src/main/java/device/cdPlayer/CDPlayer.java

@@ -21,17 +21,25 @@ public class CDPlayer implements Device {
 
     @Override
     public void louder() {
-
+        if(volume < 100) {
+            volume += 1;
+        } else {
+            volume = 100;
+        }
     }
 
     @Override
     public void quieter() {
-
+        if(volume > 0) {
+            volume -= 1;
+        } else {
+            volume = 0;
+        }
     }
 
     @Override
     public int getVolume() {
-        return 0;
+        return volume;
     }
 
     @Override

src/test/java/device/cdPlayer/CDPlayerTest.java

@@ -1,47 +1,52 @@
 package device.cdPlayer;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.mockito.junit.jupiter.MockitoExtension;
 
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.jupiter.api.Assertions.*;
 
+@ExtendWith(MockitoExtension.class)
 class CDPlayerTest {
-/*
-    @Test
-    void louder() {
-    }
-
-    @Test
-    void quieter() {
-    }
-
-    @Test
-    void getVolume() {
-    }
-
-    @Test
-    void next() {
-    }
-
-    @Test
-    void prev() {
-    }
-
-    @Test
-    void getInfoText() {
-    }
-
-    @Test
-    void getOptions() {
-    }
-
-    @Test
-    void chooseOption() {
-    }
 
-    @Test
-    void play() {
+    @ParameterizedTest
+    @MethodSource("quieterTestData")
+    void quieterTest(String testName,String testDirection, CDPlayer _cdPlayer,int anzClicks, int expectedResult) {
+        for (int i = 0; i < anzClicks; i++) {
+            _cdPlayer.quieter();
+        }
+
+        if(testDirection.equals("VolumeDecreased")){
+            for (int i = 0; i < 20; i++) {
+                _cdPlayer.louder();
+            }
+            for (int i = 0; i < anzClicks; i++) {
+                _cdPlayer.quieter();
+            }
+            assertThat(_cdPlayer.getVolume()).describedAs(testName).isEqualTo(expectedResult);
+        }
+        if(testDirection.equals("VolumeHasNotChanged")){
+            assertThat(_cdPlayer.getVolume()).describedAs(testName).isEqualTo(expectedResult);
+        }if(testDirection.equals("VolumeNotIncreased")){
+
+            assertThat(_cdPlayer.getVolume()).describedAs(testName).isNotEqualTo(expectedResult);
+        }
+    }
+
+    static Stream<Arguments> quieterTestData () {
+        CDPlayer cdPlayer=new CDPlayer();
+        return Stream.of(
+                Arguments.of("[getVolume() after 20x quieter() starting by 20] => VolumeHasDecreased","VolumeDecreased", cdPlayer, 19, 1),
+                Arguments.of("[getVolume() after 20x quieter() starting by 0] => VolumeHasNotChanged","VolumeHasNotChanged" ,cdPlayer,20,0),
+                Arguments.of("[getVolume() after 5x quieter() starting by 0] => VolumeNotIncreased","VolumeNotIncreased", cdPlayer,5,5)
+        );
     }
 
- */
 
 }