Added test for querying apps based on category

The previous category tests only checked that certain categories
would indeed find their way into the database if certain app metadata
is saved. It didn't check the other direction, using these categories
in queries.

app/src/test/java/org/fdroid/fdroid/data/AppProviderTest.java

@@ -193,7 +193,7 @@ public class AppProviderTest extends FDroidProviderTest {
         assertContainsOnlyIds(canUpdateApps, expectedCanUpdate);
     }
 
-    private void assertContainsOnlyIds(List<App> actualApps, String[] expectedIds) {
+    public static void assertContainsOnlyIds(List<App> actualApps, String[] expectedIds) {
         List<String> actualIds = new ArrayList<>(actualApps.size());
         for (App app : actualApps) {
             actualIds.add(app.packageName);

app/src/test/java/org/fdroid/fdroid/data/CategoryProviderTest.java

@@ -2,6 +2,8 @@ package org.fdroid.fdroid.data;
 
 import android.app.Application;
 import android.content.ContentValues;
+import android.database.Cursor;
+import android.net.Uri;
 
 import org.fdroid.fdroid.BuildConfig;
 import org.fdroid.fdroid.R;
@@ -16,6 +18,7 @@ import org.robolectric.shadows.ShadowContentResolver;
 import java.util.List;
 
 import static org.fdroid.fdroid.Assert.assertContainsOnly;
+import static org.junit.Assert.assertEquals;
 
 // TODO: Use sdk=24 when Robolectric supports this
 @Config(constants = BuildConfig.class, application = Application.class, sdk = 23)
@@ -34,6 +37,56 @@ public class CategoryProviderTest extends FDroidProviderTest {
     //  use a separate table in the future, these should still pass.
     // ========================================================================
 
+    @Test
+    public void queryAppsInCategories() {
+        insertAppWithCategory("com.dog", "Dog", "Animal");
+        insertAppWithCategory("com.cat", "Cat", "Animal");
+        insertAppWithCategory("com.crow", "Crow", "Animal,Bird");
+        insertAppWithCategory("com.chicken", "Chicken", "Animal,Bird,Food");
+        insertAppWithCategory("com.bird-statue", "Bird Statue", "Bird,Mineral");
+        insertAppWithCategory("com.rock", "Rock", "Mineral");
+        insertAppWithCategory("com.banana", "Banana", "Food");
+
+        assertPackagesInCategory("Animal", new String[] {
+                "com.dog",
+                "com.cat",
+                "com.crow",
+                "com.chicken",
+        });
+
+        assertPackagesInCategory("Bird", new String[]{
+                "com.crow",
+                "com.chicken",
+                "com.bird-statue",
+        });
+
+        assertPackagesInCategory("Food", new String[] {
+                "com.chicken",
+                "com.banana",
+        });
+
+        assertPackagesInCategory("Mineral", new String[] {
+                "com.rock",
+                "com.bird-statue",
+        });
+
+        assertNoPackagesInUri(AppProvider.getCategoryUri("Not a category"));
+    }
+
+    private void assertNoPackagesInUri(Uri uri) {
+        Cursor noApps = contentResolver.query(uri, Cols.ALL, null, null, null);
+        assertEquals(noApps.getCount(), 0);
+    }
+
+    private void assertPackagesInCategory(String category, String[] expectedPackages) {
+        assertPackagesInUri(AppProvider.getCategoryUri(category), expectedPackages);
+    }
+
+    private void assertPackagesInUri(Uri uri, String[] expectedPackages) {
+        List<App> apps = AppProvider.Helper.cursorToList(contentResolver.query(uri, Cols.ALL, null, null, null));
+        AppProviderTest.assertContainsOnlyIds(apps, expectedPackages);
+    }
+
     @Test
     public void testCategoriesSingle() {
         insertAppWithCategory("com.dog", "Dog", "Animal");
@@ -104,5 +157,4 @@ public class CategoryProviderTest extends FDroidProviderTest {
         values.put(Cols.CATEGORIES, categories);
         AppProviderTest.insertApp(contentResolver, context, id, name, values);
     }
-
 }