Table of Contents
Introduction to Testing and Debugging
1.1 Why Testing and Debugging Matter
1.2 Types of Testing in Android Development
1.3 Overview of Tools and Techniques
Unit Testing with JUnit
2.1 What is Unit Testing?
2.2 Setting Up JUnit in Android Studio
2.3 Writing Your First Unit Test
2.4 Real-Life Example: Testing a Shopping Cart Calculator
2.5 Best Practices for Unit Testing
2.6 Exception Handling in Unit Tests
2.7 Pros, Cons, and Alternatives
UI Testing with Espresso
3.1 Introduction to UI Testing
3.2 Setting Up Espresso in Android Studio
3.3 Writing UI Tests with Espresso
3.4 Real-Life Example: Testing a Login Screen
3.5 Best Practices for UI Testing
3.6 Exception Handling in UI Tests
3.7 Pros, Cons, and Alternatives
Debugging Tools in Android Studio
4.1 Overview of Debugging Tools
4.2 Using Breakpoints and Watches
4.3 Analyzing Stack Traces
4.4 Real-Life Example: Debugging a Crash in a Food Delivery App
4.5 Best Practices for Debugging
4.6 Exception Handling During Debugging
4.7 Pros, Cons, and Alternatives
Logging and Error Tracking
5.1 Importance of Logging
5.2 Implementing Logging in Android
5.3 Using Third-Party Error Tracking Tools
5.4 Real-Life Example: Tracking Errors in a Fitness App
5.5 Best Practices for Logging
5.6 Exception Handling in Logging
5.7 Pros, Cons, and Alternatives
Performance Optimization Techniques
6.1 Why Optimize App Performance?
6.2 Profiling Tools in Android Studio
6.3 Optimizing CPU, Memory, and Network Usage
6.4 Real-Life Example: Optimizing a Social Media App
6.5 Best Practices for Performance Optimization
6.6 Exception Handling in Optimization
6.7 Pros, Cons, and Alternatives
Practical Exercise: Building and Testing an App
7.1 Project Setup: A To-Do List App
7.2 Adding Unit Tests
7.3 Adding UI Tests
7.4 Debugging a Performance Issue
7.5 Implementing Logging
7.6 Optimizing the App
Conclusion
8.1 Recap of Key Concepts
8.2 Next Steps in Android Development
1. Introduction to Testing and Debugging
1.1 Why Testing and Debugging Matter
Testing and debugging are critical to delivering high-quality Android apps. Testing ensures your app behaves as expected under various conditions, while debugging helps identify and fix issues that cause crashes or poor performance. In real-world scenarios, such as a food delivery app, untested code could lead to incorrect order calculations, while poor debugging could leave users frustrated with crashes.
1.2 Types of Testing in Android Development
Unit Testing: Tests individual components (e.g., functions or classes) in isolation.
UI Testing: Tests user interactions with the app’s interface.
Integration Testing: Tests how components work together.
Manual Testing: Human testers interact with the app to find issues.
Performance Testing: Ensures the app runs efficiently.
1.3 Overview of Tools and Techniques
JUnit: For unit testing.
Espresso: For UI testing.
Android Studio Debugging Tools: Breakpoints, watches, and profilers.
Logging: Using Logcat and third-party tools like Firebase Crashlytics.
Performance Tools: Android Studio’s CPU, memory, and network profilers.
2. Unit Testing with JUnit
2.1 What is Unit Testing?
Unit testing verifies that individual units of code (e.g., methods or classes) work as expected. In Android, JUnit is the go-to framework for unit testing.
2.2 Setting Up JUnit in Android Studio
Add Dependencies: Ensure JUnit is included in your build.gradle file.
dependencies {
testImplementation 'junit:junit:4.13.2'
}Sync Project: Click "Sync Project with Gradle Files" in Android Studio.
Create Test Directory: Ensure the test directory exists under app/src.
2.3 Writing Your First Unit Test
Let’s write a simple test for a method that calculates the total price in a shopping cart.
// ShoppingCart.java
public class ShoppingCart {
public double calculateTotalPrice(double[] prices) {
double total = 0;
for (double price : prices) {
total += price;
}
return total;
}
}// ShoppingCartTest.java (in app/src/test)
import org.junit.Test;
import static org.junit.Assert.assertEquals;
public class ShoppingCartTest {
@Test
public void testCalculateTotalPrice() {
ShoppingCart cart = new ShoppingCart();
double[] prices = {10.0, 20.0, 30.0};
double expected = 60.0;
double actual = cart.calculateTotalPrice(prices);
assertEquals(expected, actual, 0.01);
}
}Run the test by right-clicking the test file in Android Studio and selecting "Run".
