wip(#300): @NathanEckert is correct

The modern S3EC and SDK V2 treat reading 0 bytes
from a stream differently in at least one case:
If the Stream has no more content.

.github/workflows/ghi_300.yml

@@ -0,0 +1,49 @@
+name: ghi_300.yml
+on:
+  push:
+    branches:
+      - tony/refactor-tests
+      - 'ghi-300/**'
+
+jobs:
+  Build:
+    runs-on: ubuntu-latest
+    permissions:
+      id-token: write
+      contents: read
+
+    steps:
+      - name: Configure AWS Credentials
+        uses: aws-actions/configure-aws-credentials@v2
+        with:
+          role-to-assume: arn:aws:iam::${{ secrets.CI_AWS_ACCOUNT_ID }}:role/service-role/${{ vars.CI_AWS_ROLE }}
+          role-session-name: S3EC-Github-CI-Tests
+          aws-region: ${{ vars.CI_AWS_REGION }}
+
+      - name: Checkout Code
+        uses: actions/checkout@v3
+
+      # TODO: Add OpenJDK
+      # OpenJDK would require a different action than setup-java, so setup is more involved.
+
+      - name: Setup JDK
+        uses: actions/setup-java@v3
+        with:
+          distribution: 8
+          java-version: corretto
+          cache: 'maven'
+
+      - name: Compile
+        run: |
+          mvn --batch-mode -no-transfer-progress clean compile
+          mvn --batch-mode -no-transfer-progress test-compile
+        shell: bash
+
+      - name: Test
+        run: |
+          export AWS_S3EC_TEST_BUCKET=${{ vars.CI_S3_BUCKET }}
+          export AWS_S3EC_TEST_KMS_KEY_ID=arn:aws:kms:${{ vars.CI_AWS_REGION }}:${{ secrets.CI_AWS_ACCOUNT_ID }}:key/${{ vars.CI_KMS_KEY_ID }}
+          export AWS_S3EC_TEST_KMS_KEY_ALIAS=arn:aws:kms:${{ vars.CI_AWS_REGION }}:${{ secrets.CI_AWS_ACCOUNT_ID }}:alias/${{ vars.CI_KMS_KEY_ALIAS }}
+          export AWS_REGION=${{ vars.CI_AWS_REGION }}
+          mvn -B -ntp -DskipCompile -Dtest=software.amazon.encryption.s3.examples.TestEndOfStreamBehavior test
+        shell: bash

src/test/java/software/amazon/encryption/s3/examples/TestEndOfStreamBehavior.java

@@ -85,24 +85,15 @@ void testEndOfStreamBehavior(final S3Client client) throws Exception {
         while (byteRead != END_OF_STREAM) {
             int lenToRead = capacity - startPosition;
             System.out.println("Start position: " + startPosition + " Length to read: " + lenToRead);
-            // @NathanEckert , about https://github.com/aws/amazon-s3-encryption-client-java/issues/300
-            // Crypto Tools SOMETIMES got an Assertion Error from
-            // https://github.com/aws/aws-sdk-java-v2/blob/2.20.38/utils/src/main/java/software/amazon/awssdk/utils/async/InputStreamSubscriber.java#L110
-            // when using the Encryption Client.
-            // If we bump our Java SDK dependencies to the latest, which today is 2.26.7,
-            // than we never get the Assertion Error.
-            // Here is the PR that changes InputStreamSubscriber b/w 2.20.38 and 2.26.7:
-            // https://github.com/aws/aws-sdk-java-v2/pull/5201
-            // This makes us suspect that something else is going wrong.
-            // Otherwise, we cannot detect a difference in behavior between
-            // the S3EC V3 Client and the S3 V2 Client with respect to this code.
             byteRead = stream.read(underlyingBuffer, startPosition, lenToRead);
             System.out.println("Read " + byteRead + " bytes");
             startPosition += byteRead;
             if (byteRead == 0) {
-                // Crypto Tools cannot get this case to ever occur.
-                System.out.println("Looping indefinitely with an encryption client, as startPosition is not increasing");
-                break;
+                // Now we always get this error; we probably were always getting this error, but the log was not writing.
+                throw new AssertionError(
+                    String.format("Looping indefinitely with an encryption client, as startPosition is not increasing." +
+                            "\n lenToRead: %s \t byteRead: %s \t startPosition: %s",
+                        lenToRead, byteRead, startPosition));
             }
         }
     }