Add method to convert output topic to List

README.md

@@ -101,9 +101,8 @@ To get the output, `TestTopology` provides two methods: `.streamOutput()` and `.
 They behave just like the input with regard to the number of output topics.
 Using the stream version simulates Kafka's stream-semantics, meaning that a key can be present many times in an output stream, whereas the table-semantics only output the newest value of each key.
 
-To check the output records, you can call `.expectNextRecord()` to indicate that the output should not be empty.
-You can then inspect the record with `.hasKey(K key)` and `.hasValue(V value)`.
-Both are optional, but highly recommended so that your output is always valid.
+To check the output records, you can call `.expectNextRecord()` and then chain `.hasKey(K key)`, `.hasKeySatisfying(Consumer<K> requirements)`, `.hasValue(V value)` or `.hasValueSatisfying(Consumer<V> requirements)` to this call.
+Note that calling `.expectNextRecord()` by itself without chaining at least one of the `.has*` methods will not check for the existence of a next record!
 
 Once you expect no further records, call `.expectNoMoreRecord()` to indicate the end of the output stream.
 
@@ -143,6 +142,29 @@ void shouldReturnCorrectIteratorTable() {
 }
 ```
 
+Alternatively, you can convert the output to `List` for use with your assertion framework. Here is an example of this with [AssertJ](http://joel-costigliola.github.io/assertj/).
+
+```java
+@Test
+void shouldConvertStreamOutputToList(){
+    this.testTopology.input()
+        .add("cat")
+        .add("dog")
+        .add("bird");
+
+    final List<ProducerRecord<String, Long>>outputs = this.testTopology.streamOutput()
+        .withSerde(Serdes.String(), Serdes.Long())
+        .toList();
+
+    assertThat(outputs)
+        .extracting(ProducerRecord::key)
+        .containsExactly("cat", "dog", "bird");
+    assertThat(outputs)
+        .extracting(ProducerRecord::value)
+        .containsExactly(1L, 1L, 1L);
+}
+```
+
 #### More Examples
 
 You can find many more tests

fluent-kafka-streams-tests-junit4/src/test/java/com/bakdata/fluent_kafka_streams_tests/junit4/WordCountTest.java

@@ -1,7 +1,7 @@
 /*
  * MIT License
  *
- * Copyright (c) 2019 bakdata GmbH
+ * Copyright (c) 2024 bakdata GmbH
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -244,4 +244,64 @@ public void shouldBeDoneAfterSingleWord() {
     public void shouldDoNothingOnEmptyInput() {
         this.testTopology.streamOutput().expectNoMoreRecord().and().expectNoMoreRecord().toBeEmpty();
     }
+
+    @Test
+    public void shouldConvertStreamOutputToList() {
+        this.testTopology.input()
+                .add("bla")
+                .add("blub")
+                .add("bla");
+
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.streamOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .extracting(ProducerRecord::key)
+                .containsExactly("bla", "blub", "bla");
+        assertThat(outputs)
+                .extracting(ProducerRecord::value)
+                .containsExactly(1L, 1L, 2L);
+    }
+
+    @Test
+    public void shouldConvertTableOutputToList() {
+        this.testTopology.input()
+                .add("bla")
+                .add("blub")
+                .add("bla");
+
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.tableOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .extracting(ProducerRecord::key)
+                .containsExactly("bla", "blub");
+        assertThat(outputs)
+                .extracting(ProducerRecord::value)
+                .containsExactly(2L, 1L);
+    }
+
+    @Test
+    public void shouldConvertEmptyStreamOutputToEmptyList() {
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.streamOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .isInstanceOf(List.class)
+                .isEmpty();
+    }
+
+    @Test
+    public void shouldConvertEmptyTableOutputToEmptyList() {
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.tableOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .isInstanceOf(List.class)
+                .isEmpty();
+    }
 }

fluent-kafka-streams-tests-junit5/src/test/java/com/bakdata/fluent_kafka_streams_tests/junit5/WordCountTest.java

@@ -1,7 +1,7 @@
 /*
  * MIT License
  *
- * Copyright (c) 2019 bakdata GmbH
+ * Copyright (c) 2024 bakdata GmbH
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -244,4 +244,64 @@ void shouldBeDoneAfterSingleWord() {
     void shouldDoNothingOnEmptyInput() {
         this.testTopology.streamOutput().expectNoMoreRecord().and().expectNoMoreRecord().toBeEmpty();
     }
+
+    @Test
+    void shouldConvertStreamOutputToList() {
+        this.testTopology.input()
+                .add("bla")
+                .add("blub")
+                .add("bla");
+
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.streamOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .extracting(ProducerRecord::key)
+                .containsExactly("bla", "blub", "bla");
+        assertThat(outputs)
+                .extracting(ProducerRecord::value)
+                .containsExactly(1L, 1L, 2L);
+    }
+
+    @Test
+    void shouldConvertTableOutputToList() {
+        this.testTopology.input()
+                .add("bla")
+                .add("blub")
+                .add("bla");
+
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.tableOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .extracting(ProducerRecord::key)
+                .containsExactly("bla", "blub");
