Add ExampleFilter class

spec/example_filter_spec.cr

@@ -0,0 +1,85 @@
+require "./spec_helper"
+
+def new_filter(criterion)
+  criteria = ["BOGUS", -1, criterion, /^$/, Spectator::Source.new(__FILE__, __LINE__)]
+  Spectator::ExampleFilter.new(criteria)
+end
+
+describe Spectator::ExampleFilter do
+  describe "#includes?" do
+    context "with a matching Regex" do
+      it "is true" do
+        example = new_runnable_example
+        regex = Regex.new(Regex.escape(example.what))
+        filter = new_filter(regex)
+        filter.includes?(example).should be_true
+      end
+    end
+
+    context "with a non-matching Regex" do
+      it "is false" do
+        example = new_runnable_example
+        regex = /BOGUS/
+        filter = new_filter(regex)
+        filter.includes?(example).should be_false
+      end
+    end
+
+    context "with a String equal to the name" do
+      it "is true" do
+        example = new_runnable_example
+        filter = new_filter(example.to_s)
+        filter.includes?(example).should be_true
+      end
+    end
+
+    context "with a String different than the name" do
+      it "is false" do
+        example = new_runnable_example
+        filter = new_filter("FAKE")
+        filter.includes?(example).should be_false
+      end
+    end
+
+    context "with a matching source location" do
+      it "is true" do
+        example = new_runnable_example
+        filter = new_filter(example.source)
+        filter.includes?(example).should be_true
+      end
+    end
+
+    context "with a non-matching source location" do
+      it "is false" do
+        example = new_runnable_example
+        source = Spectator::Source.new(__FILE__, __LINE__)
+        filter = new_filter(source)
+        filter.includes?(example).should be_false
+      end
+    end
+
+    context "with a matching source line" do
+      it "is true" do
+        example = new_runnable_example
+        filter = new_filter(example.source.line)
+        filter.includes?(example).should be_true
+      end
+    end
+
+    context "with a non-matching source line" do
+      it "is false" do
+        example = new_runnable_example
+        line = example.source.line + 5
+        filter = new_filter(line)
+        filter.includes?(example).should be_false
+      end
+    end
+
+    context "with an empty criteria" do
+      it "is true" do
+        filter = Spectator::ExampleFilter.new
+        filter.includes?(new_runnable_example).should be_true
+      end
+    end
+  end
+end

src/spectator/example_filter.cr

@@ -0,0 +1,24 @@
+module Spectator
+  # Checks examples to determine which should be run.
+  class ExampleFilter
+    # The criteria for filtering examples can be multiple types.
+    # A `String` will exact-match an example's name.
+    # A `Regex` will perform a regular expression match on the example's name.
+    # A `Source` will check if the example is in the specified file on a given line.
+    # An `Int32` will check if an example is on a given line.
+    alias Type = String | Regex | Source | Int32
+
+    # Creates the example filter.
+    # The *criteria* should be a list of what to filter on.
+    def initialize(@criteria = [] of Type)
+    end
+
+    # Checks if an example is in the filter, and should be run.
+    def includes?(example)
+      return true if @criteria.empty?
+      @criteria.any? do |criterion|
+        example === criterion
+      end
+    end
+  end
+end

src/spectator/includes.cr

@@ -28,6 +28,7 @@ require "./config"
 require "./config_builder"
 require "./config_source"
 require "./command_line_arguments_config_source"
+require "./example_filter"
 
 require "./example_failed"
 require "./expectation_failed"