    @Test
    public void depth_error() throws Exception {

        when(mockGuestApi.call(anyString()))
                .thenReturn(JSON_PARSER.parse("{\"success\":0," +
                        " \"error\":\"Invalid pair name: btc_us\"}").getAsJsonObject());

        CallResult<Depth> depthCallResult = testable.depth("BTC/US");
        assertFalse(depthCallResult.isSuccess());
        assertNotNull(depthCallResult.getError());
        assertNull(depthCallResult.getPayload());
    }