Add Note model object

src/test/java/model/NoteTest.java

@@ -0,0 +1,28 @@
+package model;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class NoteTest {
+
+    @Test
+    void requireNonNullMessage() {
+        assertThrows(NullPointerException.class, () -> new Note(1, null, "from", "to", System.currentTimeMillis(), 0));
+    }
+
+    @Test
+    void requireNonNullFrom() {
+        assertThrows(NullPointerException.class, () -> new Note(2, "message", null, "to", System.currentTimeMillis(), 0));
+    }
+
+    @Test
+    void requireNonNullTo() {
+        assertThrows(NullPointerException.class, () -> new Note(3, "message", "from", null, System.currentTimeMillis(), 0));
+    }
+
+    @Test
+    void createNew() {
+        assertDoesNotThrow(() -> new Note(4, "message", "from", "to", System.currentTimeMillis(), 5));
+    }
+}