function checkEvalRelations_MultiJoin(evalFn) {
  var sampleRows = getSampleRows();

  var employeeRelation = lf.proc.Relation.fromRows(
      sampleRows.employees, [e.getName()]);
  var jobRelation = lf.proc.Relation.fromRows(
      sampleRows.jobs, [j.getName()]);
  var departmentRelation = lf.proc.Relation.fromRows(
      sampleRows.departments, [d.getName()]);

  var joinPredicate1 = e.jobId.eq(j.id);
  var joinPredicate2 = e.departmentId.eq(d.id);

  var resultEmployeeJob = evalFn.call(
      joinPredicate1, employeeRelation, jobRelation, false);
  var resultEmployeeJobDepartment = evalFn.call(
      joinPredicate2, resultEmployeeJob, departmentRelation, false);
  assertEquals(
      sampleRows.employees.length,
      resultEmployeeJobDepartment.entries.length);
}
Checks that the given join implementation is correct, for the case where a 3
table natural join is performed.
@param {!function(!lf.proc.Relation, !lf.proc.Relation, boolean)
    :!lf.proc.Relation} evalFn The join implementation method should be
    either evalRelationsNestedLoopJoin_ or evalRelationsHashJoin_.