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Property-Based Testing with PropEr in Elixir

CSV Parsing: The CSV Parser

Explore how to implement a CSV parser in Elixir using property-based testing with PropEr. Understand encoding and decoding strategies, manage edge cases in CSV data, and combine property-based tests with example-based unit tests to ensure robustness and reliability.

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The CSV parser

We can now move on to implementing a CSV parser. Here is a possible implementation:

Shell
defmodule Bday.Csv do
  def encode([]), do: ""
  def encode(maps) do
    keys = Enum.map_join(Map.keys(hd(maps)), ",", &escape(&1))
    vals =
      for map <- maps, do: Enum.map_join(Map.values(map), ",", &escape(&1))
    to_string([keys, "\r\n", Enum.join(vals, "\r\n")])
  end
  def decode(""), do: []
  def decode(csv) do
    {headers, rest} = decode_header(csv, [])
    rows = decode_rows(rest)
    for row <- rows, do: Map.new(Enum.zip(headers, row))
  end
end

Note: Decoding is done by fetching the headers, then fetching all of the rows. A header line is parsed by reading each column name one at a time, and a row is parsed by reading each field one at a time.

First, there’s the public interface with two functions:

  1. encode/1
  2. decode/1.

The functions are fairly straightforward, delegating the more complex operations to ...