Implement `has_env' condition keyword

features/tests/has_env.feature

@@ -0,0 +1,32 @@
+@sshd
+Feature: `has_env' condition keyword
+
+  Scenario: succeeds when remote environment variable is defined
+    Given a recipe with:
+      """
+      target 'some_host.test'
+
+      task :testing_env_var_definition do
+        condition { has_env :shell }
+
+        echo 'evaluated'
+      end
+      """
+    When I execute the recipe
+    Then the exit status must be 0
+    And the output must contain "evaluated"
+
+  Scenario: fails when remote environment variable is not defined
+    Given a recipe with:
+      """
+      target 'some_host.test'
+
+      task :testing_env_var_definition do
+        condition { has_env :inexistent_var }
+
+        echo 'evaluated'
+      end
+      """
+    When I execute the recipe
+    Then the exit status must be 0
+    And the output must not contain "evaluated"