Test Case 2: Renaming headers and ignoring unmapped (returning null) - BROKEN
------------------------------------------------------------------------------
  Transforming "Code Set" to "codeSet"
  Transforming "Code Name" to "codeName"
  Transforming "Code Value" to "codeValue"
  Returning null for header "description"
  Returning null for header "extra_column1"
  Returning null for header "extra_column2"
Duplicate headers found and renamed.
  Returning null for header "codeSet"
  Returning null for header "codeName"
  Returning null for header "codeValue"
  Returning null for header "null"
  Returning null for header "null_1"
  Returning null for header "null_2"

Parsed data (first row):
{
  "null": "Extra Data 2"
}

Total rows parsed: 3

Test Case 3: Using array of headers without renaming - TESTING
---------------------------------------------------------------
  Keeping header "Code Set"
  Keeping header "Code Name"
  Keeping header "Code Value"
  Returning null for header "description"
  Returning null for header "extra_column1"
  Returning null for header "extra_column2"
Duplicate headers found and renamed.
  Keeping header "Code Set"
  Keeping header "Code Name"
  Keeping header "Code Value"
  Returning null for header "null"
  Returning null for header "null_1"
  Returning null for header "null_2"

Parsed data (first row):
{
  "Code Set": "CS001",
  "Code Name": "Test Code",
  "Code Value": "TC123",
  "null": "Extra Data 2"
}

Total rows parsed: 3