2.4 Real-Life Example: Testing a Shopping Cart Calculator
Imagine you’re building an e-commerce app. The ShoppingCart class calculates the total price of items. You need to test edge cases like empty carts or negative prices.
// Enhanced ShoppingCartTest.java
import org.junit.Test;
import static org.junit.Assert.assertEquals;
public class ShoppingCartTest {
@Test
public void testCalculateTotalPrice() {
ShoppingCart cart = new ShoppingCart();
double[] prices = {10.0, 20.0, 30.0};
assertEquals(60.0, cart.calculateTotalPrice(prices), 0.01);
}
@Test
public void testEmptyCart() {
ShoppingCart cart = new ShoppingCart();
double[] prices = {};
assertEquals(0.0, cart.calculateTotalPrice(prices), 0.01);
}
@Test(expected = IllegalArgumentException.class)
public void testNegativePrice() {
ShoppingCart cart = new ShoppingCart();
double[] prices = {10.0, -20.0};
cart.calculateTotalPrice(prices);
}
}Modify ShoppingCart.java to handle the negative price case:
public class ShoppingCart {
public double calculateTotalPrice(double[] prices) {
double total = 0;
for (double price : prices) {
if (price < 0) {
throw new IllegalArgumentException("Price cannot be negative");
}
total += price;
}
return total;
}
}2.5 Best Practices for Unit Testing
Test One Thing at a Time: Each test should focus on a single behavior.
Use Descriptive Test Names: E.g., testEmptyCart instead of test1.
Mock Dependencies: Use libraries like Mockito for mocking.
Run Tests Frequently: Integrate with CI/CD pipelines.
2.6 Exception Handling in Unit Tests
Use @Test(expected = ExceptionType.class) to test for expected exceptions, as shown in the negative price test above.
2.7 Pros, Cons, and Alternatives
Pros:
Fast execution.
Isolates issues in specific code units.
Cons:
Doesn’t test UI or integration.
Requires mocking for complex dependencies.
Alternatives:
Robolectric: For testing Android-specific components.
Mockito: For mocking dependencies.
3. UI Testing with Espresso
3.1 Introduction to UI Testing
UI testing ensures your app’s user interface behaves correctly. Espresso is Android’s preferred framework for UI testing.
3.2 Setting Up Espresso in Android Studio
Add Dependencies:
dependencies {
androidTestImplementation 'androidx.test:runner:1.5.2'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
}Grant Permissions: Ensure your app has necessary permissions for testing.
Create Test Directory: Use androidTest under app/src.
3.3 Writing UI Tests with Espresso
Let’s test a login screen with a username, password, and login button.
<!-- activity_login.xml -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<EditText
android:id="@+id/username"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Username" />
<EditText
android:id="@+id/password"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Password"
android:inputType="textPassword" />
<Button
android:id="@+id/loginButton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Login" />
</LinearLayout>// LoginActivityTest.java (in app/src/androidTest)
import androidx.test.ext.junit.rules.ActivityScenarioRule;
import androidx.test.ext.junit.runners.AndroidJUnit4;
import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;
import static androidx.test.espresso.Espresso.onView;
import static androidx.test.espresso.action.ViewActions.click;
import static androidx.test.espresso.action.ViewActions.typeText;
import static androidx.test.espresso.assertion.ViewAssertions.matches;
import static androidx.test.espresso.matcher.ViewMatchers.withId;
import static androidx.test.espresso.matcher.ViewMatchers.withText;
@RunWith(AndroidJUnit4.class)
public class LoginActivityTest {
@Rule
public ActivityScenarioRule<LoginActivity> activityRule = new ActivityScenarioRule<>(LoginActivity.class);
@Test
public void testLoginSuccess() {
onView(withId(R.id.username)).perform(typeText("user"));
onView(withId(R.id.password)).perform(typeText("pass123"));
onView(withId(R.id.loginButton)).perform(click());
onView(withId(R.id.statusText)).check(matches(withText("Login Successful")));
}
}3.4 Real-Life Example: Testing a Login Screen
For a banking app, you need to test login scenarios, including invalid inputs.
