diff --git a/src/mol-data/int/_spec/ordered-set.spec.ts b/src/mol-data/int/_spec/ordered-set.spec.ts
index 5f717b2dd40dc985026c67eb36ff977dffbb4830..00100fc370d5eff73e3c183e55782f41e12aea96 100644
--- a/src/mol-data/int/_spec/ordered-set.spec.ts
+++ b/src/mol-data/int/_spec/ordered-set.spec.ts
@@ -6,6 +6,7 @@
 
 import OrderedSet from '../ordered-set'
 import Interval from '../interval'
+import SortedArray from '../sorted-array';
 
 describe('ordered set', () => {
     function ordSetToArray(set: OrderedSet) {
@@ -81,6 +82,13 @@ describe('ordered set', () => {
         expect(OrderedSet.isSubset(arr136, OrderedSet.ofSortedArray([12, 13, 16]))).toBe(false);
     });
 
+    it('isSubsetIS', () => {
+        expect(OrderedSet.isSubset(
+            Interval.ofRange(1271, 1295),
+            OrderedSet.ofSortedArray([1271, 1272, 1274, 1275, 1276, 1278, 1280, 1282, 1284, 1286, 1288, 1290, 1292, 1294])
+        )).toBe(true);
+    });
+
     it('access/membership', () => {
         expect(OrderedSet.has(empty, 10)).toBe(false);
         expect(OrderedSet.indexOf(empty, 10)).toBe(-1);
diff --git a/src/mol-data/int/_spec/sorted-array.spec.ts b/src/mol-data/int/_spec/sorted-array.spec.ts
index 8a13d3d5eab384f0abf7cfbd47a092029ab5ea0e..72e6ae28d74fc60cf137dbddea8415ff862cbac6 100644
--- a/src/mol-data/int/_spec/sorted-array.spec.ts
+++ b/src/mol-data/int/_spec/sorted-array.spec.ts
@@ -144,4 +144,11 @@ describe('sortedArray', () => {
             SortedArray.ofSortedArray([3766, 3767, 3768, 3769, 3770, 3773, 3780, 3783, 3787, 3790, 3794, 3797])
         )
     })
+
+    it('isSubset', () => {
+        expect(SortedArray.isSubset(
+            SortedArray.ofSortedArray([1271, 1272, 1273, 1274, 1275, 1276, 1277, 1278, 1279, 1280, 1281, 1282, 1283, 1284, 1285, 1286, 1287, 1288, 1289, 1290, 1291, 1292, 1293, 1294, 1295]),
+            SortedArray.ofSortedArray([1271, 1272, 1274, 1275, 1276, 1278, 1280, 1282, 1284, 1286, 1288, 1290, 1292, 1294])
+        )).toBe(true);
+    })
 });
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