigurationParameter(key, value -> convert(key, value));
	}

	private E convert(String key, String value) {
		String constantName = null;
		try {
			constantName = value.strip().toUpperCase(Locale.ROOT);
			E result = Enum.valueOf(enumType, constantName);
			logger.config(() -> "Using %s '%s' set via the '%s' configuration parameter.".formatted(enumDisplayName,
				result, key));
			return result;
		}
		catch (Exception ex) {
			throw new JUnitException("Invalid %s '%s' set via the '%s' configuration parameter.".formatted(
				enumDisplayName, constantName, key));
		}
	}

}

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