Added a conditional command that chooses 1 of 2 commands (#435)

Tests and documentation for ConditionalCommand were also added. This is a fixed version of #9, so it doesn't support lambdas.

Closes #9

wpilibj/src/test/java/edu/wpi/first/wpilibj/command/ConditionalCommandTest.java

@@ -0,0 +1,65 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2017. 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.command;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class ConditionalCommandTest extends AbstractCommandTest {
+  MockConditionalCommand m_command;
+  MockCommand m_onTrue;
+  MockCommand m_onFalse;
+  Boolean m_condition;
+
+  @Before
+  public void initCommands() {
+    m_onTrue = new MockCommand();
+    m_onFalse = new MockCommand();
+    m_command = new MockConditionalCommand(m_onTrue, m_onFalse);
+  }
+
+  @Test
+  public void testOnTrue() {
+    m_command.setCondition(true);
+
+    Scheduler.getInstance().add(m_command);
+    assertCommandState(m_onTrue, 0, 0, 0, 0, 0);
+    Scheduler.getInstance().run();  // init command and select m_onTrue
+    assertCommandState(m_onTrue, 0, 0, 0, 0, 0);
+    Scheduler.getInstance().run();  // init m_onTrue
+    assertCommandState(m_onTrue, 0, 0, 0, 0, 0);
+    Scheduler.getInstance().run();
+    assertCommandState(m_onTrue, 1, 1, 2, 0, 0);
+    Scheduler.getInstance().run();
+    assertCommandState(m_onTrue, 1, 2, 4, 0, 0);
+
+    assertTrue("Did not initialize the true command", m_onTrue.getInitializeCount() > 0);
+    assertTrue("Initialized the false command", m_onFalse.getInitializeCount() == 0);
+  }
+
+  @Test
+  public void testOnFalse() {
+    m_command.setCondition(false);
+
+    Scheduler.getInstance().add(m_command);
+    assertCommandState(m_onFalse, 0, 0, 0, 0, 0);
+    Scheduler.getInstance().run();  // init command and select m_onFalse
+    assertCommandState(m_onFalse, 0, 0, 0, 0, 0);
+    Scheduler.getInstance().run();  // init m_onFalse
+    assertCommandState(m_onFalse, 0, 0, 0, 0, 0);
+    Scheduler.getInstance().run();
+    assertCommandState(m_onFalse, 1, 1, 2, 0, 0);
+    Scheduler.getInstance().run();
+    assertCommandState(m_onFalse, 1, 2, 4, 0, 0);
+
+    assertTrue("Did not initialize the false command", m_onFalse.getInitializeCount() > 0);
+    assertTrue("Initialized the true command", m_onTrue.getInitializeCount() == 0);
+  }
+}

wpilibj/src/test/java/edu/wpi/first/wpilibj/command/MockConditionalCommand.java

@@ -0,0 +1,25 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2017. 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.command;
+
+public class MockConditionalCommand extends ConditionalCommand {
+  private boolean m_condition = false;
+
+  public MockConditionalCommand(MockCommand onTrue, MockCommand onFalse) {
+    super(onTrue, onFalse);
+  }
+
+  @Override
+  protected boolean condition() {
+    return m_condition;
+  }
+
+  public void setCondition(boolean condition) {
+    this.m_condition = condition;
+  }
+}