TDD For Android -- DroidCon Torino 2015

TDD for ANDROID

Matteo Vaccari !

matteo.vaccari@thoughtworks.com @xpmatteo

WHY TEST?

Deliver software faster

Deliver valuable software faster

Deliver valuable software faster,

sustainably

WHY TEST?

WHY TEST?

• Tests help me design my code

• Tests check that my code works

the developer perspective

the tester perspective

Some tests are less useful than others…

Bureaucratic tests

1. Think a line of production code

2. Write a test that proves that the line of code exists

3. Write the line of code

4. .

Useful tests

1. Think a behaviour that I would like to have

2. Write a test that proves that the behaviour exists

3. Experiment ways to pass the test

4. $$$!………… Value !!!

What is TDD?

From Growing Object-Oriented Software by Nat Pryce and Steve Freeman

Why is it difficult to TDD on Android?

The TDD cycle should be fast!

Value adding ? Or waste?

fixing Gradle builds is waste

and is not funHow do you tell if an activity is value adding or waste? Imagine doing that activity all the time… how does it feel? What would the customer say if you do it all the time?

Programming Skill > Fancy

Libraries

Model-View Separation

Model-View Separation

Model-View Separation

App!(Android)

Core!(Pure Java)

Acceptance!Test

Unit!Test

From Growing Object-Oriented Software by Nat Pryce and Steve Freeman

Unit Doctor Acceptance Tests

public void testInchesToCentimeters() throws Throwable { givenTheUserSelectedConversion("in", "cm"); whenTheUserEnters("2"); thenTheResultIs("2.00 in = 5.08 cm"); }! public void testFahrenheitToCelsius() throws Throwable { givenTheUserSelectedConversion("F", "C"); whenTheUserEnters("50"); thenTheResultIs("50.00 F = 10.00 C"); }! public void testUnknownUnits() throws Throwable { givenTheUserSelectedConversion("ABC", "XYZ"); thenTheResultIs("I don't know how to convert this"); }

public class UnitConversionAcceptanceTest extends ActivityInstrumentationTestCase2<MainActivity> { public UnitConversionAcceptanceTest() { super(MainActivity.class); }! public void testInchesToCentimeters() throws Throwable { givenTheUserSelectedConversion("in", "cm"); whenTheUserEnters("2"); thenTheResultIs("2.00 in = 5.08 cm"); }! private void givenTheUserSelectedConversion(String fromUnit, String toUnit) throws Throwable { setText(R.id.fromUnit, fromUnit); setText(R.id.toUnit, toUnit); }! private void whenTheUserEnters(String inputNumber) throws Throwable { setText(R.id.inputNumber, inputNumber); }! private void thenTheResultIs(String expectedResult) { assertEquals(expectedResult, getField(R.id.result).getText()); }! private void setText(final int id, final String text) throws Throwable { final TextView field = getField(id); runTestOnUiThread(new Runnable() { @Override

}! private void givenTheUserSelectedConversion(String fromUnit, String toUnit) throws Throwable { setText(R.id.fromUnit, fromUnit); setText(R.id.toUnit, toUnit); }! private void whenTheUserEnters(String inputNumber) throws Throwable { setText(R.id.inputNumber, inputNumber); }! private void thenTheResultIs(String expectedResult) { assertEquals(expectedResult, getField(R.id.result).getText()); }! private void setText(final int id, final String text) throws Throwable { final TextView field = getField(id); runTestOnUiThread(new Runnable() { @Override public void run() { field.setText(text); } }); }! private TextView getField(int id) { return (TextView) getActivity().findViewById(id); }}

The simplest thingpublic class MyActivity extends Activity implements View.OnKeyListener { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_my);! getEditText(R.id.inputNumber).setOnKeyListener(this); getEditText(R.id.fromUnit).setOnKeyListener(this); getEditText(R.id.toUnit).setOnKeyListener(this); }! @Override public boolean onKey(View v, int keyCode, KeyEvent event) { String input = getEditText(R.id.inputNumber).getText(); String fromUnit = getEditText(R.id.fromUnit).getText(); String toUnit = getEditText(R.id.toUnit).getText(); getEditText(R.id.result).setText(" Hello! " + input + fromUnit + toUnit); return false; }! private EditText getEditText(int id) { return (EditText) findViewById(id); }!

