Allow passing predefined stubs in as keyword args

spec/spectator/dsl/mocks/double_spec.cr

@@ -208,6 +208,16 @@ Spectator.describe "Double DSL" do
     end
   end
 
+  describe "predefined method stubs" do
+    double(:test8, foo: 42)
+
+    let(dbl) { double(:test8, foo: 7) }
+
+    it "overrides the original value" do
+      expect(dbl.foo).to eq(7)
+    end
+  end
+
   describe "scope" do
     double(:outer, scope: :outer)
     double(:scope, scope: :outer)

spec/spectator/dsl/mocks/null_double_spec.cr

@@ -176,4 +176,14 @@ Spectator.describe "Null double DSL" do
       end
     end
   end
+
+  describe "predefined method stubs" do
+    double(:test8, foo: 42)
+
+    let(dbl) { double(:test8, foo: 7).as_null_object }
+
+    it "overrides the original value" do
+      expect(dbl.foo).to eq(7)
+    end
+  end
 end

src/spectator/dsl/mocks.cr

@@ -95,7 +95,7 @@ module Spectator::DSL
  found_tuple = found_tuples.last %}
 
       {% if found_tuple %}
-        {{found_tuple[2].id}}.new
+        {{found_tuple[2].id}}.new({{**value_methods}})
       {% else %}
         ::Spectator::LazyDouble.new({{name}}, {{**value_methods}})
       {% end %}

src/spectator/mocks/double.cr

@@ -4,6 +4,7 @@ require "./stub"
 require "./stubbable"
 require "./stubbed_name"
 require "./unexpected_message"
+require "./value_stub"
 
 module Spectator
   # Stands in for an object for testing that a SUT calls expected methods.
@@ -76,6 +77,15 @@ module Spectator
     def initialize(@stubs : Array(Stub) = [] of Stub)
     end
 
+    # Creates the double.
+    #
+    # An initial set of stubs can be provided with *value_methods*.
+    def initialize(**value_methods)
+      @stubs = value_methods.map do |key, value|
+        ValueStub.new(key, value).as(Stub)
+      end
+    end
+
     # Compares against another object.
     #
     # Always returns false.