Initial mock registry code

src/spectator/mocks/registry.cr

@@ -0,0 +1,45 @@
+module Spectator::Mocks
+  module Registry
+    extend self
+
+    alias Key = Tuple(UInt64, UInt64)
+
+    private struct Entry
+      getter stubs = Deque(MethodStub).new
+      getter calls = Deque(MethodCall).new
+    end
+
+    @entries = {} of Key => Entry
+
+    def reset
+      @entries.clear
+    end
+
+    def register(object)
+      key = unique_key(object)
+      @entries[key] = Entry.new
+    end
+
+    def stub(object, stub : MethodStub)
+      key = unique_key(object)
+      @entries[key].stubs << stub
+    rescue KeyError
+      raise "Cannot stub unregistered mock"
+    end
+
+    def record_call(object, call : MethodCall)
+      key = unique_key(object)
+      @entries[key].calls << call
+    rescue KeyError
+      raise "Cannot record call for unregistered mock"
+    end
+
+    private def unique_key(reference : Reference)
+      {reference.class.hash, reference.object_id}
+    end
+
+    private def unique_key(value : Value)
+      {value.class.hash, value.hash}
+    end
+  end
+end