[examples] Add unit testing infrastructure (#4646)

wpilibjExamples/src/test/java/edu/wpi/first/wpilibj/examples/unittest/subsystems/IntakeTest.java

@@ -0,0 +1,70 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+package edu.wpi.first.wpilibj.examples.unittest.subsystems;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import edu.wpi.first.hal.HAL;
+import edu.wpi.first.wpilibj.DoubleSolenoid;
+import edu.wpi.first.wpilibj.PneumaticsModuleType;
+import edu.wpi.first.wpilibj.examples.unittest.Constants.IntakeConstants;
+import edu.wpi.first.wpilibj.simulation.DoubleSolenoidSim;
+import edu.wpi.first.wpilibj.simulation.PWMSim;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class IntakeTest {
+  static final double DELTA = 1e-2; // acceptable deviation range
+  Intake m_intake;
+  PWMSim m_simMotor;
+  DoubleSolenoidSim m_simPiston;
+
+  @BeforeEach // this method will run before each test
+  void setup() {
+    assert HAL.initialize(500, 0); // initialize the HAL, crash if failed
+    m_intake = new Intake(); // create our intake
+    m_simMotor =
+        new PWMSim(IntakeConstants.kMotorPort); // create our simulation PWM motor controller
+    m_simPiston =
+        new DoubleSolenoidSim(
+            PneumaticsModuleType.CTREPCM,
+            IntakeConstants.kPistonFwdChannel,
+            IntakeConstants.kPistonRevChannel); // create our simulation solenoid
+  }
+
+  @SuppressWarnings("PMD.SignatureDeclareThrowsException")
+  @AfterEach // this method will run after each test
+  void shutdown() throws Exception {
+    m_intake.close(); // destroy our intake object
+  }
+
+  @Test // marks this method as a test
+  void doesntWorkWhenClosed() {
+    m_intake.retract(); // close the intake
+    m_intake.activate(0.5); // try to activate the motor
+    assertEquals(
+        0.0, m_simMotor.getSpeed(), DELTA); // make sure that the value set to the motor is 0
+  }
+
+  @Test
+  void worksWhenOpen() {
+    m_intake.deploy();
+    m_intake.activate(0.5);
+    assertEquals(0.5, m_simMotor.getSpeed(), DELTA);
+  }
+
+  @Test
+  void retractTest() {
+    m_intake.retract();
+    assertEquals(DoubleSolenoid.Value.kReverse, m_simPiston.get());
+  }
+
+  @Test
+  void deployTest() {
+    m_intake.deploy();
+    assertEquals(DoubleSolenoid.Value.kForward, m_simPiston.get());
+  }
+}