// Enhanced LoginActivityTest.java
@RunWith(AndroidJUnit4.class)
public class LoginActivityTest {
@Rule
public ActivityScenarioRule<LoginActivity> activityRule = new ActivityScenarioRule<>(LoginActivity.class);
@Test
public void testLoginSuccess() {
onView(withId(R.id.username)).perform(typeText("user"));
onView(withId(R.id.password)).perform(typeText("pass123"));
onView(withId(R.id.loginButton)).perform(click());
onView(withId(R.id.statusText)).check(matches(withText("Login Successful")));
}
@Test
public void testInvalidPassword() {
onView(withId(R.id.username)).perform(typeText("user"));
onView(withId(R.id.password)).perform(typeText("wrong"));
onView(withId(R.id.loginButton)).perform(click());
onView(withId(R.id.statusText)).check(matches(withText("Invalid Credentials")));
}
}Modify LoginActivity.java to handle these cases:
public class LoginActivity extends AppCompatActivity {
private EditText username, password;
private TextView statusText;
private Button loginButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
username = findViewById(R.id.username);
password = findViewById(R.id.password);
statusText = findViewById(R.id.statusText);
loginButton = findViewById(R.id.loginButton);
loginButton.setOnClickListener(v -> {
String user = username.getText().toString();
String pass = password.getText().toString();
if (user.equals("user") && pass.equals("pass123")) {
statusText.setText("Login Successful");
} else {
statusText.setText("Invalid Credentials");
}
});
}
}3.5 Best Practices for UI Testing
Test User Flows: Simulate real user interactions.
Use Idling Resources: Handle asynchronous operations.
Keep Tests Focused: Test one UI component at a time.
Run on Multiple Devices: Use emulators or cloud testing services.
3.6 Exception Handling in UI Tests
Handle flaky tests by using IdlingResource for asynchronous tasks like network calls.
3.7 Pros, Cons, and Alternatives
Pros:
Simulates real user interactions.
Integrates with Android Studio.
Cons:
Slower than unit tests.
Requires device/emulator.
Alternatives:
UI Automator: For cross-app testing.
Appium: For cross-platform testing.
4. Debugging Tools in Android Studio
4.1 Overview of Debugging Tools
Android Studio provides:
Breakpoints: Pause execution to inspect code.
Watches: Monitor variable values.
Logcat: View system logs.
Profiler: Analyze CPU, memory, and network usage.
4.2 Using Breakpoints and Watches
Set a Breakpoint: Click the gutter next to a line of code.
Run in Debug Mode: Click the "Debug" button.
Add Watches: Right-click a variable and select "Add to Watches".
4.3 Analyzing Stack Traces
When an app crashes, check the stack trace in Logcat to identify the cause.
4.4 Real-Life Example: Debugging a Crash in a Food Delivery App
Suppose your food delivery app crashes when calculating delivery fees.
// DeliveryCalculator.java
public class DeliveryCalculator {
public double calculateDeliveryFee(Order order) {
return order.getDistance() * 0.5 / order.getItems().size(); // Potential crash if items is empty
}
}Debug the crash:
Set a breakpoint in calculateDeliveryFee.
Run in Debug mode.
Inspect order.getItems().size() to find it’s zero, causing a division-by-zero error.
Fix the code:
public class DeliveryCalculator {
public double calculateDeliveryFee(Order order) {
int itemCount = order.getItems().size();
if (itemCount == 0) {
throw new IllegalArgumentException("Order cannot be empty");
}
return order.getDistance() * 0.5 / itemCount;
}
}4.5 Best Practices for Debugging
Reproduce the Issue: Ensure you can replicate the bug.
Use Conditional Breakpoints: Break only when specific conditions are met.
Log Intermediate States: Add temporary logs to trace execution.
4.6 Exception Handling During Debugging
Wrap risky operations in try-catch blocks to prevent crashes:
try {
double fee = calculateDeliveryFee(order);
} catch (IllegalArgumentException e) {
Log.e("DeliveryCalculator", "Error: " + e.getMessage());
}4.7 Pros, Cons, and Alternatives
Pros:
Precise issue identification.
Integrated with Android Studio.
Cons:
Time-consuming for complex issues.
Requires understanding of app flow.
Alternatives:
Remote Debugging: For devices not connected to your machine.
Third-Party Tools: Like Stetho for network debugging.
5. Logging and Error Tracking
5.1 Importance of Logging
Logging helps track app behavior and diagnose issues in production.
