Added tests to support Unit tests Write tests for SearchCountryUseCase class. Make sure that all cases are covered. Recommended to use Parametrized test. Write tests for CountriesViewModel. Highly recommend to cover search functionality. Ui tests Write tests for CountryDetailsFragment. Write tests for CountryFragment.

app/src/main/androidTest/java/CountryFragmentTest.kt

@@ -0,0 +1,40 @@
+import androidx.fragment.app.testing.FragmentScenario;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import androidx.test.espresso.Espresso;
+import androidx.test.espresso.assertion.ViewAssertions;
+import androidx.test.espresso.matcher.ViewMatchers;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import static androidx.test.espresso.matcher.ViewMatchers.withText;
+import androidx.fragment.app.testing.FragmentScenario;
+import androidx.test.espresso.Espresso;
+import androidx.test.espresso.assertion.ViewAssertions;
+import androidx.test.espresso.matcher.ViewMatchers;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@RunWith(AndroidJUnit4.class)
+public class CountryDetailsFragmentTest {
+
+    @Test
+    public void testCountryDetailsDisplayed() {
+        FragmentScenario.launchInContainer(CountryDetailsFragment.class);
+
+        // Assuming the text view with country name has the ID country_name_textview
+        Espresso.onView(ViewMatchers.withId(R.id.country_name_textview))
+                .check(ViewAssertions.matches(withText("USA")));
+    }
+}
+@RunWith(AndroidJUnit4.class)
+public class CountryFragmentTest {
+
+    @Test
+    public void testCountryListDisplayed() {
+        FragmentScenario.launchInContainer(CountryFragment.class);
+
+        // Assuming the RecyclerView for countries has the ID countries_recycler_view
+        Espresso.onView(ViewMatchers.withId(R.id.countries_recycler_view))
+                .check(ViewAssertions.matches(ViewMatchers.isDisplayed()));
+    }
+}

app/src/main/java/com/example/walmart/WalmartApplication.kt

@@ -7,6 +7,21 @@ import com.example.walmart.domain.di.ServiceProvider
 import com.example.walmart.domain.di.add
 import com.example.walmart.domain.di.module
 import com.example.walmart.presentation.di.presentationModule
+import static org.junit.Assert.*;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import java.util.Arrays;
+import java.util.List;
+import androidx.arch.core.executor.testing.InstantTaskExecutorRule;
+import androidx.lifecycle.Observer;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import static org.mockito.Mockito.verify;
 
 class WalmartApplication : Application() {
 
@@ -20,4 +35,62 @@ class WalmartApplication : Application() {
             module { add { applicationContext } }
         )
     }
+
+//This test will check the SearchCountryUseCase for different cases:
+//Empty search returns all countries.
+//Exact match returns the correct country.
+//No match returns an empty list.
+
+@RunWith(Parameterized.class)
+public class SearchCountryUseCaseTest {
+
+    private final String searchQuery;
+    private final List<String> expectedCountries;
+
+    public SearchCountryUseCaseTest(String searchQuery, List<String> expectedCountries) {
+        this.searchQuery = searchQuery;
+        this.expectedCountries = expectedCountries;
+    }
+
+    @Parameterized.Parameters
+    public static Iterable<Object[]> data() {
+        return Arrays.asList(new Object[][]{
+            {"", Arrays.asList("USA", "Canada", "Mexico")},  // All countries
+            {"USA", Arrays.asList("USA")},                  // One country match
+            {"xyz", Arrays.asList()},                        // No match
+        });
+    }
+
+    @Test
+    public void testSearchCountry() {
+        SearchCountryUseCase useCase = new SearchCountryUseCase();
+        List<String> result = useCase.searchCountries(searchQuery);
+        assertEquals(expectedCountries, result);
+    }
+}
+
+public class CountriesViewModelTest {
+
+    @Rule
+    public InstantTaskExecutorRule instantTaskExecutorRule = new InstantTaskExecutorRule();
+
+    private CountriesViewModel viewModel;
+
+    @Mock
+    private Observer<List<String>> observer;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        viewModel = new CountriesViewModel();
+        viewModel.getCountries().observeForever(observer);
+    }
+
+    @Test
+    public void testSearch() {
+        String query = "USA";
+        viewModel.searchCountries(query);
+        verify(observer).onChanged(Arrays.asList("USA"));  // Expect that search returns USA
+    }
+}
 }