test: add unit tests for CardUtils

AnkiDroid/src/main/java/com/ichi2/anki/CardUtils.kt

@@ -2,28 +2,11 @@
 package com.ichi2.anki
 
 import com.ichi2.anki.libanki.Card
-import com.ichi2.anki.libanki.Collection
-import com.ichi2.anki.libanki.Note
-import com.ichi2.utils.HashUtil.hashSetInit
 
 /**
  * Utilities for working on multiple cards
  */
 object CardUtils {
-    /**
-     * @return List of corresponding notes without duplicates, even if the input list has multiple cards of the same note.
-     */
-    fun getNotes(
-        col: Collection,
-        cards: kotlin.collections.Collection<Card>,
-    ): Set<Note> {
-        val notes: MutableSet<Note> = hashSetInit(cards.size)
-        for (card in cards) {
-            notes.add(card.note(col))
-        }
-        return notes
-    }
-
     /**
      * Returns the deck ID of the given [Card].
      *

AnkiDroid/src/test/java/com/ichi2/anki/CardUtilsTest.kt

@@ -0,0 +1,65 @@
+/*
+ Copyright (c) 2026 Ayush <ayushdevraj9@gmail.com>
+
+ This program is free software; you can redistribute it and/or modify it under
+ the terms of the GNU General Public License as published by the Free Software
+ Foundation; either version 3 of the License, or (at your option) any later
+ version.
+
+ This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package com.ichi2.anki
+
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.hamcrest.MatcherAssert.assertThat
+import org.hamcrest.Matchers.equalTo
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class CardUtilsTest : RobolectricTest() {
+    @Test
+    fun getDeckIdForCard_regularDeck_returnsDid() {
+        val note = addBasicNote("Front", "Back")
+        val card = note.firstCard()
+
+        assertThat("Card should be in a regular deck", card.oDid, equalTo(0L))
+
+        val deckId = CardUtils.getDeckIdForCard(card)
+
+        assertThat("Should return the card's did", deckId, equalTo(card.did))
+    }
+
+    @Test
+    fun getDeckIdForCard_cramDeck_returnsODid() {
+        val note = addBasicNote("Front", "Back")
+        val card = note.firstCard()
+
+        val filteredDid = addDynamicDeck("Filtered")
+        col.sched.rebuildFilteredDeck(filteredDid)
+        card.load()
+
+        assertThat("Card should have oDid set in filtered deck", card.oDid != 0L, equalTo(true))
+
+        val deckId = CardUtils.getDeckIdForCard(card)
+
+        assertThat("Should return the original deck ID (oDid)", deckId, equalTo(card.oDid))
+    }
+
+    @Test
+    fun getDeckIdForCard_zeroODid_returnsDid() {
+        val note = addBasicNote("Front", "Back")
+        val card = note.firstCard()
+
+        assertThat("Card should be in a regular deck", card.oDid, equalTo(0L))
+
+        val deckId = CardUtils.getDeckIdForCard(card)
+
+        assertThat(deckId, equalTo(card.did))
+    }
+}