added TestRunner class

src/test/java/CalculatorTest.java

-import org.junit.Test;
-import static org.junit.Assert.*;
-
-public class CalculatorTest {
-
-
-    public static void main(String[] args) {
-        Calculator calculator = new Calculator();
-        long res = calculator.addTwo(10l, 15l);
-        assertEquals(res, 25L);
-    }
-
-
-}

src/test/java/SampleTest.java

+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class SampleTest {
+    int a = 10;
+    int b = 20;
+
+    @Test
+    public void testAdd() {
+        assertEquals( (a + b), 30 );
+    }
+}

src/test/java/TestJUnit.java

+import org.junit.Test;
+import static org.junit.Assert.*;
+
+public class TestJUnit {
+
+    @Test
+    public void testSample() {
+        String str = "JUnit";
+        assertEquals("JUnit", str);
+    }
+}

src/test/java/TestRunner.java

+import org.junit.runner.JUnitCore;
+import org.junit.runner.Result;
+import org.junit.runner.notification.Failure;
+
+import static org.junit.Assert.*;
+
+public class TestRunner {
+    public static void main(String[] args) {
+        Result result = JUnitCore.runClasses(SampleTest.class);
+        for (Failure failure : result.getFailures()) {
+            System.out.println(failure.toString());
+        }
+
+        System.out.println(result.wasSuccessful());
+    }
+}