Add transaction tests for KafkaContainer and ConfluentKafkaContainer

[aymenjam]

Kafka transactions need transaction.state.log.replication.factor and transaction.state.log.min.isr set to 1 on a single broker. Without them, initTransactions() times out while waiting for InitProducerId.

KafkaContainer and ConfluentKafkaContainer already set these values, but no test checks it. This PR adds a test for each class. The test commits a transaction and reads the message with a read_committed consumer.

Refs #1816

Summary by CodeRabbit

• Tests
  • Expanded Kafka container test coverage to verify that committed transactional messages are received by consumers configured to read committed records. The checks run against both Confluent Kafka and Apache Kafka containers.

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📥 Commits

Reviewing files that changed from the base of the PR and between 8e54951 and ea074e5.

📒 Files selected for processing (3)

• modules/kafka/src/test/java/org/testcontainers/AbstractKafka.java
• modules/kafka/src/test/java/org/testcontainers/kafka/ConfluentKafkaContainerTest.java
• modules/kafka/src/test/java/org/testcontainers/kafka/KafkaContainerTest.java

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📝 Walkthrough

Walkthrough

Adds a shared Kafka test that commits a record in a transaction and checks that a read_committed consumer receives it. The test runs against Confluent Kafka and Apache Kafka containers.

Changes

Kafka Transaction Test Coverage

Layer / File(s)	Summary
Shared transactional test modules/kafka/src/test/java/org/testcontainers/AbstractKafka.java	Creates a topic, sends and commits a record in a transaction, and asserts that a read_committed consumer receives exactly that record within 10 seconds.
Container implementation coverage modules/kafka/src/test/java/org/testcontainers/kafka/ConfluentKafkaContainerTest.java, modules/kafka/src/test/java/org/testcontainers/kafka/KafkaContainerTest.java	Adds tests that run the shared transactional test against Confluent Kafka 7.4.0 and apache/kafka-native:3.8.0.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Other

Suggested reviewers: eddumelendez

Merge Risk: ⚪ Minimal · up to ea074

This change only adds tests for Kafka transactions on both container types and does not change production behavior. No merge-blocking risk was found.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main change: adding transaction tests for both Kafka container classes.
Description check	✅ Passed	The description explains the single-broker transaction issue, the tests being added, and the purpose of the change. It also references issue #1816.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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