fix: support error messages in subscription tests

Author: BlasiusSecundus

graphql-spring-boot-test/src/main/java/com/graphql/spring/boot/test/GraphQLTestSubscription.java

@@ -382,15 +382,18 @@ public void onMessage(final String message) {
             try {
                 log.debug("Received message from web socket: {}", message);
                 final JsonNode jsonNode = objectMapper.readTree(message);
-                final JsonNode type = jsonNode.get("type");
-                if (type.asText().equals("connection_ack")) {
+                final JsonNode typeNode = jsonNode.get("type");
+                assertThat(typeNode.isNull()).as("GraphQL messages should have a type field.").isFalse();
+                final String type = typeNode.asText();
+                if (type.equals("connection_ack")) {
                     acknowledged = true;
                     log.debug("WebSocket connection acknowledged by the GraphQL Server.");
-                } else if (type.asText().equals("data")) {
-                    final JsonNode data = jsonNode.get("payload");
-                    assertThat(data).as("Data message must have a payload.").isNotNull();
-                    final GraphQLResponse graphQLResponse
-                        = new GraphQLResponse(ResponseEntity.ok(objectMapper.writeValueAsString(data)), objectMapper);
+                } else if (type.equals("data") || type.equals("error")) {
+                    final JsonNode payload = jsonNode.get("payload");
+                    assertThat(payload).as("Data/error messages must have a payload.").isNotNull();
+                    final String payloadString = objectMapper.writeValueAsString(payload);
+                    final GraphQLResponse graphQLResponse = new GraphQLResponse(ResponseEntity.ok(payloadString),
+                        objectMapper);
                     synchronized (responses) {
                         responses.add(graphQLResponse);
                     }

graphql-spring-boot-test/src/test/java/com/graphql/spring/boot/test/GraphQLTestSubscriptionErrorTest.java

@@ -0,0 +1,20 @@
+package com.graphql.spring.boot.test;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@DisplayName("Test error message handling.")
+public class GraphQLTestSubscriptionErrorTest extends GraphQLTestSubscriptionTestBase {
+
+    @Test
+    @DisplayName("Should handle error messages.")
+    void shouldHandleErrorMessages() {
+        // WHEN
+        final GraphQLResponse graphQLResponse = graphQLTestSubscription.start(SUBSCRIPTION_THAT_THROWS_EXCEPTION)
+            .awaitAndGetNextResponse(TIMEOUT);
+        // THEN
+        assertThat(graphQLResponse.get("$.errors[0].message")).isNotBlank();
+    }
+}

graphql-spring-boot-test/src/test/java/com/graphql/spring/boot/test/GraphQLTestSubscriptionTestBase.java

@@ -17,6 +17,8 @@ public class GraphQLTestSubscriptionTestBase {
         = "subscription-with-init-payload-resource.graphql";
     protected static final String SUBSCRIPTION_THAT_TIMES_OUT_RESOURCE
         = "subscription-that-times-out-resource.graphql";
+    protected static final String SUBSCRIPTION_THAT_THROWS_EXCEPTION
+        = "subscription-that-throws-exception-resource.graphql";
     protected static final String DATA_TIMER_FIELD = "$.data.timer";
     protected static final String DATA_SUBSCRIPTION_WITH_PARAMETER_FIELD = "$.data.subscriptionWithParameter";
     protected static final String DATA_SUBSCRIPTION_WITH_INIT_PAYLOAD_FIELD = "$.data.subscriptionWithInitPayload";

graphql-spring-boot-test/src/test/java/com/graphql/spring/boot/test/beans/TestSubscriptions.java

@@ -29,4 +29,8 @@ public Flowable<String> subscriptionWithInitPayload() {
     public Flowable<Long> subscriptionThatTimesOut() {
         return Flowable.interval(20000, 20000, TimeUnit.MILLISECONDS);
     }
+
+    public Flowable<Boolean> subscriptionThatThrowsException() {
+        throw new RuntimeException("Test exception.");
+    }
 }

graphql-spring-boot-test/src/test/resources/subscription-that-throws-exception-resource.graphql

@@ -0,0 +1,3 @@
+subscription {
+    subscriptionThatThrowsException
+}

graphql-spring-boot-test/src/test/resources/test-schema.graphqls

@@ -5,6 +5,7 @@ type Subscription {
     subscriptionWithParameter(param: String!): String!
     subscriptionWithInitPayload: String!
     subscriptionThatTimesOut: Long!
+    subscriptionThatThrowsException: Boolean!
 }
 
 type Query {