Detect when to use a verifying double

src/spectator/dsl/mocks.cr

@@ -29,10 +29,15 @@ module Spectator::DSL
   end
 
   macro define_double(type_name, name, **stubs, &block)
-    class {{type_name}} < ::Spectator::Mocks::Double
-      def initialize(null = false)
-        super({{name.id.stringify}}, null)
-      end
+    {% begin %}
+      {% if (name.is_a?(Path) || name.is_a?(Generic)) && (resolved = name.resolve?) %}
+        class {{type_name}} < ::Spectator::Mocks::VerifyingDouble(::{{resolved.id}})
+      {% else %}
+        class {{type_name}} < ::Spectator::Mocks::Double
+          def initialize(null = false)
+            super({{name.id.stringify}}, null)
+          end
+      {% end %}
 
       def as_null_object
         {{type_name}}.new(true)
@@ -42,6 +47,7 @@ module Spectator::DSL
 
       {{block.body}}
     end
+    {% end %}
   end
 
   def anonymous_double(name = "Anonymous", **stubs)

src/spectator/mocks/verifying_double.cr

@@ -0,0 +1,94 @@
+module Spectator::Mocks
+  class VerifyingDouble(T)
+    def initialize(@null = false)
+    end
+
+    private macro stub(definition, &block)
+      {%
+        name = nil
+        params = nil
+        args = nil
+        body = nil
+        if definition.is_a?(Call) # stub foo { :bar }
+          named = false
+          name = definition.name.id
+          params = definition.args
+          args = params.map do |p|
+            n = p.is_a?(TypeDeclaration) ? p.var : p.id
+            r = named ? "#{n}: #{n}".id : n
+            named = true if n.starts_with?('*')
+            r
+          end
+          body = definition.block.is_a?(Nop) ? block : definition.block
+        elsif definition.is_a?(TypeDeclaration) # stub foo : Symbol
+          name = definition.var
+          params = [] of MacroId
+          args = [] of MacroId
+          body = block
+        else
+          raise "Unrecognized stub format"
+        end
+      %}
+
+      def {{name}}({{params.splat}}){% if definition.is_a?(TypeDeclaration) %} : {{definition.type}}{% end %}
+        %args = ::Spectator::Mocks::GenericArguments.create({{args.splat}})
+        %call = ::Spectator::Mocks::GenericMethodCall.new({{name.symbolize}}, %args)
+        ::Spectator::Harness.current.mocks.record_call(self, %call)
+        if (%stub = ::Spectator::Harness.current.mocks.find_stub(self, %call))
+          %stub.call!(%args) { %method({{args.splat}}) }
+        else
+          %method({{args.splat}})
+        end
+      end
+
+      def {{name}}({{params.splat}}){% if definition.is_a?(TypeDeclaration) %} : {{definition.type}}{% end %}
+        %args = ::Spectator::Mocks::GenericArguments.create({{args.splat}})
+        %call = ::Spectator::Mocks::GenericMethodCall.new({{name.symbolize}}, %args)
+        ::Spectator::Harness.current.mocks.record_call(self, %call)
+        if (%stub = ::Spectator::Harness.current.mocks.find_stub(self, %call))
+          %stub.call!(%args) { %method({{args.splat}}) { |*%ya| yield *%ya } }
+        else
+          %method({{args.splat}}) do |*%yield_args|
+            yield *%yield_args
+          end
+        end
+      end
+
+      def %method({{params.splat}}){% if definition.is_a?(TypeDeclaration) %} : {{definition.type}}{% end %}
+        {% if body && !body.is_a?(Nop) %}
+          {{body.body}}
+        {% else %}
+          %args = ::Spectator::Mocks::GenericArguments.create({{params.splat}})
+          %call = ::Spectator::Mocks::GenericMethodCall.new({{name.symbolize}}, %args)
+          unless ::Spectator::Harness.current.mocks.expected?(self, %call)
+            raise ::Spectator::Mocks::UnexpectedMessageError.new("#{self} received unexpected message {{name}}")
+          end
+
+          # This code shouldn't be reached, but makes the compiler happy to have a matching return type.
+          {% if definition.is_a?(TypeDeclaration) %}
+            %x = uninitialized {{definition.type}}
+          {% else %}
+            nil
+          {% end %}
+        {% end %}
+      end
+    end
+
+    macro method_missing(call)
+      args = ::Spectator::Mocks::GenericArguments.create({{call.args.splat}})
+      call = ::Spectator::Mocks::GenericMethodCall.new({{call.name.symbolize}}, args)
+      ::Spectator::Harness.current.mocks.record_call(self, call)
+
+      return self if @null
+      return self if ::Spectator::Harness.current.mocks.expected?(self, call)
+
+      raise ::Spectator::Mocks::UnexpectedMessageError.new("#{self} received unexpected message {{call.name}}")
+    end
+
+    def to_s(io)
+      io << "Double("
+      io << T
+      io << ')'
+    end
+  end
+end