junit-team/junit5 · error · JUnitException

The display name pattern defined for the parameterized test

Error message

The display name pattern defined for the parameterized test is invalid. See nested exception for further details.

What it means

Thrown by the ParameterizedInvocationNameFormatter constructor when parsing the display name pattern (the 'name' attribute of @ParameterizedTest or @ParameterizedClass) throws an exception. The pattern is parsed into PartialFormatter segments that may contain java.text.MessageFormat sub-patterns for literal text containing curly braces. Invalid MessageFormat syntax in these segments triggers the nested exception.

Source

Thrown at junit-jupiter-params/src/main/java/org/junit/jupiter/params/ParameterizedInvocationNameFormatter.java:94

				.orElse(512);
		Preconditions.condition(argumentMaxLength > 0,
			() -> ARGUMENT_MAX_LENGTH_KEY + " must be a positive number: " + argumentMaxLength);

		return new ParameterizedInvocationNameFormatter(pattern, extensionContext.getDisplayName(), declarationContext,
			argumentMaxLength);
	}

	private final PartialFormatter[] partialFormatters;

	ParameterizedInvocationNameFormatter(String pattern, String displayName,
			ParameterizedDeclarationContext<?> declarationContext, int argumentMaxLength) {
		try {
			this.partialFormatters = parse(pattern, displayName, declarationContext, argumentMaxLength);
		}
		catch (Exception ex) {
			String message = "The display name pattern defined for the parameterized test is invalid. "
					+ "See nested exception for further details.";
			throw new JUnitException(message, ex);
		}
	}

	String format(int invocationIndex, EvaluatedArgumentSet arguments, boolean quoteTextArguments) {
		try {
			return formatSafely(invocationIndex, arguments, quoteTextArguments);
		}
		catch (Exception ex) {
			String message = "Failed to format display name for parameterized test. "
					+ "See nested exception for further details.";
			throw new JUnitException(message, ex);
		}
	}

	@SuppressWarnings("JdkObsolete")
	private String formatSafely(int invocationIndex, EvaluatedArgumentSet arguments, boolean quoteTextArguments) {
		ArgumentsContext context = new ArgumentsContext(invocationIndex, arguments.getConsumedArguments(),
			arguments.getName(), quoteTextArguments);

View on GitHub (pinned to 956246301e)

Solutions

1. Use the documented JUnit placeholders: {index}, {displayName}, {arguments}, {argumentsWithNames}, {argumentSetName}, {0}, {1}, etc.
2. If you need literal curly braces in the display name, escape them as MessageFormat requires: use ''{'' and ''}'' (single-quote escapes)
3. Simplify the pattern to isolate which segment is malformed, then re-add complexity
4. Check the nested exception in the stack trace for the exact MessageFormat parse error

Example fix

// before
@ParameterizedTest(name = "test { for {0}")
void test(int x) { }

// after (escape literal braces or remove them)
@ParameterizedTest(name = "test for {0}")
void test(int x) { }

// Validate the display name pattern before applying it:
static void validateDisplayNamePattern(String pattern) {
    try {
        // Test that any literal brace segments parse as MessageFormat
        if (pattern.contains("{" )) {
            new MessageFormat(pattern.replaceAll("\\{index}|\\{arguments}|\\{displayName", ""));
        }
    } catch (Exception e) {
        throw new IllegalArgumentException("Invalid display name pattern: " + pattern, e);
    }
}
// Simpler: stick to documented placeholders and avoid raw curly braces

When it happens

Trigger: Setting name = "{0} test" or name = "test {" on @ParameterizedTest(name=...) or @ParameterizedClass(name=...) where the curly-brace segment is not a valid MessageFormat pattern. For example, an unmatched single brace '{' or a malformed format choice/type specifier.

Common situations: Using a display name pattern that contains literal curly braces for formatting but has syntax errors (e.g., '{' without closing '}', '{0,date}' with an unsupported format type). Confusing JUnit placeholders like {index} (which are fine) with MessageFormat patterns like {0}.

Related errors

• Failed to format display name for parameterized test. See ne
• When the display name pattern for a @%s contains %s, the arg
• Configuration error: You must configure at least one set of
• Unsupported argument count validation mode: <mode>
• Constructor injection is not supported for @ParameterizedCla

AI-assisted analysis of junit-team/junit5@956246301e (2026-08-04). Data as JSON: /data/errors/6982ddc59a81cbf7.json. Report an issue: GitHub.