added tests for check class

core/src/test/java/jef/util/CheckTest.java

@@ -0,0 +1,32 @@
+package jef.util;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.UUID;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class CheckTest {
+    @Test
+    void notNull_paramNotNull() {
+        //setup
+        var obj = new Object();
+
+        //test
+        var ret =  Check.notNull(obj, "obj") ;
+
+        //assert
+        assertEquals(obj, ret);
+    }
+
+    @Test
+    void notNull_paramNull() {
+        //setup
+        var varName = UUID.randomUUID().toString();
+
+        //test & assert
+        var ex = assertThrows(IllegalArgumentException.class, () -> Check.notNull(null, varName));
+        assertEquals(varName + " must be not null", ex.getMessage());
+    }
+}