test: verify Arabic highlighting on Android runtime

arabickit/build.gradle.kts

@@ -11,6 +11,7 @@ android {
 
     defaultConfig {
         minSdk = 24
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
         consumerProguardFiles("consumer-rules.pro")
     }
 
@@ -37,4 +38,7 @@ android {
 
 dependencies {
     testImplementation("junit:junit:4.13.2")
+
+    androidTestImplementation("androidx.test:runner:1.7.0")
+    androidTestImplementation("androidx.test.ext:junit:1.3.0")
 }

arabickit/src/androidTest/kotlin/io/github/khalid567cpu/arabickit/ArabicHighlighterInstrumentedTest.kt

@@ -0,0 +1,45 @@
+package io.github.khalid567cpu.arabickit
+
+import android.graphics.Color
+import android.text.style.BackgroundColorSpan
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+public class ArabicHighlighterInstrumentedTest {
+    @Test
+    public fun highlightBackground_mapsNormalizedMatchesToOriginalArabicText() {
+        val source = "إِنَّ الــلَّهَ غَفُورٌ، إن الله رحيم ٢٠٢٦"
+
+        val highlighted = ArabicHighlighter.highlightBackground(
+            text = source,
+            query = "ان الله",
+            color = Color.YELLOW,
+        )
+
+        val spans = highlighted
+            .getSpans(0, highlighted.length, BackgroundColorSpan::class.java)
+            .sortedBy(highlighted::getSpanStart)
+
+        assertEquals(2, spans.size)
+        assertTrue(spans.all { it.backgroundColor == Color.YELLOW })
+
+        val highlightedSubstrings = spans.map { span ->
+            source.substring(
+                highlighted.getSpanStart(span),
+                highlighted.getSpanEnd(span),
+            )
+        }
+
+        assertEquals(
+            listOf(
+                "إِنَّ الــلَّهَ",
+                "إن الله",
+            ),
+            highlightedSubstrings,
+        )
+    }
+}