5.2 Implementing Logging in Android
Use Android’s Log class:
import android.util.Log;
public class FitnessActivity {
private static final String TAG = "FitnessActivity";
public void recordWorkout(String workout) {
Log.d(TAG, "Recording workout: " + workout);
}
}5.3 Using Third-Party Error Tracking Tools
Integrate Firebase Crashlytics:
Add Dependency:
dependencies {
implementation 'com.google.firebase:firebase-crashlytics:18.3.5'
}Initialize Crashlytics: Follow Firebase setup instructions.
5.4 Real-Life Example: Tracking Errors in a Fitness App
Track crashes when a user logs a workout with invalid data.
public class FitnessActivity {
private static final String TAG = "FitnessActivity";
public void recordWorkout(String workout) {
try {
if (workout == null || workout.isEmpty()) {
throw new IllegalArgumentException("Workout cannot be empty");
}
Log.d(TAG, "Recording workout: " + workout);
} catch (IllegalArgumentException e) {
Log.e(TAG, "Error: " + e.getMessage());
FirebaseCrashlytics.getInstance().recordException(e);
}
}
}5.5 Best Practices for Logging
Use Appropriate Log Levels: Log.d for debug, Log.e for errors.
Avoid Sensitive Data: Don’t log user information.
Clear Log Messages: Include context for easier debugging.
5.6 Exception Handling in Logging
Always catch and log exceptions to prevent crashes.
5.7 Pros, Cons, and Alternatives
Pros:
Helps diagnose issues in production.
Integrates with analytics platforms.
Cons:
Overhead in large apps.
Privacy concerns with sensitive data.
Alternatives:
Sentry: For advanced error tracking.
Timber: For simplified logging.
6. Performance Optimization Techniques
6.1 Why Optimize App Performance?
Poor performance leads to slow apps, high battery usage, and user frustration.
6.2 Profiling Tools in Android Studio
CPU Profiler: Tracks method execution time.
Memory Profiler: Identifies memory leaks.
Network Profiler: Monitors network requests.
6.3 Optimizing CPU, Memory, and Network Usage
CPU: Avoid heavy computations on the main thread.
Memory: Use WeakReference for large objects.
Network: Cache responses and compress data.
6.4 Real-Life Example: Optimizing a Social Media App
Optimize image loading in a social media feed:
// ImageLoader.java
public class ImageLoader {
public void loadImage(ImageView imageView, String url) {
// Inefficient: Loads full-size image
Bitmap bitmap = BitmapFactory.decodeStream(new URL(url).openStream());
imageView.setImageBitmap(bitmap);
}
}Optimized version using Glide:
// Add Glide dependency
dependencies {
implementation 'com.github.bumptech.glide:glide:4.12.0'
}
// Optimized ImageLoader.java
import com.bumptech.glide.Glide;
public class ImageLoader {
public void loadImage(ImageView imageView, String url) {
Glide.with(imageView.getContext())
.load(url)
.thumbnail(0.25f)
.diskCacheStrategy(DiskCacheStrategy.ALL)
.into(imageView);
}
}6.5 Best Practices for Performance Optimization
Use Background Threads: For heavy tasks.
Profile Regularly: Catch issues early.
Optimize Layouts: Avoid nested layouts.
6.6 Exception Handling in Optimization
Handle network failures gracefully:
try {
loadImage(imageView, url);
} catch (IOException e) {
Log.e("ImageLoader", "Failed to load image: " + e.getMessage());
imageView.setImageResource(R.drawable.placeholder);
}6.7 Pros, Cons, and Alternatives
Pros:
Improves user experience.
Reduces resource usage.
Cons:
Time-consuming to optimize.
May introduce complexity.
Alternatives:
Coil: Alternative to Glide for image loading.
OkHttp: For efficient network requests.
7. Practical Exercise: Building and Testing an App
7.1 Project Setup: A To-Do List App
Create a simple to-do list app with a single activity.
