Fixed JUnit tests causing build issues due to mixing JUnit 4 & JUnit 5

partial-response/src/test/java/com/iluwatar/partialresponse/FieldJsonMapperTest.java

@@ -23,24 +23,23 @@
 
 package com.iluwatar.partialresponse;
 
-import static org.junit.Assert.assertEquals;
-
-import org.junit.Before;
-import org.junit.Test;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
 
 /**
  * tests {@link FieldJsonMapper}.
  */
-public class FieldJsonMapperTest {
-  private FieldJsonMapper mapper;
+class FieldJsonMapperTest {
+  private static FieldJsonMapper mapper;
 
-  @Before
-  public void setUp() {
+  @BeforeAll
+  static void setUp() {
     mapper = new FieldJsonMapper();
   }
 
   @Test
-  public void shouldReturnJsonForSpecifiedFieldsInVideo() throws Exception {
+  void shouldReturnJsonForSpecifiedFieldsInVideo() throws Exception {
     var fields = new String[]{"id", "title", "length"};
     var video = new Video(
         2, "Godzilla Resurgence", 120,
@@ -50,6 +49,6 @@ public class FieldJsonMapperTest {
     var jsonFieldResponse = mapper.toJson(video, fields);
 
     var expectedDetails = "{\"id\": 2,\"title\": \"Godzilla Resurgence\",\"length\": 120}";
-    assertEquals(expectedDetails, jsonFieldResponse);
+    Assertions.assertEquals(expectedDetails, jsonFieldResponse);
   }
 }