Sketch out the structure for backends

lib/minitrace.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "minitrace/version"
+require "minitrace/backends"
 require "minitrace/event"
 
 # A minimalist tracing framework.

lib/minitrace/backend.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class Minitrace::Backend
+  def process(event)
+    raise NotImplementedError
+  end
+end

lib/minitrace/backends.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+require "minitrace/backend"
+
+module Minitrace::Backends
+  autoload :Spy, "minitrace/backends/spy"
+end

lib/minitrace/backends/spy.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class Minitrace::Backends::Spy < Minitrace::Backend
+  def processed
+    @processed ||= []
+  end
+
+  def process(event)
+    processed << event
+  end
+end

test/lib/minitrace/backends/spy_test.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class Minitrace::Backends::SpyTest < Minitest::Test
+  def test_process
+    spy = Minitrace::Backends::Spy.new
+
+    a = Minitrace::Event.new
+    spy.process(a)
+
+    b = Minitrace::Event.new
+    spy.process(b)
+
+    c = Minitrace::Event.new
+    spy.process(c)
+
+    assert { spy.processed == [a, b, c] }
+  end
+end