Add end-to-end integration tests

.github/test-matrix.json

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+{
+  "arch": [
+    {
+      "runner": "ubuntu-latest",
+      "label": "x64",
+      "sam_arch": "x86_64",
+      "java_suffix": "X64"
+    },
+    {
+      "runner": "ubuntu-24.04-arm",
+      "label": "arm64",
+      "sam_arch": "arm64",
+      "java_suffix": "ARM64"
+    }
+  ]
+}

.github/workflows/build-integration-test.yml

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+# this workflow verifies that the integration test Lambda function builds successfully.
+# it does NOT deploy or run the tests (that requires AWS credentials and is done in
+# run-integration-test.yml).
+
+name: Build integration tests
+
+on:
+  push:
+    branches: [ main ]
+    paths:
+      - 'aws-lambda-java-log4j2/**'
+      - 'aws-lambda-java-core/**'
+      - 'lambda-integration-tests/**'
+  pull_request:
+    branches: [ '*' ]
+    paths:
+      - 'aws-lambda-java-log4j2/**'
+      - 'aws-lambda-java-core/**'
+      - 'lambda-integration-tests/**'
+      - '.github/workflows/build-integration-test.yml'
+
+permissions:
+  contents: read
+
+jobs:
+  load-matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set.outputs.matrix }}
+    steps:
+      - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+
+      - name: Load test matrix
+        id: set
+        run: |
+          MATRIX=$(jq -c '.' .github/test-matrix.json)
+          echo "matrix=${MATRIX}" >> "$GITHUB_OUTPUT"
+
+  build-arch:
+    needs: load-matrix
+    runs-on: ${{ matrix.arch.runner }}
+    strategy:
+      fail-fast: false
+      matrix: ${{ fromJson(needs.load-matrix.outputs.matrix) }}
+    name: "build (${{ matrix.arch.label }})"
+    steps:
+      - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+
+      - name: Set up JDK
+        uses: actions/setup-java@1bcf9fb12cf4aa7d266a90ae39939e61372fe520 # v5.4.0
+        with:
+          java-version: |
+            8
+            21
+          distribution: corretto
+          cache: maven
+
+      - name: Install core with Maven
+        run: |
+          export JAVA_HOME=$JAVA_HOME_8_${{ matrix.arch.java_suffix }}
+          mvn -B install --file aws-lambda-java-core/pom.xml
+
+      - name: Install log4j2 with Maven
+        run: |
+          export JAVA_HOME=$JAVA_HOME_8_${{ matrix.arch.java_suffix }}
+          mvn -B install --file aws-lambda-java-log4j2/pom.xml
+
+      # build the integration test function
+      # this verifies that the function compiles and packages correctly.
+      # the tests will run in run-integration-test.yml which deploys to AWS.
+      - name: Package integration test function
+        run: |
+          export JAVA_HOME=$JAVA_HOME_21_${{ matrix.arch.java_suffix }}
+          mvn -B package --file lambda-integration-tests/log4j2-test-function/pom.xml
+
+  build:
+    needs: build-arch
+    if: always()
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check build results
+        run: |
+          if [ "${{ needs.build-arch.result }}" != "success" ]; then
+            echo "Build failed on one or more architectures"
+            exit 1
+          fi

