Add example test for a debounce function

SampleProjects/TestSomething/test/debounce.cpp

@@ -0,0 +1,153 @@
+#include <ArduinoUnitTests.h>
+#include <Arduino.h>
+
+// the setup for the debouncing function that we will test
+// via https://www.arduino.cc/en/Tutorial/BuiltInExamples/Debounce
+//  ... condensed for brevity
+//
+// pretend that sketch is a library function that is run on every loop
+// e.g.
+//   void loop() { onLoop(); }
+//
+const int buttonPin = 2;          // the number of the pushbutton pin
+const int ledPin = 13;            // the number of the LED pin
+const long debounceDelay = 50;    // debounce time; increase if the output flickers
+int ledState;                     // current state of the output pin
+int buttonState;                  // current reading from the input pin
+int lastButtonState;              // previous reading from the input pin
+unsigned long lastDebounceTime;   // last time the output pin was toggled
+
+void onLoop() {
+  // read state, record time if the input flipped
+  int reading = digitalRead(buttonPin);
+  if (reading != lastButtonState) lastDebounceTime = millis();
+
+  if ((millis() - lastDebounceTime) > debounceDelay) {
+    if (reading != buttonState) {
+      buttonState = reading;
+      if (buttonState == HIGH) ledState = !ledState;
+      digitalWrite(ledPin, ledState);
+    }
+  }
+
+  lastButtonState = reading;
+}
+
+
+/////////// Unit tests
+//
+// This isn't an exhaustive test of states and transitions. Consider permutations of the following variables:
+//   - ledState
+//   - buttonState
+//   - lastButtonState
+//   - the actual digital value on the input
+//   - the current time relative to the last debounce time
+//
+// But we will test a few bounces: 0 transitions, 1 transition, and 3 transitions.
+// The general pattern is
+//  0. set the initial software state
+//  1. set the hardware state (including clock)
+//  2. call the library function
+//  3. validate software state and hardware output state against expectations
+// repeat steps 1-3 as necessary for changing inputs
+
+// Declare state and reset it for each test
+GodmodeState* state = GODMODE();
+unittest_setup() {
+  state->reset();
+}
+
+unittest(nothing_happens_if_button_isnt_pressed) {
+  // initial library state
+  ledState         = LOW;
+  buttonState      = LOW;
+  lastButtonState  = LOW;
+  lastDebounceTime = 0;
+
+  state->micros    = 0;
+  assertEqual(LOW, state->digitalPin[buttonPin]);           // initial input low (default)
+  assertEqual(1, state->digitalPin[ledPin].historySize());  // initial output history has 1 entry so far (low)
+
+  onLoop();
+  assertEqual(LOW, state->digitalPin[ledPin]);      // nothing has changed on the hardware end
+  assertEqual(LOW, lastButtonState);
+  assertEqual(0, state->micros);                    // remember, only we can advance the clock
+  assertEqual(0, lastDebounceTime);
+
+  state->micros = 50001;                            // advance the clock
+  onLoop();
+  assertEqual(LOW, state->digitalPin[ledPin]);      // still no change
+  assertEqual(LOW, lastButtonState);
+  assertEqual(0, lastDebounceTime);
+}
+
+unittest(perfectly_clean_low_to_high) {
+  ledState                     = LOW;
+  buttonState                  = LOW;
+  lastButtonState              = LOW;
+  lastDebounceTime             = 0;
+  state->micros                = 25000;
+  state->digitalPin[buttonPin] = HIGH;                     // set initial button entry to HIGH
+
+  onLoop();
+  assertEqual(LOW, state->digitalPin[ledPin]);
+  assertEqual(HIGH, lastButtonState);
+  assertEqual(LOW, ledState);
+  assertEqual(25, lastDebounceTime);
+  assertEqual(1, state->digitalPin[ledPin].historySize()); //  no change in output
+
+  // actual boundary case
+  state->micros = 75999;
+  onLoop();
+  assertEqual(LOW, state->digitalPin[ledPin]);
+  assertEqual(HIGH, lastButtonState);
+  assertEqual(LOW, ledState);
+  assertEqual(25, lastDebounceTime);
+  assertEqual(1, state->digitalPin[ledPin].historySize()); //  no change in output
+
+  // actual boundary case for exact timing
+  state->micros = 76000;
+  onLoop();
+  assertEqual(HIGH, state->digitalPin[ledPin]);
+  assertEqual(HIGH, lastButtonState);
+  assertEqual(HIGH, ledState);
+  assertEqual(25, lastDebounceTime);
+  assertEqual(2, state->digitalPin[ledPin].historySize()); //  output was written
+}
+
+unittest(bounce_low_to_high) {
+  ledState                     = LOW;
+  buttonState                  = LOW;
+  lastButtonState              = LOW;
+  lastDebounceTime             = 0;
+
+  state->micros                = 25000;
+  state->digitalPin[buttonPin] = HIGH;                     // set initial button entry to HIGH
+  onLoop();
+  assertEqual(25, lastDebounceTime);                       // debounce time has reset
+  assertEqual(LOW, state->digitalPin[ledPin]);             // no change in output
+  assertEqual(HIGH, lastButtonState);
+
+  state->micros                = 50000;
+  state->digitalPin[buttonPin] = LOW;                      // bounce button LOW
+  onLoop();
+  assertEqual(50, lastDebounceTime);                       // debounce time has reset
+  assertEqual(LOW, state->digitalPin[ledPin]);             // no change in LED output
+  assertEqual(LOW, lastButtonState);
+
+  state->micros                = 75000;
+  state->digitalPin[buttonPin] = HIGH;                     // bounce button HIGH
+  onLoop();
+  assertEqual(75, lastDebounceTime);                       // debounce time is again reset
+  assertEqual(LOW, state->digitalPin[ledPin]);             // still no change in LED output
+  assertEqual(HIGH, lastButtonState);
+
+  state->micros                = 126000;                   // actual boundary case, time elapsed
+  state->digitalPin[buttonPin] = HIGH;
+  onLoop();
+  assertEqual(75, lastDebounceTime);                       // no additional bounce happened
+  assertEqual(HIGH, state->digitalPin[ledPin]);            // therefore the LED turns on
+  assertEqual(2, state->digitalPin[ledPin].historySize()); // digital output was written only once
+}
+
+unittest_main()