Add serialization round-trip tests for event types

.gitignore

@@ -38,3 +38,4 @@ experimental/aws-lambda-java-profiler/integration_tests/helloworld/bin
 .vscode
 .kiro
 build
+mise.toml

aws-lambda-java-serialization/src/main/java/com/amazonaws/services/lambda/runtime/serialization/events/modules/DateModule.java

@@ -15,10 +15,17 @@
 import com.fasterxml.jackson.databind.module.SimpleModule;
 
 /**
- * The AWS API represents a date as a double, which specifies the fractional
- * number of seconds since the epoch. Java's Date, however, represents a date as
- * a long, which specifies the number of milliseconds since the epoch. This
- * class is used to translate between these two formats.
+ * The AWS API represents a date as a double (fractional seconds since epoch).
+ * Java's Date uses a long (milliseconds since epoch). This module translates
+ * between the two formats.
+ *
+ * <p>
+ * <b>Round-trip caveats:</b> The serializer always writes via
+ * {@link JsonGenerator#writeNumber(double)}, so integer epochs
+ * (e.g. {@code 1428537600}) round-trip as decimal ({@code 1.4285376E9}).
+ * Sub-millisecond precision is lost because {@link java.util.Date}
+ * has milliseconds precision.
+ * </p>
  * 
  * This class is copied from LambdaEventBridgeservice
  * com.amazon.aws.lambda.stream.ddb.DateModule

aws-lambda-java-tests/src/main/java/com/amazonaws/services/lambda/runtime/tests/JsonNodeUtils.java

@@ -0,0 +1,110 @@
+package com.amazonaws.services.lambda.runtime.tests;
+
+import com.amazonaws.lambda.thirdparty.com.fasterxml.jackson.databind.JsonNode;
+import com.amazonaws.lambda.thirdparty.com.fasterxml.jackson.databind.node.ObjectNode;
+import java.util.Iterator;
+import java.util.List;
+import java.util.TreeSet;
+import java.util.regex.Pattern;
+
+import org.joda.time.DateTime;
+
+/**
+ * Utility methods for working with shaded Jackson {@link JsonNode} trees.
+ *
+ * <p>
+ * Package-private — not part of the public API.
+ * </p>
+ */
+class JsonNodeUtils {
+
+    private static final Pattern ISO_DATE_REGEX = Pattern.compile("\\d{4}-\\d{2}-\\d{2}T.+");
+
+    private JsonNodeUtils() {
+    }
+
+    /**
+     * Recursively removes all fields whose value is {@code null} from the
+     * tree. This mirrors the serializer's {@code Include.NON_NULL} behaviour
+     * so that explicit nulls in the fixture don't cause false-positive diffs.
+     */
+    static JsonNode stripNulls(JsonNode node) {
+        if (node.isObject()) {
+            ObjectNode obj = (ObjectNode) node;
+            Iterator<String> fieldNames = obj.fieldNames();
+            while (fieldNames.hasNext()) {
+                String field = fieldNames.next();
+                if (obj.get(field).isNull()) {
+                    fieldNames.remove();
+                } else {
+                    stripNulls(obj.get(field));
+                }
+            }
+        } else if (node.isArray()) {
+            for (JsonNode element : node) {
+                stripNulls(element);
+            }
+        }
+        return node;
+    }
+
+    /**
+     * Recursively walks both trees and collects human-readable diff lines.
+     */
+    static void diffNodes(String path, JsonNode expected, JsonNode actual, List<String> diffs) {
+        if (expected.equals(actual))
+            return;
+
+        // Compares two datetime strings by parsed instant, because DateTimeModule
+        // normalizes the format on serialization (e.g. "+0000" → "Z", "Z" → ".000Z")
+        if (areSameDateTime(expected.textValue(), actual.textValue())) {
+            return;
+        }
+
+        if (expected.isObject() && actual.isObject()) {
+            TreeSet<String> allKeys = new TreeSet<>();
+            expected.fieldNames().forEachRemaining(allKeys::add);
+            actual.fieldNames().forEachRemaining(allKeys::add);
+            for (String key : allKeys) {
+                diffChild(path + "." + key, expected.get(key), actual.get(key), diffs);
+            }
+        } else if (expected.isArray() && actual.isArray()) {
+            for (int i = 0; i < Math.max(expected.size(), actual.size()); i++) {
+                diffChild(path + "[" + i + "]", expected.get(i), actual.get(i), diffs);
+            }
+        } else {
+            diffs.add("CHANGED " + path + " : " + summarize(expected) + " -> " + summarize(actual));
+        }
+    }
+
+    /**
+     * Compares two strings by parsed instant when both look like ISO-8601 dates,
+     * because DateTimeModule normalizes format on serialization
+     * (e.g. "+0000" → "Z", "Z" → ".000Z").
+     */
+    private static boolean areSameDateTime(String expected, String actual) {
+        if (expected == null || actual == null
+                || !ISO_DATE_REGEX.matcher(expected).matches()
+                || !ISO_DATE_REGEX.matcher(actual).matches()) {
+            return false;
+        }
+        return DateTime.parse(expected).equals(DateTime.parse(actual));
+    }
+
+    private static void diffChild(String path, JsonNode expected, JsonNode actual, List<String> diffs) {
+        if (expected == null)
+            diffs.add("ADDED   " + path + " = " + summarize(actual));
+        else if (actual == null)
+            diffs.add("MISSING " + path + " (was " + summarize(expected) + ")");
+        else
+            diffNodes(path, expected, actual, diffs);
+    }
+
+    private static String summarize(JsonNode node) {
+        if (node == null) {
+            return "<absent>";
+        }
+        String text = node.toString();
+        return text.length() > 80 ? text.substring(0, 77) + "..." : text;
+    }
+}