.github/workflows/run-integration-test.yml

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+# this workflow deploys a Lambda function that uses aws-lambda-java-log4j2,
+# invokes it, and verifies that logs arrive in CloudWatch. 
+
+name: Run integration tests
+
+permissions:
+  id-token: write
+  contents: read
+
+on:
+  workflow_dispatch:
+  push:
+    branches: [ main ]
+    paths:
+      - 'aws-lambda-java-log4j2/**'
+      - 'aws-lambda-java-core/**'
+      - 'lambda-integration-tests/**'
+
+jobs:
+  load-matrix:
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set.outputs.matrix }}
+    steps:
+      - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+
+      - name: Load test matrix
+        id: set
+        run: |
+          MATRIX=$(jq -c '.' .github/test-matrix.json)
+          echo "matrix=${MATRIX}" >> "$GITHUB_OUTPUT"
+
+  run-integration-tests:
+    needs: load-matrix
+    # Only run on the main repo, not forks
+    if: ${{ github.repository_owner == 'aws' }}
+    runs-on: ${{ matrix.arch.runner }}
+    strategy:
+      fail-fast: false
+      matrix: ${{ fromJson(needs.load-matrix.outputs.matrix) }}
+    name: "integration-test (${{ matrix.arch.label }})"
+    concurrency:
+      group: integration-test-${{ matrix.arch.label }}
+      cancel-in-progress: false
+    steps:
+      - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+
+      - name: Set up JDK
+        uses: actions/setup-java@1bcf9fb12cf4aa7d266a90ae39939e61372fe520 # v5.4.0
+        with:
+          java-version: |
+            8
+            21
+          distribution: corretto
+          cache: maven
+
+      - name: Install SAM CLI
+        uses: aws-actions/setup-sam@f84ec7d548307efafe33230528756de3c5841a17 # v2
+        with:
+          use-installer: true
+
+      - name: Configure AWS credentials
+        uses: aws-actions/configure-aws-credentials@8df5847569e6427dd6c4fb1cf565c83acfa8afa7 # v6.0.0
+        with:
+          role-to-assume: ${{ secrets.AWS_ROLE_LOG4J2_INTEG_TEST }}
+          role-session-name: GitHubActionsLog4j2IntegTest
+          aws-region: ${{ secrets.AWS_REGION_LOG4J2_INTEG_TEST }}
+
+      - name: Install core with Maven
+        run: |
+          export JAVA_HOME=$JAVA_HOME_8_${{ matrix.arch.java_suffix }}
+          mvn -B install --file aws-lambda-java-core/pom.xml
+
+      - name: Install log4j2 with Maven
+        run: |
+          export JAVA_HOME=$JAVA_HOME_8_${{ matrix.arch.java_suffix }}
+          mvn -B install --file aws-lambda-java-log4j2/pom.xml
+
+      - name: Build SAM stack
+        run: |
+          export JAVA_HOME=$JAVA_HOME_21_${{ matrix.arch.java_suffix }}
+          cd lambda-integration-tests && sam build
+
+      - name: Validate SAM stack
+        run: cd lambda-integration-tests && sam validate --lint
+
+      - name: Deploy stack
+        id: deploy_stack
+        env:
+          AWS_REGION: ${{ secrets.AWS_REGION_LOG4J2_INTEG_TEST }}
+        run: |
+          cd lambda-integration-tests
+          stackName="aws-lambda-java-log4j2-integ-test-${{ matrix.arch.label }}-$GITHUB_RUN_ID"
+          echo "STACK_NAME=$stackName" >> "$GITHUB_OUTPUT"
+          echo "Stack name = $stackName"
+          sam deploy \
+            --stack-name "${stackName}" \
+            --parameter-overrides "ParameterKey=LambdaRole,ParameterValue=${{ secrets.AWS_LAMBDA_ROLE_LOG4J2_INTEG_TEST }} ParameterKey=Architecture,ParameterValue=${{ matrix.arch.sam_arch }}" \
+            --no-confirm-changeset \
+            --no-progressbar \
+            --s3-bucket "${{ secrets.S3_BUCKET_LOG4J2_INTEG_TEST }}" \
+            --capabilities CAPABILITY_IAM \
+            2>&1 | tee /tmp/sam-deploy.log | tail -n 20
+          LOG4J2_TEST_FUNCTION=$(sam list stack-outputs --stack-name "${stackName}" --output json | jq -r '.[] | select(.OutputKey=="Log4j2TestFunction") | .OutputValue')
+          echo "LOG4J2_TEST_FUNCTION=$LOG4J2_TEST_FUNCTION" >> "$GITHUB_OUTPUT"
+          echo "Function name: $LOG4J2_TEST_FUNCTION"
+
+      - name: Run integration test
+        env:
+          LOG4J2_TEST_FUNCTION: ${{ steps.deploy_stack.outputs.LOG4J2_TEST_FUNCTION }}
+          AWS_REGION: ${{ secrets.AWS_REGION_LOG4J2_INTEG_TEST }}
+        run: ./lambda-integration-tests/run-tests.sh
+
+      - name: Cleanup
+        if: always() && steps.deploy_stack.outputs.STACK_NAME
+        env:
+          AWS_REGION: ${{ secrets.AWS_REGION_LOG4J2_INTEG_TEST }}
+          STACK_NAME: ${{ steps.deploy_stack.outputs.STACK_NAME }}
+        run: |
+          sam delete --stack-name "${STACK_NAME}" --no-prompts --region "${AWS_REGION}"