+        assertThat(outputs)
+                .extracting(ProducerRecord::value)
+                .containsExactly(2L, 1L);
+    }
+
+    @Test
+    void shouldConvertEmptyStreamOutputToEmptyList() {
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.streamOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .isInstanceOf(List.class)
+                .isEmpty();
+    }
+
+    @Test
+    void shouldConvertEmptyTableOutputToEmptyList() {
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.tableOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .isInstanceOf(List.class)
+                .isEmpty();
+    }
 }

fluent-kafka-streams-tests/src/main/java/com/bakdata/fluent_kafka_streams_tests/BaseOutput.java

@@ -1,7 +1,7 @@
 /*
  * MIT License
  *
- * Copyright (c) 2019 bakdata GmbH
+ * Copyright (c) 2024 bakdata GmbH
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -24,6 +24,8 @@
 
 package com.bakdata.fluent_kafka_streams_tests;
 
+import java.util.ArrayList;
+import java.util.List;
 import org.apache.kafka.clients.producer.ProducerRecord;
 import org.apache.kafka.common.serialization.Serde;
 import org.apache.kafka.streams.TestOutputTopic;
@@ -114,6 +116,22 @@ public TestOutput<K, V> asStream() {
         return new StreamOutput<>(this.testDriver, this.topic, this.keySerde, this.valueSerde);
     }
 
+    /**
+     * Convert the output to a {@link java.util.List}. In case the current instance of this class is a
+     * {@link StreamOutput}, the output will be converted to List with {@link org.apache.kafka.streams.kstream.KStream}
+     * semantics (each key multiple times). In case the current instance of this class is a {@link TableOutput}, the
+     * output will be converted to List with {@link org.apache.kafka.streams.kstream.KTable} semantics (each key only
+     * once).
+     *
+     * @return A {@link java.util.List} representing the output
+     */
+    @Override
+    public List<ProducerRecord<K, V>> toList() {
+        final List<ProducerRecord<K, V>> list = new ArrayList<>();
+        this.iterator().forEachRemaining(list::add);
+        return list;
+    }
+
     // ==================
     // Non-public methods
     // ==================

fluent-kafka-streams-tests/src/main/java/com/bakdata/fluent_kafka_streams_tests/TestOutput.java

@@ -1,7 +1,7 @@
 /*
  * MIT License
  *
- * Copyright (c) 2023 bakdata GmbH
+ * Copyright (c) 2024 bakdata GmbH
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -24,6 +24,7 @@
 
 package com.bakdata.fluent_kafka_streams_tests;
 
+import java.util.List;
 import org.apache.kafka.clients.producer.ProducerRecord;
 import org.apache.kafka.common.serialization.Serde;
 
@@ -144,8 +145,16 @@ default <VR> TestOutput<K, VR> withValueType(final Class<VR> valueType) {
      * <p>This is the default, there should usually be no need to call this method.</p>
      * <p>Note: once the first value of the stream has been read or the iterator has be called, you cannot switch
      * between the output types any more.</p>
+     *
      * @return Current output with {@link org.apache.kafka.streams.kstream.KStream} semantics
      */
     TestOutput<K, V> asStream();
+
+    /**
+     * Convert the output to a {@link java.util.List}.
+     *
+     * @return A {@link java.util.List} representing the output
+     */
+    List<ProducerRecord<K, V>> toList();
 }
 

fluent-kafka-streams-tests/src/test/java/com/bakdata/fluent_kafka_streams_tests/WordCountTest.java

@@ -1,7 +1,7 @@
 /*
  * MIT License
  *
- * Copyright (c) 2023 bakdata GmbH
+ * Copyright (c) 2024 bakdata GmbH
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -387,4 +387,64 @@ void shouldBeDoneAfterSingleWord() {
     void shouldDoNothingOnEmptyInput() {
         this.testTopology.streamOutput().expectNoMoreRecord().and().expectNoMoreRecord().toBeEmpty();
     }
+
+    @Test
+    void shouldConvertStreamOutputToList() {
+        this.testTopology.input()
+                .add("bla")
+                .add("blub")
+                .add("bla");
+
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.streamOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .extracting(ProducerRecord::key)
+                .containsExactly("bla", "blub", "bla");
+        assertThat(outputs)
+                .extracting(ProducerRecord::value)
+                .containsExactly(1L, 1L, 2L);
+    }
+
+    @Test
+    void shouldConvertTableOutputToList() {
+        this.testTopology.input()
+                .add("bla")
+                .add("blub")
+                .add("bla");
+
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.tableOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .extracting(ProducerRecord::key)
+                .containsExactly("bla", "blub");
+        assertThat(outputs)
+                .extracting(ProducerRecord::value)
+                .containsExactly(2L, 1L);
+    }
+
+    @Test
+    void shouldConvertEmptyStreamOutputToEmptyList() {
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.streamOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .isInstanceOf(List.class)
+                .isEmpty();
+    }
+
+    @Test
+    void shouldConvertEmptyTableOutputToEmptyList() {
+        final List<ProducerRecord<String, Long>> outputs = this.testTopology.tableOutput()
+                .withSerde(Serdes.String(), Serdes.Long())
+                .toList();
+
+        assertThat(outputs)
+                .isInstanceOf(List.class)
+                .isEmpty();
+    }
 }