Add example for producing errors

spec/helpers/errored_example.cr

@@ -0,0 +1,22 @@
+# Example that always raises an exception.
+class ErroredExample < Spectator::RunnableExample
+  # Dummy description.
+  def what
+    "ERROR"
+  end
+
+  # Run the example that always produces an error.
+  private def run_instance
+    raise "Oops"
+  end
+
+  # Creates an errored example.
+  def self.create
+    hooks = Spectator::ExampleHooks.empty
+    group = Spectator::RootExampleGroup.new(hooks)
+    values = Spectator::Internals::SampleValues.empty
+    new(group, values).tap do |example|
+      group.children = [example.as(Spectator::ExampleComponent)]
+    end
+  end
+end