fixup! Kraken: Handle Errors field in futures response

exchanges/kraken/kraken_test.go

@@ -2394,3 +2394,20 @@ func TestErrorResponse(t *testing.T) {
 		})
 	}
 }
+
+func TestGetFuturesErr(t *testing.T) {
+	t.Parallel()
+
+	assert.ErrorContains(t, getFuturesErr(json.RawMessage(`unparsable rubbish`)), "invalid character", "Bad JSON should error correctly")
+	assert.NoError(t, getFuturesErr(json.RawMessage(`{"candles":[]}`)), "JSON with no Result should not error")
+	assert.NoError(t, getFuturesErr(json.RawMessage(`{"Result":"4 goats"}`)), "JSON with non-error Result should not error")
+	assert.ErrorIs(t, getFuturesErr(json.RawMessage(`{"Result":"error"}`)), common.ErrUnknownError, "JSON with error Result should error correctly")
+	assert.ErrorContains(t, getFuturesErr(json.RawMessage(`{"Result":"error", "error": "1 goat"}`)), "1 goat", "JSON with an error should error correctly")
+	err := getFuturesErr(json.RawMessage(`{"Result":"error", "errors": ["2 goats", "3 goats"]}`))
+	assert.ErrorContains(t, err, "2 goat", "JSON with errors should error correctly")
+	assert.ErrorContains(t, err, "3 goat", "JSON with errors should error correctly")
+	err = getFuturesErr(json.RawMessage(`{"Result":"error", "error": "too many goats", "errors": ["2 goats", "3 goats"]}`))
+	assert.ErrorContains(t, err, "2 goat", "JSON with both error and errors should error correctly")
+	assert.ErrorContains(t, err, "3 goat", "JSON with both error and errors should error correctly")
+	assert.ErrorContains(t, err, "too many goat", "JSON both error and with errors should error correctly")
+}