[Settings] Hide subscriptions not existed within device

For non-active subscriptions, the one inserted in slot
but turned off need to be visible to the user. However,
the one un-plugged need to be invisble.

Since SubscriptionUtil#getSelectableSubscriptionInfoList() didn't cover all the cases required. Create this one to fit into the criteria required here.

Bug: 191228344
Test: local
Change-Id: Ia68c23b007164b7520456cb6c7427ca142558b59

tests/unit/src/com/android/settings/network/helper/SelectableSubscriptionsTest.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.settings.network.helper;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.util.List;
+import java.util.concurrent.atomic.AtomicIntegerArray;
+
+@RunWith(AndroidJUnit4.class)
+public class SelectableSubscriptionsTest {
+
+    @Before
+    public void setUp() {
+    }
+
+
+    @Test
+    public void atomicToList_nullInput_getNoneNullEmptyList() {
+        List<Integer> result = SelectableSubscriptions.atomicToList(null);
+
+        assertThat(result.size()).isEqualTo(0);
+    }
+
+    @Test
+    public void atomicToList_zeroLengthInput_getEmptyList() {
+        List<Integer> result = SelectableSubscriptions.atomicToList(new AtomicIntegerArray(0));
+
+        assertThat(result.size()).isEqualTo(0);
+    }
+
+    @Test
+    public void atomicToList_subIdInArray_getList() {
+        AtomicIntegerArray array = new AtomicIntegerArray(3);
+        array.set(0, 3);
+        array.set(1, 7);
+        array.set(2, 4);
+
+        List<Integer> result = SelectableSubscriptions.atomicToList(array);
+
+        assertThat(result.size()).isEqualTo(3);
+        assertThat(result.get(0)).isEqualTo(3);
+        assertThat(result.get(1)).isEqualTo(7);
+        assertThat(result.get(2)).isEqualTo(4);
+    }
+}