test(json-service): increase coverage to 100%

quarkus-json-service/pom.xml

@@ -42,7 +42,7 @@
                                         <limit>
                                             <counter>INSTRUCTION</counter>
                                             <value>COVEREDRATIO</value>
-                                            <minimum>0.83</minimum>
+                                            <minimum>1</minimum>
                                         </limit>
                                     </limits>
                                 </rule>

quarkus-json-service/src/test/java/ch/phoenixtechnologies/quarkus/commons/json/JsonServiceImplTest.java

@@ -17,6 +17,15 @@ class JsonServiceImplTest {
 
     record TestRecord(String name, int age) {}
 
+    static class CircularReference {
+        CircularReference reference;
+
+        @Override
+        public String toString() {
+            return "CircularReference";
+        }
+    }
+
     @Inject
     JsonServiceImpl jsonService;
 
@@ -29,6 +38,17 @@ class JsonServiceImplTest {
         assertThat(actual).as("Json should match expected value").isEqualTo(expected);
     }
 
+    @Test
+    void toJsonWithCircularReference() {
+        var circularReference = new CircularReference();
+        circularReference.reference = circularReference;
+
+        assertThatThrownBy(() -> jsonService.toJson(circularReference))
+                .as("Should throw IllegalArgumentException when input is invalid")
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessage("Unable to write object as json String: CircularReference");
+    }
+
     @Test
     void fromJsonWithClass() {
         var json = "{\"name\":\"John Doe\",\"age\":30}";