Migration V1 halt case

squarenotsquare/__tests__/Migration-test.js

@@ -22,3 +22,12 @@ test('Realm migrates to V1', () => {
     expect(newRealm[System.name][0].key).toBe('username');
     expect(newRealm[System.name][0].value).toBe('changeme');
 })
+
+test('Realm halts V1 migration when schema is V2+', () => {
+    let oldRealm = new MockRealm(2);
+    newRealm = new MockRealm(1);
+    migratev1(oldRealm, newRealm);
+    oldRealm.create(System.name, {key: 'key1', value: 'value'})
+
+    expect(oldRealm[System.name].length).toBe(1);
+})