function testSet() {
  var tableSchema = schema.table('tableA');
  var indexSchema = tableSchema.getIndices()[0];

  return indexStore.init(schema).then(function() {
    var indexBefore = indexStore.get(indexSchema.getNormalizedName());
    var comparator = lf.index.ComparatorFactory.create(indexSchema);
    var newIndex = new lf.index.BTree(
        indexSchema.getNormalizedName(),
        comparator,
        indexSchema.isUnique);
    indexStore.set(tableSchema.getName(), newIndex);

    var indexAfter = indexStore.get(indexSchema.getNormalizedName());
    assertTrue(indexBefore != indexAfter);
    assertTrue(newIndex == indexAfter);
  });
}
Tests that set() is correctly replacing any existing indices.
@return {!IThenable}