@Test
public void shouldAddJoinConditionColumnOnLeftSideIfNotAlreadyUsed() {

    // Create a join ...
    PlanNode joinNode = new PlanNode(Type.JOIN);
    joinNode.setProperty(Property.JOIN_TYPE, JoinType.LEFT_OUTER);
    joinNode.setProperty(Property.JOIN_CONDITION, new EquiJoinCondition(selector("left"), "c4", selector("right"), "d2"));
    PlanNode lhs = sourceNode(context, joinNode, "left", "c1", "c2", "c3");
    PlanNode rhs = sourceNode(context, joinNode, "right", "d1", "d2", "d3");
    // Execute the rule ...
    PlanNode result = rule.execute(context, joinNode, new LinkedList<OptimizerRule>());
    assertThat(result, is(sameInstance(joinNode)));
    // Verify nothing has changed ...
    assertThat(joinNode.getProperty(Property.JOIN_TYPE, JoinType.class), is(JoinType.LEFT_OUTER));
    assertThat(joinNode.getFirstChild(), is(sameInstance(lhs)));
    assertThat(joinNode.getLastChild(), is(sameInstance(rhs)));
    assertThat(joinNode.getChildCount(), is(2));
    PlanNode left = joinNode.getFirstChild();
    PlanNode right = joinNode.getLastChild();
    assertProperty(left, Property.PROJECT_COLUMNS, columns(context, selector("left"), "c1", "c2", "c3", "c4"));
    assertProperty(left, Property.PROJECT_COLUMN_TYPES, columnTypes(context, selector("left"), "c1", "c2", "c3", "c4"));
    assertProperty(right, Property.PROJECT_COLUMNS, columns(context, selector("right"), "d1", "d2", "d3"));
    assertProperty(right, Property.PROJECT_COLUMN_TYPES, columnTypes(context, selector("right"), "d1", "d2", "d3"));
}