test: add unit tests for HomeboxSearchProvider and SearchResponse

HomeboxSearchProviderTest verifies that ConnectionNotFoundException is
thrown when no matching connection exists in the repository.
SearchResponseTest covers the getExtra helper — null extra map, missing
key, and a present key.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

backend/src/test/java/com/vaessl/app/search/SearchResponseTest.java

@@ -0,0 +1,33 @@
+package com.vaessl.app.search;
+
+import static com.vaessl.app.Mockdata.*;
+import static org.assertj.core.api.Assertions.assertThat;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class SearchResponseTest {
+
+    @Test
+    void shouldReturnNullWhenExtraDataIsNull() {
+        SearchResponse response = new SearchResponse(MOCK_TITLE, MOCK_DESCRIPTION, null);
+
+        assertThat(response.getExtra(null)).isNull();
+    }
+
+    @Test
+    void shouldReturnNullWhenExtraDataKeyIsMissing() {
+
+        SearchResponse response = new SearchResponse(MOCK_TITLE, MOCK_DESCRIPTION, Map.of("key", "value"));
+
+        assertThat(response.getExtra("missing")).isNull();
+    }
+
+    @Test
+    void shouldReturnExtraDataValue() {
+
+        SearchResponse response = new SearchResponse(MOCK_TITLE, MOCK_DESCRIPTION, Map.of("key", "value"));
+
+        assertThat(response.getExtra("key")).contains("value");
+
+    }
+}