The simplest thingpublic class MyActivity extends Activity implements View.OnKeyListener { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_my);! getEditText(R.id.inputNumber).setOnKeyListener(this); getEditText(R.id.fromUnit).setOnKeyListener(this); getEditText(R.id.toUnit).setOnKeyListener(this); }! @Override public boolean onKey(View v, int keyCode, KeyEvent event) { String input = getEditText(R.id.inputNumber).getText(); String fromUnit = getEditText(R.id.fromUnit).getText(); String toUnit = getEditText(R.id.toUnit).getText(); getEditText(R.id.result).setText(new UnitDoctor().convert(input, fromUnit, toUnit)); return false; }! private EditText getEditText(int id) { return (EditText) findViewById(id); }!

Very easy to testpublic class UnitDoctorTest {! @Test public void convertsInchesToCentimeters() { UnitDoctor unitDoctor = new UnitDoctor(); assertEquals("2.54", unitDoctor.convert("1", "in", "cm")); }!}

Yes yes… but my app interacts heavily with

Android widgets!

Presenter-Firstpublic class UnitDoctorTest { @Rule public JUnitRuleMockery context = new JUnitRuleMockery();! UnitDoctorView view = context.mock(UnitDoctorView.class); UnitDoctor unitDoctor = new UnitDoctor(view);! @Test public void convertInchesToCm() throws Exception { context.checking(new Expectations() {{ allowing(view).inputNumber(); will(returnValue(1.0)); allowing(view).fromUnit(); will(returnValue("in")); allowing(view).toUnit(); will(returnValue("cm")); oneOf(view).showResult(2.54); }});! unitDoctor.convert(); }! @Test

What are mocks good for?

Mocking Android APIs?

Designing interfaces ✅

Discover the “view” interface

public interface UnitDoctorView { double inputNumber();! String fromUnit();! String toUnit();! void showResult(double result); }

Presenter-Firstpublic class UnitDoctorTest { @Rule public JUnitRuleMockery context = new JUnitRuleMockery();! UnitDoctorView view = context.mock(UnitDoctorView.class); UnitDoctor unitDoctor = new UnitDoctor(view);! @Test public void convertInchesToCm() throws Exception { context.checking(new Expectations() {{ allowing(view).inputNumber(); will(returnValue(1.0)); allowing(view).fromUnit(); will(returnValue("in")); allowing(view).toUnit(); will(returnValue("cm")); oneOf(view).showResult(2.54); }});! unitDoctor.convert(); }! @Test

Discover the “view” interface

@Test public void showsConversionNotSupported() throws Exception { context.checking(new Expectations() {{ allowing(view).inputNumber(); will(returnValue(anyDouble())); allowing(view).fromUnit(); will(returnValue("XYZ")); allowing(view).toUnit(); will(returnValue("ABC")); oneOf(view).showConversionNotSupported(); }});! unitDoctor.convert(); }

Discover the “view” interface

public interface UnitDoctorView { double inputNumber();! String fromUnit();! String toUnit();! void showResult(double result);! void showConversionNotSupported(); }

Implement the “view” interface

• In the Activity class

• In an Android View class

• In a new POJO class

Yes, yes, yes… but my app interacts heavily with

Android APIs!

Acceptance tests• Single touch. Dragging the finger should produce

a colored trail that fades to nothing

• Two touches. Dragging two fingers should produce two decaying trails

• Multi-touch dashes. Draw a pattern like —— —-— —-————————————

Start with a spike!

Start with a spike! public class FingerView extends View { @Override protected void onDraw(Canvas canvas) { Paint paint = new Paint(); paint.setColor(Color.BLUE); paint.setStrokeWidth(3); paint.setStyle(Paint.Style.STROKE); canvas.canvas.drawLine(100, 100, 200, 200, paint); } }

More spike!

