Make sure blank is on the right and improve koans

lib/koans/02_strings.ex

@@ -10,11 +10,11 @@ defmodule Strings do
   end
 
   koan "Or pulled apart when needed" do
-    assert ___ == String.split("hello world")
+    assert ["hello", "world"] == String.split(___, " ")
   end
 
   koan "Be careful, a message may be altered" do
-    assert ___ == String.replace("An awful day", "awful", "incredible")
+    assert String.replace("An awful day", "awful", "incredible") == ___
   end
 
   koan "But strings never lie about themselves" do
@@ -26,7 +26,7 @@ defmodule Strings do
   end
 
   koan "Other times a little cleaning is in order" do
-    assert ___ == String.strip("  \n banana\n  ")
+    assert String.strip("  \n banana\n  ") == ___
   end
 
   koan "Repetition is the mother of learning" do

lib/koans/03_tuples.ex

@@ -1,14 +1,14 @@
 defmodule Tuples do
   use Koans
 
-  koan "Tuples have a size" do
-    assert tuple_size({:a, :b, :c}) == ___
-  end
-
   koan "Tuples can contain different things" do
     assert {:a, 1, "hi"} == ___
   end
 
+  koan "Tuples have a size" do
+    assert tuple_size({:a, :b, :c}) == ___
+  end
+
   koan "You can pull out individual elements" do
     assert elem({:a, "hi"}, 1) == ___
   end

lib/koans/04_lists.ex

@@ -33,10 +33,6 @@ defmodule Lists do
     assert List.flatten([1, [2, 3], 4, [5]]) == ___
   end
 
-  koan "Same rules apply to new members that arrive late" do
-    assert List.flatten([1, [2, 3]], [4]) == ___
-  end
-
   koan "Order can also be specified for new members" do
     assert List.insert_at([1, 2, 3], 1, 4) == ___
   end
@@ -45,7 +41,7 @@ defmodule Lists do
     assert List.replace_at([1, 2, 3], 0, 10) == ___
   end
 
-  koan "Replacing something which is not" do
+  koan "When a replacement cannot be found, the list remains the same" do
     assert List.replace_at([1, 2, 3], 10, 0) == ___
   end
 
@@ -62,10 +58,6 @@ defmodule Lists do
   end
 
   koan "Wrapping other values is a handy option" do
-    assert List.wrap("value") == :___
-  end
-
-  koan "Zipping can be a useful operation" do
-    assert List.zip([[1, 2], [3, 4], [5, 6]]) == :___
+    assert List.wrap("value") == ___
   end
 end

lib/koans/06_structs.ex

@@ -10,7 +10,7 @@ defmodule Structs do
     assert person == ___
   end
 
-  koan "You can access the fields of a struct" do
+  koan "Unless previously defined, fields begin as nil" do
     nobody = %Person{}
     assert nobody.age == ___
   end
@@ -26,17 +26,6 @@ defmodule Structs do
     assert older.age == ___
   end
 
-  koan "The original struct is not affected by updates" do
-    joe = %Person{name: "Joe", age: 23}
-    assert %{ joe | age: joe.age + 10}.age == ___
-    assert joe.age == ___
-  end
-
-  koan "You can pattern match into the fields of a struct" do
-    %Person{age: age} = %Person{age: 22, name: "Silvia"}
-    assert age == ___
-  end
-
   defmodule Plane do
     defstruct passengers: 0, maker: :boeing
   end
@@ -49,7 +38,7 @@ defmodule Structs do
     assert plane?(%Person{}) == ___
   end
 
-  koan "Are basically maps" do
+  koan "Struct can be treated like maps" do
     silvia = %Person{age: 22, name: "Silvia"}
 
     assert Map.fetch!(silvia, :age) == ___

lib/koans/07_pattern_matching.ex

@@ -56,21 +56,32 @@ defmodule PatternMatching do
   def make_noise(_anything), do: "Eh?"
 
   koan "Functions can declare what kind of arguments they accept" do
-    dog = %{type: "dog", legs: 4, age: 9, color: "brown"}
-    cat = %{type: "cat", legs: 4, age: 3, color: "grey"}
-    snake = %{type: "snake", legs: 0, age: 20, color: "black"}
+    dog = %{type: "dog"}
+    cat = %{type: "cat"}
+    snake = %{type: "snake"}
 
-    assert make_noise(dog) == ___
     assert make_noise(cat) == ___
+    assert make_noise(dog) == ___
     assert make_noise(snake) == ___
   end
 
   koan "Errors are shaped differently than sucessful results" do
-    result = case Map.fetch(%{}, :obviously_not_a_key) do
+    dog = %{type: "dog"}
+
+    result = case Map.fetch(dog, :type) do
+      {:ok, value} -> value
       :error -> "not present"
-      _ -> flunk("I should not happen")
     end
 
     assert result == ___
   end
+
+  defmodule Animal do
+    defstruct [:kind, :name]
+  end
+
+  koan "You can pattern match into the fields of a struct" do
+    %Animal{name: name} = %Animal{kind: "dog", name: "Max"}
+    assert name == ___
+  end
 end

lib/koans/08_functions.ex

@@ -11,7 +11,7 @@ defmodule Functions do
 
   def multiply(a, b), do: a * b
   koan "Single line functions are cool, but mind the comma and the colon!" do
-    assert multiply(2, ___) == 6
+    assert 6 == multiply(2, ___)
   end
 
   def first(foo, bar), do: "#{foo} and #{bar}"

lib/koans/09_enums.ex

@@ -6,7 +6,7 @@ defmodule Enums do
   end
 
   koan "Depending on the type, it counts pairs" do
-    assert Enum.count(%{ :a => :foo, :b => :bar}) == ___
+    assert Enum.count(%{ a: :foo, b: :bar}) == ___
   end
 
   def less_than_five?(n), do: n < 5

lib/koans/10_processes.ex

@@ -30,9 +30,8 @@ defmodule Processes do
   koan "Waiting for a message can get boring" do
     parent = self()
     spawn(fn -> receive do
-                   _anything -> flunk "I really wasn't expecting messages"
                 after
-                  10 -> send parent, {:waited_too_long, "I am impatient"}
+                  5 -> send parent, {:waited_too_long, "I am impatient"}
                 end
            end)
 

lib/koans/11_tasks.ex

@@ -25,7 +25,9 @@ defmodule Tasks do
                              :timer.sleep(100)
                              3 * 3
                          end)
-    assert Task.shutdown(handle) == ___
+    %Task{pid: pid} = handle
+    Task.shutdown(handle)
+    assert Process.alive?(pid) == ___
   end
 
   koan "Shutdown will give you an answer if it has it" do

lib/koans/12_agents.ex

@@ -27,10 +27,10 @@ defmodule Agents do
   end
 
   koan "Somebody has to switch off the light at the end of the day" do
-    Agent.start_link(fn() -> ["Milk"] end, name: __MODULE__)
+    {:ok, pid} = Agent.start_link(fn() -> ["Milk"] end, name: __MODULE__)
 
-    result = Agent.stop(__MODULE__)
+    Agent.stop(__MODULE__)
 
-    assert result == ___
+    assert Process.alive?(pid) == ___
   end
 end