test_avro_schema.rb

require 'avro'

SCHEMA = <<-JSON
{
  "namespace": "com.test.avro.schemas",
  "name": "MyEvent",
  "type": "record",
  "doc": "Some doc.",
  "fields": [
    {
      "name": "tags",
      "type": {
        "type": "array",
        "items": "string"
        },
      "doc": "Something."
    }
  ]
}
JSON

schema = Avro::Schema.parse(SCHEMA)
writer = Avro::IO::DatumWriter.new(SCHEMA)
output = StringIO.new
dw = Avro::DataFile::Writer.new(output, writer, schema)
dw << { 'tags' => ['a', 'b'] }
dw.close

p output.string