Implement `test_macro' recipe keyword

features/recipe_test_macro.feature

@@ -0,0 +1,52 @@
+Feature: `test_macro' recipe keyword
+
+  Scenario: declares a new test keyword
+    Given a recipe with:
+      """
+      test_macro :even? do |n|
+        n % 2 == 0
+      end
+
+      [1, 2].each do |n|
+        task "test_macro-even-#{n}" do
+          condition { even? n }
+          echo n
+        end
+      end
+      """
+    When I successfully execute the recipe
+    Then the output must contain "2"
+    And the output must not contain "1"
+
+  @sshd
+  Scenario: has access to core tests
+    Given a recipe with:
+      """
+      target 'some_host.test'
+
+      test_macro(:other_env?) { |k| env? k }
+
+      [:shell, :non_existent_var].each do |k|
+        task "test_macro-condition-#{k}" do
+          condition { other_env? k }
+          echo "#{k}_ok"
+        end
+      end
+      """
+    When I successfully execute the recipe
+    Then the output must contain "shell_ok"
+    Then the output must not contain "non_existent_var_ok"
+
+  Scenario: has access to other tests declared with `test_macro'
+    Given a recipe with:
+      """
+      test_macro(:one?)       { |e| e == 1 }
+      test_macro(:one_alias?) { |e| one? e }
+
+      task :test_macro_macro do
+        condition { one_alias? 1 }
+        echo 'one_alias_ok'
+      end
+      """
+    When I successfully execute the recipe
+    Then the output must contain "one_alias_ok"