lambda-integration-tests/log4j2-test-function/pom.xml

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+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/maven-v4_0_0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.amazonaws</groupId>
+    <artifactId>log4j2-integration-test-function</artifactId>
+    <version>1.0.0</version>
+    <packaging>jar</packaging>
+
+    <name>Log4j2 Integration Test Function</name>
+    <description>
+        Lambda function used to verify that aws-lambda-java-log4j2 correctly emits logs to CloudWatch.
+    </description>
+
+    <properties>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <log4j.version>2.25.4</log4j.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.amazonaws</groupId>
+            <artifactId>aws-lambda-java-core</artifactId>
+            <version>1.4.0</version>
+        </dependency>
+        <dependency>
+            <groupId>com.amazonaws</groupId>
+            <artifactId>aws-lambda-java-log4j2</artifactId>
+            <version>1.6.4</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.logging.log4j</groupId>
+            <artifactId>log4j-core</artifactId>
+            <version>${log4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.logging.log4j</groupId>
+            <artifactId>log4j-api</artifactId>
+            <version>${log4j.version}</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <version>3.6.1</version>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>shade</goal>
+                        </goals>
+                        <configuration>
+                            <transformers>
+                                <transformer
+                                    implementation="com.github.edwgiz.mavenShadePlugin.log4j2CacheTransformer.PluginsCacheFileTransformer">
+                                </transformer>
+                            </transformers>
+                        </configuration>
+                    </execution>
+                </executions>
+                <dependencies>
+                    <dependency>
+                        <groupId>com.github.edwgiz</groupId>
+                        <artifactId>maven-shade-plugin.log4j2-cachefile-transformer</artifactId>
+                        <version>2.8.1</version>
+                    </dependency>
+                </dependencies>
+            </plugin>
+        </plugins>
+    </build>
+</project>

lambda-integration-tests/log4j2-test-function/src/main/java/integ/Log4j2TestHandler.java

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+package integ;
+
+import com.amazonaws.services.lambda.runtime.Context;
+import com.amazonaws.services.lambda.runtime.RequestHandler;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import java.util.Map;
+
+/**
+ * integration test handler that logs a marker string using Log4j2 with the LambdaAppender.
+ * the test verifies that the marker appears in CloudWatch Logs, confirming end-to-end
+ * log delivery through the aws-lambda-java-log4j2 library.
+ */
+public class Log4j2TestHandler implements RequestHandler<Map<String, String>, String> {
+
+    private static final Logger logger = LogManager.getLogger(Log4j2TestHandler.class);
+
+    @Override
+    public String handleRequest(Map<String, String> event, Context context) {
+        String marker = event.getOrDefault("marker", "NO_MARKER_PROVIDED");
+
+        logger.info("INTEG_TEST_MARKER: {}", marker);
+        logger.debug("Debug level message with marker: {}", marker);
+        logger.warn("Warning level message with marker: {}", marker);
+        logger.error("Error level message with marker: {}", marker);
+
+        return "OK:" + marker;
+    }
+}

lambda-integration-tests/log4j2-test-function/src/main/resources/log4j2.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<Configuration status="WARN">
+  <Appenders>
+    <Lambda name="Lambda" format="${env:AWS_LAMBDA_LOG_FORMAT:-TEXT}">
+      <LambdaTextFormat>
+        <PatternLayout>
+          <pattern>%d{yyyy-MM-dd HH:mm:ss} %X{AWSRequestId} %-5p %c{1}:%L - %m%n</pattern>
+        </PatternLayout>
+      </LambdaTextFormat>
+    </Lambda>
+  </Appenders>
+  <Loggers>
+    <Root level="DEBUG">
+      <AppenderRef ref="Lambda" />
+    </Root>
+  </Loggers>
+</Configuration>