Add tests for MyClipboard#getSystemClipboard

src/test/java/me/goudham/MyClipboardTest.java

@@ -0,0 +1,67 @@
+package me.goudham;
+
+import java.util.stream.Stream;
+import me.goudham.exception.UnsupportedSystemException;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import static org.hamcrest.CoreMatchers.instanceOf;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.Mockito.when;
+
+class MyClipboardTest {
+
+    @Mock
+    private SystemUtils systemUtilsMock;
+
+    private MyClipboard sut;
+
+    @BeforeEach
+    void setUp() {
+        MockitoAnnotations.openMocks(this);
+        MyClipboard.setSystemUtils(systemUtilsMock);
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideArgumentsForSuccessfullyRetrievingCorrectClipboardListenerForSystem")
+    void successfullyRetrieveCorrectClipboardListenerForSystem(boolean isMac, boolean isWindows, boolean isUnix, Class<?> expectedListener) throws UnsupportedSystemException {
+        when(systemUtilsMock.isMac()).thenReturn(isMac);
+        when(systemUtilsMock.isWindows()).thenReturn(isWindows);
+        when(systemUtilsMock.isUnix()).thenReturn(isUnix);
+
+        MyClipboard actualMyClipboard = MyClipboard.getSystemClipboard();
+
+        assertThat(actualMyClipboard.getClipboardListener(), instanceOf(expectedListener));
+    }
+
+    @Test
+    void failToRetrieveCorrectClipboardListenerForSystem() {
+        String expectedOperatingSystem = "unknown";
+        System.setProperty("os.name", expectedOperatingSystem);
+        Throwable expectedException = new UnsupportedSystemException("Your Operating System: '" + System.getProperty("os.name") + "' is not supported");
+
+        when(systemUtilsMock.isMac()).thenReturn(false);
+        when(systemUtilsMock.isWindows()).thenReturn(false);
+        when(systemUtilsMock.isUnix()).thenReturn(false);
+
+        Throwable actualException = assertThrows(UnsupportedSystemException.class, MyClipboard::getSystemClipboard);
+
+        assertThat(actualException, instanceOf(expectedException.getClass()));
+        assertThat(actualException.getMessage(), is(expectedException.getMessage()));
+    }
+
+    static Stream<Arguments> provideArgumentsForSuccessfullyRetrievingCorrectClipboardListenerForSystem() {
+        return Stream.of(
+                Arguments.of(false, true, false, WindowsOrUnixClipboardListener.class),
+                Arguments.of(false, false, true, WindowsOrUnixClipboardListener.class),
+                Arguments.of(true, false, false, MacClipboardListener.class)
+        );
+    }
+}