Introduce a dynamic test mechanism

lib/ex_format.ex

@@ -47,6 +47,11 @@ defmodule ExFormat do
   def process(file_name) do
     file_name
     |> File.read!
+    |> process_string
+  end
+
+  def process_string(string) do
+    string
     |> prepare_data
     |> preprocess
     |> format

test/cases/kw_list.exs

@@ -0,0 +1,38 @@
+#=- CASE: Multiple function heads
+#=- BEFORE:
+def func1(a1,b1) do
+  func3(a,b)
+  1+2
+end
+def func1(a1,b1) do
+  func3(a,b)
+end
+def func1(a1,b1) do
+    func3(a,b)
+end
+
+
+#=- AFTER:
+def func1(a1, b1) do
+  func3(a, b)
+  1 + 2
+end
+def func1(a1, b1) do
+  func3(a, b)
+end
+def func1(a1, b1) do
+  func3(a, b)
+end
+#=-
+#=- CASE: Preserve keyword list syntax
+#=- BEFORE:
+#=-
+def   func2(a2,b2),   do: func3(a,b)
+def func2(a2,b2), do:       func3(a,b)
+def func2(a2,   b2), do: func3(a,b)
+
+
+#=- AFTER:
+def func2(a2, b2), do: func3(a, b)
+def func2(a2, b2), do: func3(a, b)
+def func2(a2, b2), do: func3(a, b)

test/cases/prefix_comments.exs

@@ -0,0 +1,18 @@
+#=-
+#=- CASE: Preserve comments
+#=- BEFORE:
+#=-
+# prefix comment preserved
+def hello(name) do
+    # prefix comment preserved
+    "hello " <> name
+end
+#=-
+#=- AFTER:
+#=-
+# prefix comment preserved
+def hello(name) do
+  # prefix comment preserved
+  "hello " <> name
+end
+#=-

test/comparison_test.exs

@@ -0,0 +1,24 @@
+defmodule ComparisonTest do
+  use ExUnit.Case, async: true
+
+  @case_dir "test/cases"
+  @case_split "#=- CASE:"
+  @case_spacer "#=-\n"
+  @case_extractor ~r/(?<name>.*)#=- BEFORE:\n(?<before_string>.*)\n#=- AFTER:\n(?<after_string>.*)/s
+
+  Enum.map(File.ls!(@case_dir), fn file ->
+    File.read!("#{@case_dir}/#{file}")
+    |> String.replace(@case_spacer, "")
+    |> String.split(@case_split, trim: true)
+    |> Enum.map(fn test_case ->
+         %{"name" => name, "before_string" => before_string, "after_string" => after_string} =
+           Regex.named_captures(@case_extractor, test_case)
+         function_name = ExUnit.Case.register_test(__ENV__, :test, "#{String.trim(name)} (#{file})", [])
+         def unquote(function_name)(_) do
+           formatted = ExFormat.process_string(unquote(before_string))
+           expected = unquote(after_string)
+           assert formatted == expected
+         end
+       end)
+  end)
+end