aws-lambda-java-tests/src/main/java/com/amazonaws/services/lambda/runtime/tests/LambdaEventAssert.java

@@ -0,0 +1,147 @@
+package com.amazonaws.services.lambda.runtime.tests;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.UncheckedIOException;
+import com.amazonaws.services.lambda.runtime.serialization.PojoSerializer;
+import com.amazonaws.services.lambda.runtime.serialization.events.LambdaEventSerializers;
+import com.amazonaws.lambda.thirdparty.com.fasterxml.jackson.databind.JsonNode;
+import com.amazonaws.lambda.thirdparty.com.fasterxml.jackson.databind.ObjectMapper;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Framework-agnostic assertion utilities for verifying Lambda event
+ * serialization.
+ *
+ * <p>
+ * When opentest4j is on the classpath (e.g. JUnit 5.x / JUnit Platform),
+ * assertion failures are reported as
+ * {@code org.opentest4j.AssertionFailedError}
+ * which enables rich diff support in IDEs. Otherwise, falls back to plain
+ * {@link AssertionError}.
+ * </p>
+ *
+ * <p>
+ * This class is intentionally package-private to support updates to 
+ * the aws-lambda-java-events and aws-lambda-java-serialization packages.
+ * Consider making it public if there's a real request for it.
+ * </p>
+ */
+class LambdaEventAssert {
+
+    private static final ObjectMapper MAPPER = new ObjectMapper();
+
+    /**
+     * Round-trip using the registered {@link LambdaEventSerializers} path
+     * (Jackson + mixins + DateModule + DateTimeModule + naming strategies).
+     *
+     * <p>
+     * The check performs two consecutive round-trips
+     * (JSON &rarr; POJO &rarr; JSON &rarr; POJO &rarr; JSON) and compares the
+     * original JSON tree against the final output tree. A single structural
+     * comparison catches both:
+     * </p>
+     * <ul>
+     * <li>Fields silently dropped during deserialization</li>
+     * <li>Non-idempotent serialization (output changes across round-trips)</li>
+     * </ul>
+     *
+     * @param fileName    classpath resource name (must end with {@code .json})
+     * @param targetClass the event class to deserialize into
+     * @throws AssertionError if the original and final JSON trees differ
+     */
+    public static <T> void assertSerializationRoundTrip(String fileName, Class<T> targetClass) {
+        PojoSerializer<T> serializer = LambdaEventSerializers.serializerFor(targetClass,
+                ClassLoader.getSystemClassLoader());
+
+        if (!fileName.endsWith(".json")) {
+            throw new IllegalArgumentException("File " + fileName + " must have json extension");
+        }
+
+        byte[] originalBytes;
+        try (InputStream stream = Thread.currentThread().getContextClassLoader().getResourceAsStream(fileName)) {
+            if (stream == null) {
+                throw new IllegalArgumentException("Could not load resource '" + fileName + "' from classpath");
+            }
+            originalBytes = toBytes(stream);
+        } catch (IOException e) {
+            throw new UncheckedIOException("Failed to read resource " + fileName, e);
+        }
+
+        // Two round-trips: original → POJO → JSON → POJO → JSON
+        // We are doing 2 passes so we can check instability problems
+        // like UnstablePojo in LambdaEventAssertTest
+        ByteArrayOutputStream firstOutput = roundTrip(new ByteArrayInputStream(originalBytes), serializer);
+        ByteArrayOutputStream secondOutput = roundTrip(
+                new ByteArrayInputStream(firstOutput.toByteArray()), serializer);
+
+        // Compare original tree against final tree.
+        // Strip explicit nulls from the original because the serializer is
+        // configured with Include.NON_NULL — null fields are intentionally
+        // omitted and that is not a data-loss bug.
+        try {
+            JsonNode originalTree = JsonNodeUtils.stripNulls(MAPPER.readTree(originalBytes));
+            JsonNode finalTree = MAPPER.readTree(secondOutput.toByteArray());
+
+            if (!originalTree.equals(finalTree)) {
+                List<String> diffs = new ArrayList<>();
+                JsonNodeUtils.diffNodes("", originalTree, finalTree, diffs);
+
+                if (!diffs.isEmpty()) {
+                    StringBuilder msg = new StringBuilder();
+                    msg.append("Serialization round-trip failure for ")
+                            .append(targetClass.getSimpleName())
+                            .append(" (").append(diffs.size()).append(" difference(s)):\n");
+                    for (String diff : diffs) {
+                        msg.append("  ").append(diff).append('\n');
+                    }
+
+                    String expected = MAPPER.writerWithDefaultPrettyPrinter().writeValueAsString(originalTree);
+                    String actual = MAPPER.writerWithDefaultPrettyPrinter().writeValueAsString(finalTree);
+                    throw buildAssertionError(msg.toString(), expected, actual);
+                }
+            }
+        } catch (IOException e) {
+            throw new UncheckedIOException("Failed to parse JSON for tree comparison", e);
+        }
+    }
+
+    private static <T> ByteArrayOutputStream roundTrip(InputStream stream, PojoSerializer<T> serializer) {
+        T event = serializer.fromJson(stream);
+        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+        serializer.toJson(event, outputStream);
+        return outputStream;
+    }
+
+    private static byte[] toBytes(InputStream stream) throws IOException {
+        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+        byte[] chunk = new byte[4096];
+        int n;
+        while ((n = stream.read(chunk)) != -1) {
+            buffer.write(chunk, 0, n);
+        }
+        return buffer.toByteArray();
+    }
+
+    /**
+     * Tries to create an opentest4j AssertionFailedError for rich IDE diff
+     * support. Falls back to plain AssertionError if opentest4j is not on
+     * the classpath.
+     */
+    private static AssertionError buildAssertionError(String message, String expected, String actual) {
+        try {
+            // opentest4j is provided by JUnit Platform (5.x) and enables
+            // IDE diff viewers to show expected vs actual side-by-side.
+            Class<?> cls = Class.forName("org.opentest4j.AssertionFailedError");
+            return (AssertionError) cls
+                    .getConstructor(String.class, Object.class, Object.class)
+                    .newInstance(message, expected, actual);
+        } catch (ReflectiveOperationException e) {
+            return new AssertionError(message + "\nExpected:\n" + expected + "\nActual:\n" + actual);
+        }
+    }
+}

