Fix tests to be consistent by deleting env vars first

mix.exs

@@ -4,7 +4,7 @@ defmodule DotenvParser.MixProject do
   def project do
     [
       app: :dotenv_parser,
-      version: "1.1.0",
+      version: "1.1.1",
       elixir: "~> 1.11",
       start_permanent: Mix.env() == :prod,
       deps: deps(),

test/dotenv_parser_test.exs

@@ -2,6 +2,40 @@ defmodule DotenvParserTest do
   use ExUnit.Case
   doctest DotenvParser
 
+  setup do
+    [
+      "BASIC",
+      "AFTER_LINE",
+      "EMPTY",
+      "SINGLE_QUOTES",
+      "SINGLE_QUOTES_SPACED",
+      "DOUBLE_QUOTES",
+      "DOUBLE_QUOTES_SPACED",
+      "EXPAND_NEWLINES",
+      "EXPAND_MANY_SLASHES",
+      "EXPAND_UNICODE",
+      "INVALID_UNICODE",
+      "DONT_EXPAND_UNQUOTED",
+      "DONT_EXPAND_SQUOTED",
+      "EQUAL_SIGNS",
+      "RETAIN_INNER_QUOTES",
+      "RETAIN_LEADING_DQUOTE",
+      "RETAIN_LEADING_SQUOTE",
+      "RETAIN_TRAILING_DQUOTE",
+      "RETAIN_TRAILING_SQUOTE",
+      "RETAIN_INNER_QUOTES_AS_STRING",
+      "TRIM_SPACE_FROM_UNQUOTED",
+      "USERNAME",
+      "SPACED_KEY",
+      "INLINE_COMMENT",
+      "INLINE_COMMENT_PLAIN",
+      "END_BACKSLASH",
+      "lowercased_var",
+      "FOO"
+    ]
+    |> Enum.each(&System.delete_env/1)
+  end
+
   test "parses correctly" do
     assert DotenvParser.parse_file("test/data/.env") == [
              {"BASIC", "basic"},