Add documentation about overriding properties in unit tests (#251)

* Add documentation about overriding properties in unit tests

* sonar

README.md

@@ -53,6 +53,8 @@ need to do:
 * [Open Telemetry](#open-telemetry)
 * [Swagger](#swagger)
 * [Testing](#testing)
+  * [Create your first test](#create-your-first-test)
+  * [Override Properties](#override-properties)
 * [Motivation](#motivation)
 * [Contribution](#contribution)
 
@@ -501,6 +503,8 @@ Both can be customized by using the [Springdoc properties](https://springdoc.org
 
 Kstreamplify eases the use of the Topology Test Driver for testing Kafka Streams application.
 
+### Create your first test
+
 You can create a test class that extends `KafkaStreamsStarterTest`, override
 the `KafkaStreamsStarterTest#getKafkaStreamsStarter()` to provide your `KafkaStreamsStarter` implementation, 
 and start writing your tests.
@@ -543,6 +547,22 @@ public class MyKafkaStreamsTest extends KafkaStreamsStarterTest {
 }
 ```
 
+### Override Properties
+
+Kstreamplify runs the tests with default properties. 
+It is possible to provide additional properties or override the default ones:
+
+```java
+public class MyKafkaStreamsTest extends KafkaStreamsStarterTest {
+    @Override
+    protected Map<String, String> getSpecificProperties() {
+        return Map.of(
+            STATE_DIR_CONFIG, "/tmp/kafka-streams"
+        );
+    }
+}
+```
+
 ## Motivation
 
 Developing applications with Kafka Streams can be challenging and often raises many questions for developers. It

kstreamplify-core-test/src/main/java/com/michelin/kstreamplify/KafkaStreamsStarterTest.java

@@ -14,7 +14,7 @@
 import java.nio.file.Paths;
 import java.time.Instant;
 import java.util.Collections;
-import java.util.HashMap;
+import java.util.Map;
 import java.util.Properties;
 import org.apache.kafka.common.serialization.StringDeserializer;
 import org.apache.kafka.streams.StreamsBuilder;
@@ -82,7 +82,7 @@ private Properties getProperties() {
         properties.setProperty(StreamsConfig.STATE_DIR_CONFIG, STATE_DIR + getClass().getSimpleName());
 
         // Add specific properties or overwrite default properties
-        HashMap<String, String> propertiesMap = getSpecificProperties();
+        Map<String, String> propertiesMap = getSpecificProperties();
         if (propertiesMap != null && !propertiesMap.isEmpty()) {
             properties.putAll(propertiesMap);
         }
@@ -111,8 +111,8 @@ protected Instant getInitialWallClockTime() {
      *
      * @return new/overwrite properties
      */
-    protected HashMap<String, String> getSpecificProperties() {
-        return new HashMap<>();
+    protected Map<String, String> getSpecificProperties() {
+        return Collections.emptyMap();
     }
 
     /**

kstreamplify-core-test/src/test/java/com/michelin/kstreamplify/OverridePropertiesTest.java

@@ -4,7 +4,7 @@
 
 import com.michelin.kstreamplify.context.KafkaStreamsExecutionContext;
 import com.michelin.kstreamplify.initializer.KafkaStreamsStarter;
-import java.util.HashMap;
+import java.util.Map;
 import java.util.Properties;
 import org.apache.kafka.streams.StreamsBuilder;
 import org.junit.jupiter.api.Assertions;
@@ -25,21 +25,21 @@ public String dlqTopic() {
 
             @Override
             public void topology(StreamsBuilder streamsBuilder) {
+                // Do nothing
             }
         };
     }
 
     /**
      * Overwrite the default storage path.
      *
-     * @return the new/overwrite properties
+     * @return the new properties
      */
     @Override
-    protected HashMap<String, String> getSpecificProperties() {
-        HashMap<String, String> propertiesMap = new HashMap<>();
-        propertiesMap.put(STATE_DIR_CONFIG, SPECIFIC_STORAGE_PATH);
-
-        return propertiesMap;
+    protected Map<String, String> getSpecificProperties() {
+        return Map.of(
+            STATE_DIR_CONFIG, SPECIFIC_STORAGE_PATH
+        );
     }
 
     /**
@@ -50,5 +50,4 @@ void shouldValidateStorageDirHasBeenOverride() {
         Properties properties = KafkaStreamsExecutionContext.getProperties();
         Assertions.assertEquals(SPECIFIC_STORAGE_PATH, properties.getProperty(STATE_DIR_CONFIG));
     }
-
 }