aws-lambda-java-tests/src/test/java/com/amazonaws/services/lambda/runtime/tests/EventLoaderTest.java

@@ -81,6 +81,12 @@ public void testLoadAPIGatewayV2CustomAuthorizerEvent() {
 
         assertThat(event).isNotNull();
         assertThat(event.getRequestContext().getHttp().getMethod()).isEqualTo("POST");
+        // getTime() converts the raw string "12/Mar/2020:19:03:58 +0000" into a DateTime object;
+        // Jackson then serializes it as ISO-8601 "2020-03-12T19:03:58.000Z"
+        assertThat(event.getRequestContext().getTime().toInstant().getMillis())
+                .isEqualTo(DateTime.parse("2020-03-12T19:03:58.000Z").toInstant().getMillis());
+        // getTimeEpoch() converts the raw long into an Instant;
+        // Jackson then serializes it as a decimal seconds value
         assertThat(event.getRequestContext().getTimeEpoch()).isEqualTo(Instant.ofEpochMilli(1583348638390L));
     }
 
@@ -136,6 +142,9 @@ public void testLoadLexEvent() {
         assertThat(event.getCurrentIntent().getName()).isEqualTo("BookHotel");
         assertThat(event.getCurrentIntent().getSlots()).hasSize(4);
         assertThat(event.getBot().getName()).isEqualTo("BookTrip");
+        // Jackson leniently coerces the JSON number for "Nights" into a String
+        // because slots is typed as Map<String, String>
+        assertThat(event.getCurrentIntent().getSlots().get("Nights")).isInstanceOf(String.class);
     }
 
     @Test
@@ -159,6 +168,10 @@ public void testLoadMSKFirehoseEvent() {
         assertThat(event.getRecords().get(0).getKafkaRecordValue().array()).asString().isEqualTo("{\"Name\":\"Hello World\"}");
         assertThat(event.getRecords().get(0).getApproximateArrivalTimestamp()).asString().isEqualTo("1716369573887");
         assertThat(event.getRecords().get(0).getMskRecordMetadata()).asString().isEqualTo("{offset=0, partitionId=1, approximateArrivalTimestamp=1716369573887}");
+        // Jackson leniently coerces the JSON number in mskRecordMetadata into a String
+        // because the map is typed as Map<String, String>
+        Map<String, String> metadata = event.getRecords().get(0).getMskRecordMetadata();
+        assertThat(metadata.get("approximateArrivalTimestamp")).isInstanceOf(String.class);
     }
 
     @Test
@@ -408,6 +421,8 @@ public void testLoadRabbitMQEvent() {
                 .returns("AIDACKCEVSQ6C2EXAMPLE", from(RabbitMQEvent.BasicProperties::getUserId))
                 .returns(80, from(RabbitMQEvent.BasicProperties::getBodySize))
                 .returns("Jan 1, 1970, 12:33:41 AM", from(RabbitMQEvent.BasicProperties::getTimestamp));
+        // Jackson leniently coerces the JSON string "60000" for expiration into int
+        // because the model field is typed as int
 
         Map<String, Object> headers = basicProperties.getHeaders();
         assertThat(headers).hasSize(3);