Add more tests in AdjacentFreePortFinderTest (#554)

* Add test to ensure it finds last two ports in range when all others
are in use
* Add test to ensure it throws exception when all but last port in range
are in use

src/test/java/org/kiwiproject/dropwizard/util/startup/AdjacentFreePortFinderTest.java

@@ -6,6 +6,7 @@
 import static org.junit.jupiter.api.Assertions.assertAll;
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
@@ -110,6 +111,70 @@ void shouldFindNextAdjacentApplicationAndAdminPorts_WhenSomeAreInUse() {
         verify(checker, times(17)).isPortAvailable(anyInt());
     }
 
+    @Test
+    void shouldFindLastTwoPortsInRange_WhenAllOthersAreInUse() {
+        var checker = mock(LocalPortChecker.class);
+        var portFinder = new AdjacentFreePortFinder(checker);
+
+        when(checker.isPortAvailable(anyInt()))
+                .thenReturn(false)  // 9000
+                .thenReturn(false)  // 9001
+                .thenReturn(false)  // 9002
+                .thenReturn(false)  // 9003
+                .thenReturn(true)   // 9004
+                .thenReturn(true);  // 9005
+
+        var minPortNumber = 9_000;
+        var maxPortNumber = 9_005;
+
+        var servicePorts = portFinder.find(new AllowablePortRange(minPortNumber, maxPortNumber));
+
+        assertAll(
+                () -> assertThat(servicePorts.applicationPort()).isEqualTo(9_004),
+                () -> assertThat(servicePorts.adminPort()).isEqualTo(9_005)
+        );
+
+        verify(checker).isPortAvailable(9_000);
+        verify(checker).isPortAvailable(9_001);
+        verify(checker).isPortAvailable(9_002);
+        verify(checker).isPortAvailable(9_003);
+        verify(checker).isPortAvailable(9_004);
+        verify(checker).isPortAvailable(9_005);
+        verifyNoMoreInteractions(checker);
+    }
+
+    @Test
+    void shouldThrowNoAvailablePortException_WhenAllButLastPortAreInUse() {
+        var checker = mock(LocalPortChecker.class);
+        var portFinder = new AdjacentFreePortFinder(checker);
+
+        when(checker.isPortAvailable(anyInt()))
+                .thenReturn(false)  // 9000
+                .thenReturn(false)  // 9001
+                .thenReturn(false)  // 9002
+                .thenReturn(false)  // 9003
+                .thenReturn(false)  // 9004
+                .thenReturn(true);  // 9005
+
+        var minPortNumber = 9_000;
+        var maxPortNumber = 9_005;
+
+        var portRange = new AllowablePortRange(minPortNumber, maxPortNumber);
+
+        assertThatExceptionOfType(NoAvailablePortException.class)
+                .isThrownBy(() -> portFinder.find(portRange))
+                .withMessage("Could not find two adjacent open ports between %d and %d",
+                        minPortNumber, maxPortNumber);
+
+        verify(checker).isPortAvailable(9_000);
+        verify(checker).isPortAvailable(9_001);
+        verify(checker).isPortAvailable(9_002);
+        verify(checker).isPortAvailable(9_003);
+        verify(checker).isPortAvailable(9_004);
+        verify(checker, never()).isPortAvailable(9_005);
+        verifyNoMoreInteractions(checker);
+    }
+
     @Test
     void shouldThrowNoAvailablePortException_WhenNoPortsCanBeFound() {
         var checker = mock(LocalPortChecker.class);
@@ -126,6 +191,7 @@ void shouldThrowNoAvailablePortException_WhenNoPortsCanBeFound() {
                 .withMessage("Could not find two adjacent open ports between %d and %d",
                         minPortNumber, maxPortNumber);
 
-        verify(checker, times(portRange.getNumPortsInRange() - 1)).isPortAvailable(anyInt());
+        int expectedNumberOfInvocations = portRange.getNumPortsInRange() - 1;
+        verify(checker, times(expectedNumberOfInvocations)).isPortAvailable(anyInt());
     }
 }