Added tests instead of a main method

core-java-modules/core-java-11/src/main/java/com/baeldung/predicate/not/FindPeople.java

@@ -1,33 +0,0 @@
-package com.baeldung.predicate.not;
-
-import java.util.List;
-import java.util.function.Predicate;
-import java.util.stream.Collectors;
-
-import static java.util.function.Predicate.*;
-
-public class FindPeople {
-    public static void main(String[] args) {
-        List<Person> people = List.of(
-          new Person(1),
-          new Person(18),
-          new Person(2)
-        );
-
-        people.stream()
-          .filter(Person::isAdult)
-          .collect(Collectors.toList());
-
-        people.stream()
-          .filter(person -> !person.isAdult())
-          .collect(Collectors.toList());
-
-        people.stream()
-          .filter(Person::isNotAdult)
-          .collect(Collectors.toList());
-
-        people.stream()
-          .filter(not(Person::isAdult))
-          .collect(Collectors.toList());
-    }
-}

core-java-modules/core-java-11/src/test/java/com/baeldung/AppUnitTest.java

@@ -7,7 +7,7 @@ import junit.framework.TestSuite;
 /**
  * Unit test for simple App.
  */
-public class AppTest 
+public class AppUnitTest
     extends TestCase
 {
     /**
@@ -15,7 +15,7 @@ public class AppTest
      *
      * @param testName name of the test case
      */
-    public AppTest( String testName )
+    public AppUnitTest(String testName )
     {
         super( testName );
     }
@@ -25,7 +25,7 @@ public class AppTest
      */
     public static Test suite()
     {
-        return new TestSuite( AppTest.class );
+        return new TestSuite( AppUnitTest.class );
     }
 
     /**

core-java-modules/core-java-11/src/test/java/com/baeldung/java11/httpclient/test/HttpClientUnitTest.java

@@ -32,7 +32,7 @@ import java.util.stream.Collectors;
 
 import org.junit.jupiter.api.Test;
 
-public class HttpClientTest {
+public class HttpClientUnitTest {
 
     @Test
     public void shouldReturnSampleDataContentWhenConnectViaSystemProxy() throws IOException, InterruptedException, URISyntaxException {

core-java-modules/core-java-11/src/test/java/com/baeldung/java11/httpclient/test/HttpRequestUnitTest.java

@@ -19,7 +19,7 @@ import java.time.Duration;
 
 import org.junit.Test;
 
-public class HttpRequestTest {
+public class HttpRequestUnitTest {
 
     @Test
     public void shouldReturnStatusOKWhenSendGetRequest() throws IOException, InterruptedException, URISyntaxException {

core-java-modules/core-java-11/src/test/java/com/baeldung/java11/httpclient/test/HttpResponseUnitTest.java

@@ -14,7 +14,7 @@ import java.net.http.HttpResponse;
 
 import org.junit.Test;
 
-public class HttpResponseTest {
+public class HttpResponseUnitTest {
 
     @Test
     public void shouldReturnStatusOKWhenSendGetRequest() throws IOException, InterruptedException, URISyntaxException {

core-java-modules/core-java-11/src/test/java/com/baeldung/predicate/not/PersonUnitTest.java

@@ -0,0 +1,61 @@
+package com.baeldung.predicate.not;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static java.util.function.Predicate.not;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class PersonUnitTest {
+    private List<Person> people;
+
+    @BeforeEach
+    void preparePeople() {
+        people = Arrays.asList(
+          new Person(1),
+          new Person(18),
+          new Person(2)
+        );
+    }
+
+    @Test
+    void givenPeople_whenFilterIsAdult_thenOneResult() {
+        List<Person> adults = people.stream()
+          .filter(Person::isAdult)
+          .collect(Collectors.toList());
+
+        assertThat(adults).size().isEqualTo(1);
+    }
+
+    @Test
+    void givenPeople_whenFilterIsAdultNegated_thenTwoResults() {
+        List<Person> nonAdults = people.stream()
+          .filter(person -> !person.isAdult())
+          .collect(Collectors.toList());
+
+        assertThat(nonAdults).size().isEqualTo(2);
+    }
+
+    @Test
+    void givenPeople_whenFilterIsNotAdult_thenTwoResults() {
+        List<Person> nonAdults = people.stream()
+          .filter(Person::isNotAdult)
+          .collect(Collectors.toList());
+
+        assertThat(nonAdults).size().isEqualTo(2);
+    }
+
+    @Test
+    void givenPeople_whenFilterNotIsAdult_thenTwoResults() {
+        List<Person> nonAdults = people.stream()
+          .filter(not(Person::isAdult))
+          .collect(Collectors.toList());
+
+        assertThat(nonAdults).size().isEqualTo(2);
+    }
+}