karatelabs/karate · error · RuntimeException

configure() needs two arguments: key and value

Error message

configure() needs two arguments: key and value

What it means

karate.configure(key, value) sets a configuration option at runtime and requires exactly the key and value arguments. Karate throws this when fewer than two arguments are supplied, since a key alone (or no arguments) cannot configure anything.

Solutions

  1. Pass both key and value: karate.configure('headers', {Authorization: 'Basic ...'}).
  2. If the value is an object/function (e.g. retry config), supply it as the second argument, not merged into the key.
  3. Check spelling and arity of the call; karate.configure never accepts a single options map.

Example fix

// before
karate.configure('retry');

// after
karate.configure('retry', { count: 3, interval: 1000 });
Defensive patterns

Strategy: validation

Validate before calling

if (key == null || value === undefined) { throw new Error('configure needs key and value'); } karate.configure(key, value);

Type guard

function canConfigure(key, value) { return typeof key === 'string' && key.length > 0 && value !== undefined; }

Try / catch

try { karate.configure(key, value); } catch (e) { if (String(e.message).includes('needs two arguments')) { karate.log('configure arity error for key: ' + key); } throw e; }

Prevention

When it happens

Trigger: `karate.configure('retry')` or `karate.configure()` called from JS with one or zero arguments.

Common situations: Typos in configure calls; porting Java-side configure(key, value) to JS incorrectly; assuming a single object argument form is supported (it is not — key and value must be separate).

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/18427adf1d25eceb. Report an issue: GitHub.

Appendix: source

Thrown at karate-core/src/main/java/io/karatelabs/core/KarateJsBase.java:422

            if (rt == null) {
                throw new RuntimeException("karate.callSingle() is not available in this context");
            }
            if (args.length == 0) {
                throw new RuntimeException("karate.callSingle() requires at least one argument (path)");
            }
            String path = args[0].toString();
            Object arg = args.length > 1 ? args[1] : null;
            return rt.executeCallSingle(path, arg);
        };
    }

    /**
     * karate.configure() - Apply configuration from JavaScript.
     */
    JavaInvokable configure() {
        return args -> {
            if (args.length < 2) {
                throw new RuntimeException("configure() needs two arguments: key and value");
            }
            String key = args[0].toString();
            Object value = args[1];
            ScenarioRuntime rt = getRuntime();
            if (rt != null) {
                rt.configure(key, value);
            }
            return null;
        };
    }

    /**
     * Returns system properties available via karate.properties['key'].
     */
    Map<String, String> getProperties() {
        Suite suite = getSuite();
        if (suite != null) {
            return suite.getSystemProperties();

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