As a collection

Extraction assertions

Make a topic feel like a collection. Useful when you want to assert over every published key, every payload value, or every extracted JsonPath value.

Start with KafkaAssertions.assertThatTopic(topic) and then switch into an extracted-values assertion chain.

Extraction entry points

Property	Default	Description
`extractingKeys()`	—	preserves topic read order
`extractingValues()`	—	raw string values
`extractingValues(Class<V>)`	—	JSON DTOs, Avro or Protobuf types — uses type auto-detection
`extractingJsonPath(String)`	—	evaluates the JsonPath against each string payload
`extractingJsonPath(Class<V>, String)`	—	deserializes first, then evaluates the JsonPath

All extraction methods return KafkaValuesAssert, which exposes normal AssertJ list assertions like containsExactly(...), containsExactlyInAnyOrder(...), containsOnly(...), hasSize(...), allSatisfy(...), anySatisfy(...), and noneSatisfy(...).

Keys

Java

assertThatTopic("orders-topic")
    .extractingKeys()
    .containsExactly("order-1", "order-2");

assertThatTopic("orders-topic")
    .extractingKeys()
    .containsExactly("order-1", "order-2");

Raw string payloads

Java

assertThatTopic("orders-topic")
    .extractingJsonPath("$.product")
    .containsExactly("Widget A", "Widget B");

assertThatTopic("orders-topic")
    .extractingJsonPath("$.product")
    .containsExactly("Widget A", "Widget B");

Java

assertThatTopic("orders-topic")
    .extractingValues()
    .containsOnly(
        "{\"status\":\"CREATED\"}",
        "{\"status\":\"FAILED\"}");

assertThatTopic("orders-topic")
    .extractingValues()
    .containsOnly(
        "{\"status\":\"CREATED\"}",
        "{\"status\":\"FAILED\"}");

Typed JSON payloads

Java

assertThatTopic("orders-topic")
    .extractingJsonPath(OrderEvent.class, "$.product")
    .containsExactlyInAnyOrder("Widget A", "Widget B");

assertThatTopic("orders-topic")
    .extractingJsonPath(OrderEvent.class, "$.product")
    .containsExactlyInAnyOrder("Widget A", "Widget B");

Java

assertThatTopic("orders-topic")
    .extractingValues(OrderEvent.class)
    .allSatisfy(order -> assertThat(order.getQuantity()).isPositive())
    .anySatisfy(order -> assertThat(order.getProduct()).isEqualTo("Widget A"));

assertThatTopic("orders-topic")
    .extractingValues(OrderEvent.class)
    .allSatisfy(order -> assertThat(order.getQuantity()).isPositive())
    .anySatisfy(order -> assertThat(order.getProduct()).isEqualTo("Widget A"));

Typed Avro payloads

Avro GenericRecord

Java

assertThatTopic("trades-topic")
    .extractingJsonPath(GenericRecord.class, "$.message")
    .containsExactly("Trade created", "Trade booked");

assertThatTopic("trades-topic")
    .extractingJsonPath(GenericRecord.class, "$.message")
    .containsExactly("Trade created", "Trade booked");

Avro SpecificRecord

Java

assertThatTopic("trades-topic")
    .extractingJsonPath(TradeEvent.class, "$.symbol")
    .containsExactly("AAPL", "MSFT");

assertThatTopic("trades-topic")
    .extractingJsonPath(TradeEvent.class, "$.symbol")
    .containsExactly("AAPL", "MSFT");

Failure behavior

JsonPath extraction fails fast when:

a payload is not valid JSON for the requested extraction
a record does not contain the requested path

The failure message includes the topic name, the JsonPath, and the failing record index so it's obvious which record broke the expectation.