Structure for applying configuration

src/spectator/command_line_arguments_config_source.cr

@@ -0,0 +1,16 @@
+module Spectator
+  # Generates configuration from the command-line arguments.
+  class CommandLineArgumentsConfigSource < ConfigSource
+    # Creates the configuration source.
+    # By default, the command-line arguments (ARGV) are used.
+    # But custom arguments can be passed in.
+    def initialize(@args : Array(String) = ARGV)
+    end
+
+    # Applies the specified configuration to a builder.
+    # Calling this method from multiple sources builds up the final configuration.
+    def apply_to(builder : ConfigBuilder) : Nil
+      # ...
+    end
+  end
+end

src/spectator/config_builder.cr

@@ -0,0 +1,9 @@
+module Spectator
+  class ConfigBuilder
+    property formatter : Formatters::Formatter = Formatters::DefaultFormatter.new
+
+    def build
+      Config.new
+    end
+  end
+end

src/spectator/config_source.cr

@@ -0,0 +1,8 @@
+module Spectator
+  # Interface for all places that configuration can originate.
+  abstract class ConfigSource
+    # Applies the specified configuration to a builder.
+    # Calling this method from multiple sources builds up the final configuration.
+    abstract def apply_to(builder : ConfigBuilder) : Nil
+  end
+end

src/spectator/includes.cr

@@ -23,9 +23,13 @@ require "./example_group"
 require "./nested_example_group"
 require "./root_example_group"
 
+require "./config"
+require "./config_builder"
+require "./config_source"
+require "./command_line_arguments_config_source"
+
 require "./example_failed"
 require "./expectation_failed"
-require "./config"
 require "./test_suite"
 require "./test_suite_results"
 require "./runner"

src/spectator/runner.cr

@@ -1,8 +1,8 @@
 module Spectator
   # Main driver for executing tests and feeding results to formatters.
   class Runner
-    def initialize(@suite : TestSuite,
-                   @formatter : Formatters::Formatter = Formatters::DefaultFormatter.new)
+    def initialize(@suite : TestSuite, config : Config)
+      @formatter = Formatters::DefaultFormatter.new
     end
 
     def run : Nil