Implement `has_executable' condition keyword

features/tests/has_executable.feature

@@ -0,0 +1,30 @@
+@sshd
+Feature: `has_executable' condition keyword
+
+  Scenario: succeeds when remote executable is available
+    Given a recipe with:
+      """
+      target 'some_host.test'
+
+      task :testing_executable_availability do
+        condition { has_executable 'true' }
+
+        echo 'evaluated'
+      end
+      """
+    When I successfully execute the recipe
+    Then the output must contain "evaluated"
+
+  Scenario: succeeds when remote executable is available
+    Given a recipe with:
+      """
+      target 'some_host.test'
+
+      task :testing_executable_availability do
+        condition { has_executable 'some_non_existent_executable' }
+
+        echo 'evaluated'
+      end
+      """
+    When I successfully execute the recipe
+    Then the output must not contain "evaluated"