Add utility class tests (#871)

Checks for classes that only have static methods.

wpilibj/src/main/java/edu/wpi/first/wpilibj/RobotController.java

@@ -18,6 +18,7 @@ import edu.wpi.first.wpilibj.hal.PowerJNI;
  */
 public final class RobotController {
   private RobotController() {
+    throw new UnsupportedOperationException("This is a utility class!");
   }
 
   /**

wpilibj/src/main/java/edu/wpi/first/wpilibj/livewindow/LiveWindow.java

@@ -45,6 +45,10 @@ public class LiveWindow {
   private static boolean liveWindowEnabled = false;
   private static boolean telemetryEnabled = true;
 
+  private LiveWindow() {
+    throw new UnsupportedOperationException("This is a utility class!");
+  }
+
   public static synchronized boolean isEnabled() {
     return liveWindowEnabled;
   }

wpilibj/src/main/java/edu/wpi/first/wpilibj/smartdashboard/SmartDashboard.java

@@ -51,6 +51,10 @@ public class SmartDashboard {
     HLUsageReporting.reportSmartDashboard();
   }
 
+  private SmartDashboard() {
+    throw new UnsupportedOperationException("This is a utility class!");
+  }
+
   /**
    * Maps the specified key to the specified value in this table. The key can not be null. The value
    * can be retrieved by calling the get method with a key that is equal to the original key.

wpilibj/src/test/java/edu/wpi/first/wpilibj/RobotControllerTest.java

@@ -0,0 +1,14 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+package edu.wpi.first.wpilibj;
+
+public class RobotControllerTest extends UtilityClassTest {
+  public RobotControllerTest() {
+    super(RobotController.class);
+  }
+}

wpilibj/src/test/java/edu/wpi/first/wpilibj/UtilityClassTest.java

@@ -0,0 +1,73 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+package edu.wpi.first.wpilibj;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.fail;
+
+@SuppressWarnings("PMD.AbstractClassWithoutAbstractMethod")
+public abstract class UtilityClassTest {
+  @Before
+  public void setup() {
+    UnitTestUtility.setupMockBase();
+  }
+
+  private final Class m_clazz;
+
+  protected UtilityClassTest(Class clazz) {
+    m_clazz = clazz;
+  }
+
+  @Test
+  public void testSingleConstructor() {
+    assertEquals("More than one constructor defined", 1,
+        m_clazz.getDeclaredConstructors().length);
+  }
+
+  @Test
+  public void testConstructorPrivate() {
+    Constructor constructor = m_clazz.getDeclaredConstructors()[0];
+
+    assertFalse("Constructor is not private", constructor.isAccessible());
+  }
+
+  @Test(expected = InvocationTargetException.class)
+  public void testConstructorReflection() throws Throwable {
+    Constructor constructor = m_clazz.getDeclaredConstructors()[0];
+    constructor.setAccessible(true);
+    constructor.newInstance();
+  }
+
+  @Test
+  public void testPublicMethodsStatic() {
+    List<String> failures = new ArrayList<>();
+    for (Method method : m_clazz.getDeclaredMethods()) {
+      int modifiers = method.getModifiers();
+      if (Modifier.isPublic(modifiers) && !Modifier.isStatic(modifiers)) {
+        failures.add(method.toString());
+      }
+    }
+
+    if (!failures.isEmpty()) {
+      fail("Found public methods that are not static: "
+          + Arrays.toString(failures.toArray()));
+    }
+  }
+}

wpilibj/src/test/java/edu/wpi/first/wpilibj/livewindow/LiveWindowTest.java

@@ -0,0 +1,16 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+package edu.wpi.first.wpilibj.livewindow;
+
+import edu.wpi.first.wpilibj.UtilityClassTest;
+
+public class LiveWindowTest extends UtilityClassTest {
+  public LiveWindowTest() {
+    super(LiveWindow.class);
+  }
+}

wpilibj/src/test/java/edu/wpi/first/wpilibj/smartdashboard/SmartDashboardTest.java

@@ -0,0 +1,16 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+package edu.wpi.first.wpilibj.smartdashboard;
+
+import edu.wpi.first.wpilibj.UtilityClassTest;
+
+public class SmartDashboardTest extends UtilityClassTest {
+  public SmartDashboardTest() {
+    super(SmartDashboard.class);
+  }
+}