<!-- activity_main.xml -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<EditText
android:id="@+id/taskInput"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Enter task" />
<Button
android:id="@+id/addButton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Add Task" />
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/taskList"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>// MainActivity.java
public class MainActivity extends AppCompatActivity {
private EditText taskInput;
private RecyclerView taskList;
private TaskAdapter adapter;
private List<String> tasks = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
taskInput = findViewById(R.id.taskInput);
taskList = findViewById(R.id.taskList);
taskList.setLayoutManager(new LinearLayoutManager(this));
adapter = new TaskAdapter(tasks);
taskList.setAdapter(adapter);
findViewById(R.id.addButton).setOnClickListener(v -> {
String task = taskInput.getText().toString();
if (!task.isEmpty()) {
tasks.add(task);
adapter.notifyDataSetChanged();
taskInput.setText("");
}
});
}
}// TaskAdapter.java
public class TaskAdapter extends RecyclerView.Adapter<TaskAdapter.ViewHolder> {
private List<String> tasks;
public TaskAdapter(List<String> tasks) {
this.tasks = tasks;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(android.R.layout.simple_list_item_1, parent, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.textView.setText(tasks.get(position));
}
@Override
public int getItemCount() {
return tasks.size();
}
static class ViewHolder extends RecyclerView.ViewHolder {
TextView textView;
ViewHolder(View itemView) {
super(itemView);
textView = itemView.findViewById(android.R.id.text1);
}
}
}7.2 Adding Unit Tests
Test the task addition logic.
// TaskManager.java
public class TaskManager {
private List<String> tasks = new ArrayList<>();
public void addTask(String task) {
if (task == null || task.isEmpty()) {
throw new IllegalArgumentException("Task cannot be empty");
}
tasks.add(task);
}
public List<String> getTasks() {
return tasks;
}
}// TaskManagerTest.java
import org.junit.Test;
import static org.junit.Assert.assertEquals;
public class TaskManagerTest {
@Test
public void testAddTask() {
TaskManager manager = new TaskManager();
manager.addTask("Buy groceries");
assertEquals(1, manager.getTasks().size());
assertEquals("Buy groceries", manager.getTasks().get(0));
}
@Test(expected = IllegalArgumentException.class)
public void testAddEmptyTask() {
TaskManager manager = new TaskManager();
manager.addTask("");
}
}7.3 Adding UI Tests
Test adding a task via the UI.
// MainActivityTest.java
@RunWith(AndroidJUnit4.class)
public class MainActivityTest {
@Rule
public ActivityScenarioRule<MainActivity> activityRule = new ActivityScenarioRule<>(MainActivity.class);
@Test
public void testAddTask() {
onView(withId(R.id.taskInput)).perform(typeText("Buy groceries"));
onView(withId(R.id.addButton)).perform(click());
onView(withText("Buy groceries")).check(matches(isDisplayed()));
}
}7.4 Debugging a Performance Issue
Suppose the RecyclerView lags when adding many tasks. Use the CPU Profiler to identify the issue (e.g., notifyDataSetChanged is inefficient). Optimize by using notifyItemInserted:
// MainActivity.java (optimized)
findViewById(R.id.addButton).setOnClickListener(v -> {
String task = taskInput.getText().toString();
if (!task.isEmpty()) {
tasks.add(task);
adapter.notifyItemInserted(tasks.size() - 1);
taskInput.setText("");
}
});7.5 Implementing Logging
Add logging to track task additions.
// MainActivity.java
public class MainActivity extends AppCompatActivity {
private static final String TAG = "MainActivity";
@Override
protected void onCreate(Bundle savedInstanceState) {
// ... existing code ...
findViewById(R.id.addButton).setOnClickListener(v -> {
String task = taskInput.getText().toString();
try {
if (!task.isEmpty()) {
tasks.add(task);
adapter.notifyItemInserted(tasks.size() - 1);
taskInput.setText("");
Log.d(TAG, "Task added: " + task);
} else {
throw new IllegalArgumentException("Task cannot be empty");
}
} catch (IllegalArgumentException e) {
Log.e(TAG, "Error: " + e.getMessage());
FirebaseCrashlytics.getInstance().recordException(e);
}
});
}
}7.6 Optimizing the App
Use the Memory Profiler to check for memory leaks in the RecyclerView. Ensure TaskAdapter doesn’t hold references to old views.
8. Conclusion
8.1 Recap of Key Concepts
This chapter covered:
Writing unit tests with JUnit.
Creating UI tests with Espresso.
Debugging with Android Studio tools.
Implementing logging and error tracking.
Optimizing app performance.
8.2 Next Steps in Android Development
Explore advanced topics like:
Integration testing with Robolectric.
Continuous integration with Jenkins or GitHub Actions.
Advanced performance optimization with LeakCanary.
By mastering testing and debugging, you’ll build robust, high-performing Android apps ready for real-world use.
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Md. Mominul Islam