karatelabs/karate · warning

Failed to write JUnit XML for

Error message

Failed to write JUnit XML for {}: {}

What it means

JunitXmlWriter.writeFeature() converts a FeatureResult to XML and writes it as <packageQualifiedName>.xml in the output directory. Any exception in conversion or writing is logged with the feature's display name; the test run continues without that XML report.

Solutions

1. Ensure outputDir exists and is writable before calling writeFeature
2. Check the derived fileName (packageQualifiedName) for illegal characters or collisions
3. Enable debug logging ('JUnit XML written' vs the warning) to isolate the failing feature
4. Inspect the FeatureResult content for data that breaks conversion and upgrade Karate if it is a serializer bug

if (!Files.isWritable(outputDir))
    throw new IllegalStateException("output dir not writable: " + outputDir);
String name = result.getFeature().getResource().getPackageQualifiedName() + ".xml";
if (!name.matches("[A-Za-z0-9._-]+")) logger.warn("suspicious xml file name: {}", name);

try {
    Files.writeString(outputDir.resolve(fileName), featureToXml(result));
} catch (Exception e) {
    logger.warn("Failed to write JUnit XML for {}: {}", result.getDisplayName(), e.getMessage(), e);
}

When it happens

Trigger: Exception from featureToXml(result) or Files.writeString(xmlPath, xml) — unwritable/missing output directory, or a FeatureResult whose content breaks XML generation.

Common situations: Legacy callers writing JUnit XML outside the listener flow; outputDir cleaned concurrently; features with names producing colliding or invalid XML file names; serialization bugs on unusual result data.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• Failed to write JUnit XML for
• Failed to copy static resources
• Failed to write HTML report
• Failed to externalize embeds
• Failed to copy ext assets for

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/1292b7fafcdc6e1d. Report an issue: GitHub.

Appendix: source

Thrown at karate-core/src/main/java/io/karatelabs/output/JunitXmlWriter.java:117

            Files.writeString(outputDir.resolve(fileName), content);
        } catch (Exception e) {
            logger.warn("Failed to write xml for {}: {}", fileName, e.getMessage());
        }
    }

    public static void writeFeature(FeatureResult result, Path outputDir) {
        try {
            if (!Files.exists(outputDir)) {
                Files.createDirectories(outputDir);
            }

            String fileName = result.getFeature().getResource().getPackageQualifiedName() + ".xml";
            Path xmlPath = outputDir.resolve(fileName);
            String xml = featureToXml(result);
            Files.writeString(xmlPath, xml);
            logger.debug("JUnit XML written: {}", xmlPath);
        } catch (Exception e) {
            logger.warn("Failed to write JUnit XML for {}: {}", result.getDisplayName(), e.getMessage());
        }
    }

    /**
     * Convert a single feature result to JUnit XML string.
     *
     * @param result the feature result
     * @return XML string
     */
    public static String featureToXml(FeatureResult result) {
        DecimalFormat formatter = (DecimalFormat) NumberFormat.getNumberInstance(Locale.US);
        formatter.applyPattern("0.######");

        String packageQualifiedName = result.getFeature().getResource().getPackageQualifiedName();

        StringBuilder xml = new StringBuilder();

        // Root testsuite element (single feature)

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