Extract values from maps

lib/koans/03_maps.ex

@@ -4,62 +4,62 @@ defmodule Maps do
   koan "Maps represent structured data, like a person" do
     assert %{ :name => "Jon",
               :last_name => "Snow",
-              :age => 27 } == %{ :name => "Jon",
+              :age => 27 } == %{ :name => :__,
                                  :last_name => "Snow",
                                  :age => 27 }
   end
 
   koan "You can get all the keys from the map" do
-    assert Map.keys(%{ :name => "Jon", :last_name => "Snow", :age => 27 }) == [:age, :last_name, :name]
+    assert Map.keys(%{ :name => "Jon", :last_name => "Snow", :age => 27 }) == :__
   end
 
   koan "Or you can also get all the values from it" do
-    assert Map.values(%{ :name => "Jon", :last_name => "Snow", :age => 27 }) == [27, "Snow", "Jon"]
+    assert Map.values(%{ :name => "Jon", :last_name => "Snow", :age => 27 }) == :__
   end
 
   koan "Fetching a value returns a touple with ok when it exists..." do
-    assert Map.fetch(%{ :name => "Jon", :last_name => "Snow", :age => 27 }, :age) == {:ok, 27}
+    assert Map.fetch(%{ :name => "Jon", :last_name => "Snow", :age => 27 }, :age) == :__
   end
 
   koan "...or the atom :error when it doesnt." do
-    assert Map.fetch(%{ :name => "Jon", :last_name => "Snow", :age => 27 }, :family) == :error
+    assert Map.fetch(%{ :name => "Jon", :last_name => "Snow", :age => 27 }, :family) == :__
   end
 
   koan "Extending a map is a simple as put'ing in a new pair" do
-    assert Map.put(%{ :name => "Jon", :last_name => "Snow"}, :age, 27) == %{ :name => "Jon", :last_name => "Snow", :age => 27 }
+    assert Map.put(%{ :name => "Jon", :last_name => "Snow"}, :age, 27) == :__
   end
 
   koan "Put can also overwrite existing values" do
-    assert Map.put(%{ :name => "Jon", :last_name => "Snow", :age => 15}, :age, 27) == %{ :name => "Jon", :last_name => "Snow", :age => 27 }
+    assert Map.put(%{ :name => "Jon", :last_name => "Snow", :age => 15}, :age, 27) == :__
   end
 
   koan "Or you can use some syntactic sugar for exiting elements." do
-    initial = %{ :name => "Jon", :last_name => "Snow", :age => 15}
-    assert %{ initial | :age => 27 } == %{ :name => "Jon", :last_name => "Snow", :age => 27 }
+    initial = %{ :name => "Jon", :last_name => "Snow", :age => 16}
+    assert %{ initial | :age => 27 } == :__
   end
 
   koan "Can remove pairs by key" do
-    assert Map.delete(%{ :name => "Jon", :last_name => "Snow", :age => 15}, :age) == %{ :name => "Jon", :last_name => "Snow"}
+    assert Map.delete(%{ :name => "Jon", :last_name => "Snow", :age => 15}, :age) == :__
   end
 
   koan "If you have a list of pairs, you can turn them into a map" do
-    assert Map.new( [{:name, "Jon"}, {:last_name, "Snow"}, {:age, 27}] ) == %{ :name => "Jon", :last_name => "Snow", :age => 27 }
+    assert Map.new( [{:name, "Jon"}, {:last_name, "Snow"}, {:age, 27}] ) == :__
   end
 
   koan "Going back to a list of pairs is just as easy." do
-    assert Map.to_list(%{ :name => "Jon", :last_name => "Snow", :age => 27 }) == [age: 27, last_name: "Snow", name: "Jon" ]
+    assert Map.to_list(%{ :name => "Jon", :last_name => "Snow", :age => 27 }) == :__
   end
 
   koan "Can merge maps" do
-    assert Map.merge(%{:name => "Jon"}, %{ :last_name => "Snow"}) == %{:name => "Jon", :last_name => "Snow"}
+    assert Map.merge(%{:name => "Jon"}, %{ :last_name => "Snow"}) == :__
   end
 
   koan "When merging, the last map wins" do
-    assert Map.merge(%{:name => "Robert", :last_name => "Snow"}, %{ :last_name => "Baratheon"}) == %{:name => "Robert", :last_name => "Baratheon"}
+    assert Map.merge(%{:name => "Robert", :last_name => "Snow"}, %{ :last_name => "Baratheon"}) == :__
   end
 
   koan "You can also select sub-maps out of a larger map" do
     initial = %{ :name => "Jon", :last_name => "Snow", :age => 15}
-    assert Map.take(initial, [:name, :last_name]) == %{ :name => "Jon", :last_name => "Snow"}
+    assert Map.take(initial, [:name, :last_name]) == :__
   end
 end

test/koans_harness_test.exs

@@ -34,6 +34,27 @@ defmodule KoansHarnessTest do
     test_all(Lists, answers)
   end
 
+  test "Maps" do
+    answers = [
+      "Jon",
+      [:age, :last_name, :name],
+      [27, "Snow", "Jon"],
+      {:ok, 27},
+      :error,
+      %{ :name => "Jon", :last_name => "Snow", :age => 27 },
+      %{ :name => "Jon", :last_name => "Snow", :age => 27 },
+      %{ :name => "Jon", :last_name => "Snow", :age => 27 },
+      %{ :name => "Jon", :last_name => "Snow"},
+      %{ :name => "Jon", :last_name => "Snow", :age => 27 },
+      [age: 27, last_name: "Snow", name: "Jon" ],
+      %{:name => "Jon", :last_name => "Snow"},
+      %{:name => "Robert", :last_name => "Baratheon"},
+      %{ :name => "Jon", :last_name => "Snow"}
+    ]
+
+    test_all(Maps, answers)
+  end
+
   def test_all(module, answers) do
     module.all_koans
     |> Enum.zip(answers)