// Number of attributes and instances shouldn't change
assertEquals(m_Instances.numAttributes(), result.numAttributes());
assertEquals(m_Instances.numInstances(), result.numInstances());
for (int j = 0; j < m_Instances.numAttributes(); j++) {
Attribute inatt = m_Instances.attribute(j);
Attribute outatt = result.attribute(j);
for (int i = 0; i < m_Instances.numInstances(); i++) {
if (m_Instances.attribute(j).isString()) {
if (m_Instances.instance(i).isMissing(j)) {
assertTrue("Missing values in strings cannot be replaced",
result.instance(i).isMissing(j));