private static CircuitBreakerRuleWithContent<HttpResponse> ruleWithResponse() {
        return (ctx, response, cause) -> UnmodifiableFuture.completedFuture(
                cause == null ? CircuitBreakerDecision.failure() : CircuitBreakerDecision.success());
    }
A rule with content that returns failure when am exception is thrown, and success otherwise.
core/src/test/java/com/linecorp/armeria/client/circuitbreaker/CircuitBreakerClientTest.java