Add NullExampleFilter

spec/null_example_filter_spec.cr

@@ -0,0 +1,11 @@
+require "./spec_helper"
+
+describe Spectator::NullExampleFilter do
+  describe "#includes?" do
+    it "returns true" do
+      example = PassingExample.create
+      filter = Spectator::NullExampleFilter.new
+      filter.includes?(example).should be_true
+    end
+  end
+end

src/spectator/includes.cr

@@ -33,6 +33,7 @@ require "./example_filter"
 require "./source_example_filter"
 require "./line_example_filter"
 require "./name_example_filter"
+require "./null_example_filter"
 
 require "./example_failed"
 require "./expectation_failed"

src/spectator/null_example_filter.cr

@@ -0,0 +1,9 @@
+module Spectator
+  # Filter that matches all examples.
+  class NullExampleFilter < ExampleFilter
+    # Checks whether the example satisfies the filter.
+    def includes?(example)
+      true
+    end
+  end
+end