diff --git a/.github/workflows/actions.yml b/.github/workflows/actions.yml
index 4104e22..616781a 100644
--- a/.github/workflows/actions.yml
+++ b/.github/workflows/actions.yml
@@ -1,4 +1,5 @@
-name: Build
+name: Build and Test
+
 on:
   push:
     branches: [ master ]
@@ -19,3 +20,33 @@ jobs:
         uses: gradle/actions/setup-gradle@v4
       - name: Build with Gradle
         run: ./gradlew build
+
+  instrumented-tests:
+    needs: build
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        locale: ['en-US', 'de-DE', 'es-ES', 'ar-EG']
+    steps:
+      - name: checkout
+        uses: actions/checkout@v4
+
+      - name: Set locale properties
+        id: locale_props
+        run: |
+          echo "language=$(echo ${{ matrix.locale }} | cut -d'-' -f1)" >> $GITHUB_OUTPUT
+          echo "country=$(echo ${{ matrix.locale }} | cut -d'-' -f2)" >> $GITHUB_OUTPUT
+
+      - name: Enable KVM
+        run: |
+          echo 'KERNEL=="kvm", GROUP="kvm", MODE="0666", OPTIONS+="static_node=kvm"' | sudo tee /etc/udev/rules.d/99-kvm4all.rules
+          sudo udevadm control --reload-rules
+          sudo udevadm trigger --name-match=kvm
+
+      - name: Run Instrumented Tests for ${{ matrix.locale }}
+        uses: reactivecircus/android-emulator-runner@v2
+        with:
+          api-level: 33
+          arch: x86_64
+          emulator-options: "-no-window -no-snapshot -prop persist.sys.language=${{ steps.locale_props.outputs.language }} -prop persist.sys.country=${{ steps.locale_props.outputs.country }}"
+          script: ./gradlew connectedAndroidTest
diff --git a/app/src/androidTest/java/atorch/statspuzzles/PuzzleSelectionTest.java b/app/src/androidTest/java/atorch/statspuzzles/PuzzleSelectionTest.java
new file mode 100644
index 0000000..785f739
--- /dev/null
+++ b/app/src/androidTest/java/atorch/statspuzzles/PuzzleSelectionTest.java
@@ -0,0 +1,37 @@
+package atorch.statspuzzles;
+
+import android.content.Context;
+import androidx.test.platform.app.InstrumentationRegistry;
+import androidx.test.ext.junit.rules.ActivityScenarioRule;
+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 static androidx.test.espresso.action.ViewActions.click;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@RunWith(AndroidJUnit4.class)
+public class PuzzleSelectionTest {
+
+    @Rule
+    public ActivityScenarioRule<PuzzleSelection> activityRule =
+            new ActivityScenarioRule<>(PuzzleSelection.class);
+
+    @Test
+    public void mainActivityLoads() {
+        Context context = InstrumentationRegistry.getInstrumentation().getTargetContext();
+        Espresso.onView(ViewMatchers.withText(context.getString(R.string.app_name)))
+                .check(ViewAssertions.matches(ViewMatchers.isDisplayed()));
+    }
+
+    @Test
+    public void easyPuzzlesButton_loadsEasyPuzzles() {
+        Context context = InstrumentationRegistry.getInstrumentation().getTargetContext();
+        Espresso.onView(ViewMatchers.withText(context.getString(R.string.button_level_0))).perform(click());
+        Espresso.onView(ViewMatchers.withText(context.getString(R.string.puzzle, 1)))
+                .check(ViewAssertions.matches(ViewMatchers.isDisplayed()));
+    }
+}
diff --git a/app/src/main/res/values-de/strings.xml b/app/src/main/res/values-de/strings.xml
index e905209..e4838b4 100644
--- a/app/src/main/res/values-de/strings.xml
+++ b/app/src/main/res/values-de/strings.xml
@@ -67,7 +67,7 @@
     <string name="okay_button">Okay</string>
     <string name="ok_button">OK</string>
 
-    <string name="solved">%d/%d gelöst</string>
+    <string name="solved">%1$d/%2$d gelöst</string>
 
     <string name="action_share">Teilen</string>
     <string name="action_settings">Einstellungen</string>
diff --git a/app/src/main/res/values-es/strings.xml b/app/src/main/res/values-es/strings.xml
index 2b09b7b..d64a69f 100644
--- a/app/src/main/res/values-es/strings.xml
+++ b/app/src/main/res/values-es/strings.xml
@@ -70,7 +70,7 @@
     <string name="okay_button">De acuerdo</string>
     <string name="ok_button">OK</string>
 
-    <string name="solved">Resueltos %d / %d</string>
+    <string name="solved">Resueltos %1$d / %2$d</string>
 
     <string name="action_share">Compartir</string>
     <string name="action_settings">Configuración</string>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 3e10612..fb74053 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -70,7 +70,7 @@
     <string name="okay_button">Okay</string>
     <string name="ok_button">OK</string>
 
-    <string name="solved">solved %d / %d</string>
+    <string name="solved">solved %1$d / %2$d</string>
 
     <string name="action_share">Share</string>
     <string name="action_settings">Settings</string>
diff --git a/app/src/test/java/atorch/statspuzzles/AnswerCheckerTest.java b/app/src/test/java/atorch/statspuzzles/AnswerCheckerTest.java
index e2e7d1e..8febe86 100644
--- a/app/src/test/java/atorch/statspuzzles/AnswerCheckerTest.java
+++ b/app/src/test/java/atorch/statspuzzles/AnswerCheckerTest.java
@@ -9,6 +9,10 @@ public class AnswerCheckerTest {
     public void testCorrectAnswer() {
         assertEquals(AnswerChecker.Result.CORRECT, AnswerChecker.checkAnswer("2+2", "4"));
         assertEquals(AnswerChecker.Result.CORRECT, AnswerChecker.checkAnswer("1/2", "0.5"));
+        assertEquals(AnswerChecker.Result.CORRECT, AnswerChecker.checkAnswer("3!", "6.0"));
+        // Note that we have a Result.INACCURATE version of this test as well
+        assertEquals(AnswerChecker.Result.CORRECT, AnswerChecker.checkAnswer("1/3", "0.33333333333333"));
+        assertEquals(AnswerChecker.Result.CORRECT, AnswerChecker.checkAnswer("C(5, 3)", "10"));
     }
 
     @Test
@@ -19,11 +23,15 @@ public void testInaccurateAnswer() {
     @Test
     public void testIncorrectAnswer() {
         assertEquals(AnswerChecker.Result.INCORRECT, AnswerChecker.checkAnswer("1", "2"));
+        // The user's answer is not close enough to be considered merely inaccurate.
+        assertEquals(AnswerChecker.Result.INCORRECT, AnswerChecker.checkAnswer("1/3", "0.33"));
     }
 
     @Test
     public void testInvalidAnswer() {
         assertEquals(AnswerChecker.Result.INVALID, AnswerChecker.checkAnswer("1", "abc"));
         assertEquals(AnswerChecker.Result.INVALID, AnswerChecker.checkAnswer("1", ""));
+        // Imbalanced parentheses
+        assertEquals(AnswerChecker.Result.INVALID, AnswerChecker.checkAnswer("( 1 + 5", ""));
     }
 }