More spike!public class MyView extends View { List<Point> points = new ArrayList<Point>();! @Override protected void onDraw(Canvas canvas) { Paint paint = new Paint(); paint.setColor(Color.BLUE); paint.setStrokeWidth(3); for (int i=1; i<points.size(); i++) { Point from = points.get(i-1); Point to = points.get(i); canvas.drawLine(from.x, from.y, to.x, to.y, paint); } }! @Override public boolean onTouchEvent(MotionEvent event) { int action = event.getActionMasked(); if (action == MotionEvent.ACTION_DOWN) { points.clear(); points.add(new Point((int) event.getX(), (int) event.getY())); } else if (action == MotionEvent.ACTION_MOVE) { points.add(new Point((int) event.getX(), (int) event.getY())); } invalidate(); return true; }}

FairyFingersCore

AndroidMotionEvent

AndroidCanvas

FairyFingersView

onDraw(Canvas) { ... }

onTouchEvent(MotionEvent) { ... }

Android dependent

Pure Java

FairyFingersCore

AndroidMotionEvent

AndroidCanvas

FairyFingersView

onDraw(Canvas) { ... }

onTouchEvent(MotionEvent) { ... }

CoreCanvas

CoreMotionEvent Android dependent

Pure Java

Model-View Separation

App!(Android)

Core!(Pure Java)

Acceptance!Test

Unit!Test

! public interface CoreCanvas { void drawLine(float startX, float startY, float stopX, float stopY); }!!!! @Override protected void onDraw(final Canvas canvas) { paint.setColor(Color.BLUE); paint.setStrokeWidth(4); for (Line line : core.lines()) { line.drawOn(new CoreCanvas() { @Override public void drawLine(float startX, float startY, float stopX, float stopY) { canvas.drawLine(startX, startY, stopX, stopY, paint); } }); } }

public interface CoreMotionEvent { int getAction(); int getPointerCount(); int getPointerId(int pointerIndex); void getPointerCoords(int pointerIndex, CorePoint outPointerCoords); }

// Constants copied from android.view.MotionEvent static final int ACTION_DOWN = 0; static final int ACTION_UP = 1; static final int ACTION_MOVE = 2; static final int ACTION_CANCEL = 3; static final int ACTION_POINTER_DOWN = 5; static final int ACTION_POINTER_UP = 6;

@Override public boolean onTouchEvent(final MotionEvent event) { core.onTouch(new CoreMotionEvent() { @Override public int getPointerCount() { return event.getPointerCount(); }! @Override public int getPointerId(int pointerIndex) { return event.getPointerId(pointerIndex); }! @Override public void getPointerCoords(int pointerIndex, CorePoint outPointerCoords) { MotionEvent.PointerCoords coords = new MotionEvent.PointerCoords(); event.getPointerCoords(pointerIndex, coords); outPointerCoords.x = coords.x; outPointerCoords.y = coords.y; }! @Override public int getActionIndex() { return event.getActionIndex(); }! @Override public int getAction() { return event.getAction();

!public class FairyFingersCoreTest { FairyFingersCore core = new FairyFingersCore();! @Test public void noLinesAtStart() throws Exception { assertEquals(0, core.lines().size()); }! @Test public void startOneLine() throws Exception { core.onTouch(down(10.0f, 100.0f));! assertEquals(1, core.lines().size()); assertEquals("(10.0,100.0)", core.lines(0).toString()); }! @Test public void oneLineDownMove() throws Exception { core.onTouch(down(10.0f, 110.0f)); core.onTouch(move(20.0f, 120.0f)); core.onTouch(move(30.0f, 130.0f));! assertEquals("(10.0,110.0)->(20.0,120.0)->(30.0,130.0)", core.lines(0).toString()); }! @Test public void oneLineDownMoveUp() throws Exception { core.onTouch(down(10.0f, 100.0f)); core.onTouch(move(20.9f, 120.0f)); core.onTouch(move(30.0f, 130.0f));

TDD!

Programming Skill > Fancy

Libraries

Value adding ? Or waste?

Deliver valuable software faster,

sustainably

References• TDD For Android book (unfinished!)

leanpub.com/tddforandroid!

• Source code for examples: github.com/xpmatteo!

• Learn OOP and TDD well: Growing Object-Oriented Software, Nat Pryce and Steve Freeman TDD By Example, Kent Beck Applying UML and Patterns, Craig Larman

Credits• Carlo Bellettini was my sparring partner for this work

• The motto “Deliver valuable software faster, sustainably” is my elaboration on Dan North’s “The goal of software delivery is to minimise the lead time to business impact. Everything else is detail.” I advise to attend one of Dan’s seminars. They are illuminating.

• The “Fairy Fingers” idea is from “Ribbons” by Carlo Pescio (www.aspectroid.com)

• The “gravity test” example is derived from a presentation by Diego Torres Milano

Questions?

THANK YOU