Add tests for performanceLevel mapping

Co-authored-by: alvin000009238 <107313913+alvin000009238@users.noreply.github.com>

Author: google-labs-jules[bot]

android/app/src/main/java/com/clhs/score/data/GradeAnalysis.kt

@@ -485,7 +485,7 @@ private fun summaryText(
         .plus("。")
 }
 
-private fun performanceLevel(topPercent: Int): String = when {
+internal fun performanceLevel(topPercent: Int): String = when {
     topPercent <= 25 -> "班級前段"
     topPercent <= 50 -> "中上"
     topPercent <= 75 -> "中段"

android/app/src/test/java/com/clhs/score/data/GradeAnalysisTest.kt

@@ -357,6 +357,18 @@ class GradeAnalysisTest {
         )
     }
 
+    @Test
+    fun performanceLevelMapsTopPercentCorrectly() {
+        assertEquals("班級前段", performanceLevel(1))
+        assertEquals("班級前段", performanceLevel(25))
+        assertEquals("中上", performanceLevel(26))
+        assertEquals("中上", performanceLevel(50))
+        assertEquals("中段", performanceLevel(51))
+        assertEquals("中段", performanceLevel(75))
+        assertEquals("需要加強", performanceLevel(76))
+        assertEquals("需要加強", performanceLevel(100))
+    }
+
     @Test
     fun localInsightsDoNotEstimateRankWhenRankDataMissing() {
         val current = MockGradeSystem.generateReport(customClassRank = null)