Combine 'Bad title' tests to @ParameterizedTest + @nullAndEmptySource

Author: codesungrape

src/test/java/com/codesungrape/hmcts/bookapi/BookServiceTest.java

@@ -11,6 +11,8 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.MethodSource;
+import org.junit.jupiter.params.provider.NullAndEmptySource;
+import org.junit.jupiter.params.provider.ValueSource;
 import org.mockito.ArgumentCaptor;
 import org.mockito.InjectMocks;
 import org.mockito.Mock;
@@ -171,51 +173,6 @@ void testCreateBook_NullRequest_ThrowsException() {
         );
     }
 
-    @Test
-    void testCreateBook_NullTitle_ThrowsException() {
-        // Arrange
-        BookRequest invalidRequest = new BookRequest(null, "Synopsis", "Author");
-
-        // Act & Assert
-        assertThrows(
-            IllegalArgumentException.class,
-            () -> {
-                testBookService.createBook(invalidRequest);
-            }
-        );
-
-        // Verify repository was never called
-        verify(testBookRepository, never()).save(any());
-    }
-
-    @Test
-    void testCreateBook_EmptyTitle_ThrowsException() {
-        // Arrange
-        BookRequest invalidRequest = new BookRequest("", "Synopsis", "Author");
-
-        // Act & Assert
-        assertThrows(
-            IllegalArgumentException.class,
-            () -> {
-                testBookService.createBook(invalidRequest);
-            }
-        );
-    }
-
-    @Test
-    void testCreateBook_BlankTitle_ThrowsException() {
-        // Arrange
-        BookRequest invalidRequest = new BookRequest("   ", "Synopsis", "Author");
-
-        // Act & Assert
-        assertThrows(
-            IllegalArgumentException.class,
-            () -> {
-                testBookService.createBook(invalidRequest);
-            }
-        );
-    }
-
     @Test
     void testCreateBook_RepositoryFailure_ThrowsException() {
         // Arrange
@@ -231,6 +188,19 @@ void testCreateBook_RepositoryFailure_ThrowsException() {
         );
     }
 
+    @ParameterizedTest
+    @NullAndEmptySource // Covers Null and "" (Empty)
+    @ValueSource(strings = {"   ", "\t", "\n"}) // Covers Blank (Spaces/Tabs)
+    void testCreateBook_InvalidTitle_ThrowsException(String invalidTitle) {
+        // Arrange
+        BookRequest invalidRequest = new BookRequest(invalidTitle, "Synopsis", "Author");
+
+        // Act & Assert
+        assertThrows(IllegalArgumentException.class, () -> {
+            testBookService.createBook(invalidRequest);
+        });
+    }
+
     // ----- EDGE cases ---------
 
     @ParameterizedTest(name = "{0}") // Display the test name