test(TasksData): Add unit tests

Implemented unit tests for the TasksData class to ensure the correctness of the setReplaceMessage, getReplaceMessage, setReplaceCount, and getReplaceCount methods. These tests cover basic functionality to verify that the methods correctly set and retrieve replace messages and counts.

Rationale:
The TasksData class contains important functionality related to task data management in the application. To ensure the reliability and correctness of this class, unit tests have been added to validate its key methods. These tests provide confidence that the class behaves as expected and help maintain code quality by detecting potential regressions or bugs during development or refactoring.

src/test/java/de/danielluedecke/zettelkasten/database/TasksDataTest.java

@@ -0,0 +1,41 @@
+package de.danielluedecke.zettelkasten.database;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+import java.util.LinkedList;
+
+public class TasksDataTest {
+
+    @Test
+    void testSetReplaceMessageAndGetReplaceMessage() {
+        // Test setting and getting replace message
+        // Arrange
+        TasksData tasksData = new TasksData();
+        String expectedMessage = "Test message";
+
+        // Act
+        tasksData.setReplaceMessage(expectedMessage);
+        String actualMessage = tasksData.getReplaceMessage();
+
+        // Assert
+        assertEquals(expectedMessage, actualMessage);
+    }
+
+    @Test
+    void testSetReplaceCountAndGetReplaceCount() {
+        // Test setting and getting replace count
+        // Arrange
+        TasksData tasksData = new TasksData();
+        int expectedCount = 10;
+
+        // Act
+        tasksData.setReplaceCount(expectedCount);
+        int actualCount = tasksData.getReplaceCount();
+
+        // Assert
+        assertEquals(expectedCount, actualCount);
+    }
+
+    // Add more test methods to cover other methods in TasksData class
+
+}